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SPON, 48, CHARING CROSS., M DCCCLXYII. - [The Right of Translation is reserved.| de LONDON : ort R. CLAY, SON, AND TAYLOR, PRINTERS, ; BREAD STREET HILL, Ob7.2 ps4 HENRY HUSSEY VIVIAN, Eso, M.P., THIS WORK, TREATING OF SOME OF THE BRANCHES OF AN ART WHICH HIS FAMILY HAS FOR A LONG PERIOD SUCCESSFULLY PRACTISED, AND WHICH ‘HE HAS HIMSELF SO GREATLY CONTRIBUTED TO ADVANCE, IS RESPECTFULLY DEDICATED BY LE “AU LHORS oO y f 14, ha = AA 3 Ss AGS oe. pee ve a cgaad a d el cw ate Ot ee THIs treatise has been undertaken with the hope that it may, to some extent, supply a want in our technical literature, which is very deficient in books treating of the mining and metallurgy of the precious metals. In preparing this work for publication, care has been taken to obtain data directly from the best and most authentic sources, The connexion of the author, as a Mining Engineer, with various large metallurgical establishments, together with his repeated visits to, and residence in, some of the principal mining districts of both Europe and America, have afforded him many opportunities for observation and investigation. His object has rather been to render this volume practically useful as a record of well-authenticated facts, and of the results of actual experience, than to advance new theories, or to accumulate additional evidence in support of old ones. He has, therefore, contented himself with merely stating the results both of his own observations, and those of others; or at most with suggesting the nature of the forces producing the effects described. He believes that our knowledge of chemical geology is not, as yet, sufficiently advanced to warrant an attempt to form a general theory of the formation of mineral veins. b 2 Wie PREFACE. Zecent observations and experience appear, however, to lead to three important conclusions. First, that the most productive gold- bearing rocks are by no means exclusively confined to the Silurian period; secondly, that aqueous agencies have been, and still are, actively at work in the formation of mineral deposits ; and, thirdly, that gold ledges are not more liable than ordinary metalliferous veins to become impoverished. in depth. The general order adopted has been, first to describe, in each instance, the principal gold and silver producing districts, and to give such statistical information as could be obtained respecting their yield and importance. Then follows an. account of the methods employed for extracting the ores; and, lastly, a description of the apparatus made use of for their mechanical and metallurgical treatment. With regard to the yield of silver from the various districts producing ores of that metal, it may be remarked that, in a few instances, it has been found necessary to depart from the official estimates; since ores raised in one country have been metallurgically treated in another, and the resulting metal has consequently figured m the returns of both. The information derived either from other books or from private sources, has, in most instances, been duly acknowledged; but the Author takes this opportunity of returning thanks to his friends for many valuable suggestions of too general a character to admit of specific mention in the body of the work. He is under especial obligations to the Messrs. Taylor, of London; Mr. T. EF. Cronise and Mr. P. N. McKay,’ of San Francisco; Mr. W. Watt, of Grass Valley ; and to the gentlemen of the State Geological Survey of California. He also takes this opportunity of expressing his thanks. to the principal mill owners and mining engineers of California and Nevada; without the facilities which these gentlemen have so kindly PREFACE, 1X afforded, the Author would have been unable to give the very large amount of facts relating to the mines of the Pacific Coast which their liberality has enabled him to collect. The table and formule on page 236 have been contributed by Mr. C. W. Merrifield, F.R.S., to whom, and to Mr. F. W. Rudler, the author begs to return his thanks for assistance rendered whilst the book was passing through the press. KENSINGTON, July, 1867. GONG Na back: GOLD. CHAPTER I. MODE OF OCCURRENCE, AND GEOLOGICAL POSITION. Analyses of Native Gold—Age of Auriferous Rocks—Gold of the Jurassic Period —Quartz Veins of recent Formation—Gold Veins not impoverished in Depth --plinywel Deposits.) 8. Sk ° ° . ° ° ° CHAPTER II. GOLD REGIONS OF THE OLD WORLD. Great Britain and Ireland—France—Spain and Portugal—Italy—Switzerland— Holland—Russian Possessions — Germany—Austrian Empire—Central and Southern Asia—China and Japan—Africa CHAPTER III. UNITED STATES OF AMERICA—ATLANTIC OR APPALACHIAN GOLD FIELDS. Discovery of Gold in the Southern States — Virginia— North Carolina—South Carolina—Georgia—Tennessee and Alabama—Description of Appalachian Gold Fields—Principal Gold Mines of the Southern States . CHAPTER IV. UNITED STATES OF AMERIUA--GOLD FIELDS OF THE PACIFIC COAST. Discovery of Gold in California—Situation and Extent of Auriferous Districts— Shallow and Deep Placers—Quartz Veins—Mariposa—Tuolumne—Calaveras— Amador—E] Dorado—Placer—Nevada and Sierra. Counties, &e.—Statistics of Gold produced in the United States PAGE 37 Xil CONTENTS. CHAPTER V. MEXICO, CENTRAL AMERICA, AND SOUTH AMERICA. PAGE - Mexico pre-eminently a Silver-producing Country—Nicaragua—Chontales Mining Company—Brazil—St. John d’El Rey Company—Imperial Brazilian—Don Pedro North d’Ei Rey—Rossa Grande Gold Mining Company—East d’E] Rey—New Granada—Mariquita and New Granada Mining Company— Peru and Bolivia . CHAPTER VI. BRITISH POSSESSIONS—NORTH AMERICAN COLONIES. Discovery of Gold in Nova Scotia—Geology of Gold Region—Corrugated Quartz at Waverly —Impracticable Mining Laws— Statistics of Gold obtained — Canadian Gold Fields— Principal Gold Washings in Canada— Report of Parliamentary Committee—Discovery of Gold in British Columbia—Extent - of the Gold Fields—Gold chiefly obtained from Alluvial Diggings CHAPTER VII. BRITISH POSSESSIONS—AUSTRALIA AND NEW ZEALAND. Discovery of Gold in Australia—Victoria the most productive Division of the Placer Mining—The Pan—Rocker— Long Tom— Puddling Box—Sluice— River Mining —Beach Mining— Water Supply—Eureka Canal—Hydraulic Mining— Amount of Water required—Cost of Water, and Method of Measurement— Dry ashing i os Pe web en ee te Bee) eee Australian -Continent—Geology of the Gold-bearing Rocks of Victoria—Quartz Veins—Auriferous Pliocene Gravels—Primitive Mining—Quartz Veins pro- ductive at all Depths yet attained —Port Phillip and Colonial Gold Mining Company—Yield of some of the- Principal Mines—Total Amount of Gold exported from Victoria—Gold exported from New South Wales— South Australia and Tasmania—Queensland—Discovery of Gold in New Zealand— Principal Gold Fields of that Country—Yield of Gold—Annual Production of the Gold Mines of.the World ooh ne ik ce a ie CHAPTER “VIII. GOLD WASHING IN CALIFORNIA AND AUSTRALIA. =F “I 91 101 12 § ee eer Sc diced CONTENTS. CHAPTER IX. VEIN MINING IN CALIFORNIA AND AUSTRALIA. Quartz Mining—Testing Gold Quartz— Batea—Horn Spoon—Arrastre—Chilian Mill—Stamping Mill—Amalgamating in Battery—Iron Battery Box—Screens — Single Cams—Separation of Gold—Blankets—Amalgamated Copper Plates —Cleaning up—Settling Pits—Amalgamator—Attwood’s System of Amalga- mation—Loss of Gold—Concentration of Tailings—Rocker—Concave Buddle — Bradford’s Separator — Extraction of Gold from Sulphides— Baux and Guiod’s Amalgamator—Chlorination Process—Analyses of Californian Pyrites -—Retorting—Melting—Tabular Statement of the Operations of the principal eeeorminre Sati Milde os og. aes we, beady os CHAPTER X. VEIN MINING IN HUNGARY AND BRAZIL—SODIUM AMALGAM. Auriferous Veins at Schemnitz—Stamping Mills—Hungarian Bowls—Shaking Tables—Concentration of Auriferous Slimes—Goldliitte—Scheidetrog—Results obtained—Mode of Occurrence of Gold at Morro Velho—Stamping—Strakes —Treatment of First Tailings—Treatment of Second Tailings—Amalgamation of concentrated Ores— Loss of Gold and Mercury-—Cost of Working —- Application of Sodium Amalgam—Not generally employed in California— Advantages stated to result from its Use \ CHAPTER XI. ASSAY OF AURIFEROUS ORES—ESTIMATION OF GOLD CONTAINED IN QUARTZ— REFINING— ASSAY OF GOLD BULLION. Assay of Gold Quartz—Fusion with Litharge or Red Lead—Auriferous Pyrites— Cupellation— Inquartation—Parting—Assay Table—Table showing Proportion of Gold in Auriferous Quartz—Refining—Platinum Vessels—Cast Iron Pans— Assay of Bullion—Quantity of Lead necessary for Cupellation of Alloys of Gold and Copper—Assay Laboratory—The Touchstone . ee Xlil PAGE 165 203 226 — SILVER. CHAPTER All. MODE OF OCCURRENCE AND GEOLOGICAL POSITION. Native Silver—Antimonial Silver—Native Amalgam-— Principal Silver Ores Sulphides—Arsenides —Selenides—Tellurides— “Chloride—lodide —Bromide— Carbonate—Silicate—-Chief Sources of Silver—Geological Position CHAPTER XIll. -RINCIPAL SILVER MINES OF THE OLD WORLD. Silver Mines of the United Kingdom—Norway—Sweden—Transylvania and the Banat—Saxony and Bohemia—Mines of the Hartz—Silver Mines of the Alps —France—Spain—Altai Mountains—Daouria . CHAPTER: XIV. SILVER MINES OF NORTH AMERICA. Principal Mining Districts of Mexico—-Production of Silver in Mexico up to 1845 Produce of Ores treated —Guanaxuato— Zacatecas — Fresnillo— Real del Monte—History and Operations of the Real del Monte Mining Company— Principal Mining Districts of Nevada—Comstock Vein—Discovery of Silver at, Virginia— Yield during Four Years—Sutro Tunnel— Reese River Distriet— Systems of Veins—Amador District—Rav Washington— Union—Smoky Valley—Twin River—San iGatontie tobe: Ming Districts Table showing Number of Reduction Works, &c. «cee CHAPTER XV. CENTRAL AMERICA AND SOUTH AMERICA. Guatemala—Mines of the Central American Mining Company—Mining District of Alotepec—Produce of Silver—South America Annual Pro- duction of Silver—Bolivia—Mines of Potosi--Their Production of Silver— Chili—Mines of Coquimbo—Annual Production of Chili—New Granada— Santa Ana Mines—Table showing Production of Silver in various Countries PAGE 247 252 311 CONTENTS. XV CHAPTER XVI. TREATMENT OF SILVER ORES BY AMALGAMATION—PATIO PROCESS, dc. PAGE Patio Process—Magistral—Salt—Mercury— Lime— Copper Precipitate—Compo- sition of Ores—Rough Stamping—Fine Grinding—Raspar—Loss of Gold— The Patio—Incorporar—Treading of Torta—Washing—Straining Amalgam— Distillation—Loss of Silver—Loss of Mercury—Chemical Reactions of the Patio—Results of the Patio Process—At Guanaxuato—Fresnillo—Real del Monte—Virginia City—Amalgamation by Hot Process—Estufa Amalgamation 321 CHAPTER XVII. TREATMENT OF SILVER ORES BY AMALGAMATION—BARREL PROCESS. Freiberg — Barrel Amalgamation— When introduced — Composition of Ores — Chlorination—Amalgamation—Distillation of Amalgam—Refining—Constante —Grinding Crude Ores—Calcining with Salt—Sifting and Grinding—Amal- gamation at Constante—Treatment of Amalgam—Melting and Refining— Treatment of Residues—Cost of treating Ores at Constante-—Cost at Real del Monte—The Barrel Process in Nevada—Method of conducting, and Cost of eee Oe ae eh ge, CHAPTER XVIII. TREATMENT OF SILVER ORES BY AMALGAMATION—PAN PROCESS. Stamping—Common Pan—Varney’s Pan—Wheeler’s Pan—Hepburn and Peter- son’s Pan — Separators — Working in Pans — Retor ting — Arrangement of Reduction Works—Treatment of roasted Oresin Pans. . . . . .t . 390 CHAPTER XIX. TREATMENT OF ARGENTIFEROUS ORES AND PROD UCTS BY SOLUTION AND PRECIPITATION. Augustin’s Process—Roasting with Salt—Lixiviation and Pr ecipitation—Ziervogel’s Process—Roasting—Solution of Sulphate of Silver — Precipitation of Silver by Copper—Von Patera’s Process—Roas sting with Common Salt—Solution of Chloride of Silver in Hyposulphite of Ae deat ee Sulphide of Sodium—Treatment of Sulphide of Silver. . .. : St huh ae a0 CHAPTER XX. CONCENTRATION OF THE PRECIOUS METALS IN METALLIC LEAD—SMELTING. Preliminary Observations—Smelting Auriferous Silver Ores for Matts—Extraction of the Precious Metals in Bath of fused Lead—Concentration of Silver in Matts, and Fusion with roasted Lead Ores, without Addition of Iron— Reduction of unroasted Lead Ores by Metallic Iron—Castillian Furnace— Reduction of partially roasted Lead Ores by Metallic Iron—Results obtained ee es 8G XvVl CONTENTS. CHAPTER XXI. EXTRACTION OF THE PRECIOUS METALS FROM ARGENTIFEROUS AND AURIFEROUS LEAD OBTAINED BY SMELTING. PAGE Continental Process of Cupellation — Refining Silver obtained from Cupel — English System of treating Argentiferous Lead—Calcination—Concentration of Silver by Crystallisation—Pattinson’s Process—French Process—Refining enriched Lead-—Costs and Results of Desilverising—Liquation . . . . . 448 CHAPTER XXII. TREATMENT OF ARGENTIFEROUS GALENA AT PONTGIBAUD. Preparation of Lits de Grillage—Roasting—Preparation of Lits de Fusion— Smelting in Castillian Furnace — Improving or Calcining— Crystallisng— Refining—Reducing—Re-smelting Rich Slags—Roasting Matts—Treatment of Calcined Dross—Treatment of Lead Cinder—Treatment of Lead Fume—Losses of Lead and Silver-—Summary of Costs. . . <2. 9s ss ye ge eee CHAPTER XXIII. SMELTING SILVER ORES IN MEXICO. Roasting—Fusion—Cupellation—Vaso—Galeme— Nufla . eee CHAPTER XXIV. ASSAY OF SILVER ORES AND BULLION. Argentiferous Galena—Assay of Silver Ores Proper—Scorification—Cupellation— ‘Assay/Table—Assay of Silver Bullion . . . . -. «(> > » c)Qeeeeeueemnemes Appendix. ee ae eS Index asc ee i ee a = i Q OID OT BH 89 bo pe LIST OF WOODCUTS. The Morro Velho Mine, Brazil . . . . . , Frontispiece. Diggings at the Soimanofsk Mines . Section at Maine Boy’s Tunnel . Tunnels under Table Mountain . Corrugated Quartz, Laidlaw’s Farm Clunes, North Cross Section . 5 South i Washing with Pan . Section of Cradle = Washing with Cradle . Section of Tom and Riffle Box Plan “3 t Plan of Sluice nie Section s. Zig-zag Riffles Under-current Sluice Tail Sluices, Yuba River . Flume near Smartsville Pressure Box, Yuba River ; : Hydraulic Mining, Washing down Bank Sluice and Tunnel, Tim iwetoo Iron Pipes Batea ; Horn, showing Method a Gaeta Spook Arrastre Pic ye Stamp Grate, ie Honan Holes es 29 Oblong ” Transverse Section of ion Battery Bas Elevation of Iron Battery Box Single Cam 5 Section of Blanket Peanie Section of Washing Tank . Section of Amalgamator Plan Section of Contave Buddle Plan - ; Baux and Guiod’s Canta Melting and Assay Furnace . Assay Ee varcior Section of Comstock Vein PAGE 23 44 45 93 114 115 1338 134 134 138 138 141 141 145 147 148 154 156 157 159 162 167 168 169 Wis 175 176 176 177 180 182 185 185 192 193 196 229 243 291 Xvill LIST OF WOODCUTS. Patio at the Gould and Curry Patio at Guanaxuato Washing Apparatus emplcyel at ieee Manga or Strainer Sa Mould containing Brick of Aiea ; Lifting the Capellina Capellina . . Sectional Blevation a yee Bares Plan of Amalgamating Barrels . a © Vertical Section of Revolving Calciner Horizontal ,, ‘5 os Horizontal Mills . : Vertical Section of Common Pan Plan of Common Pan Wheeler’s Pan ; Hepburn and Peterson’s ee Front Elevation of Retort Longitudinal Section of Retort . Lixiviating Tub . Zier vogel’s Process, Arne of ones: Von Patera s Process, rv = Clausthal Furnace, Vertical Section : Section through Tuyere . be J 33 Rlevaiion of Castillian Furnace . Vertical Section % Horizontal Section = Vertical Section of Cupelling Haranee: Horizontal Section ~ Plan of Crystallising Pots Elevation of eS , Pot and Crane . 73 = Refinery . , Horizontal Section of ener © Vertical ss Elevation of Roasting ne Penksilead : Horizontal Section a a Vertical + zs Elevation of Castillian Wituace # Side View of Slag Waggon = End 2 29 29 Plan of a oa Improving Furnace— Elevation Be Horizontal Section oe Section through Tap Hole = n Horizontal Section through Tuyeres ‘ VIL REFERENCE TO PLATES, erc. Map of the Grass Valley Mining District, California . . To follow Page Ten-Stamp Battery. . . . ¥ System of Blankets and Rifles Sear at ee DSRS OTe: Cee tea tell in SIH) ec wh a a ile ch cet lo sea odes 8 RF Attwood’s Amalgamator . . . ne Machinery employed for the faced of ( told at Se ea nitz, Lower Hungary . . ; . a Amalgamating Machinery, Maes Velho Mine, noe , ‘4 Varney’s Amalgamating Pan... as re Elevation of Silver Reduction Works, eee Nevada : F CHAPTER I. MODE OF OCCURRENCE AND GEOLOGICAL POSITION. ANALYSES OF NATIVE GOLD—AGE OF AURIFEROUS ROCKS—GOLD OF THE JURASSIC PERIOD—QUARTZ VEINS OF RECENT FORMATION—GOLD VEINS NOT IMPOVERISHED IN DEPTH—ALLUVIAL DEPOSITS. 4 MopbE oF OccuRRENCE.—This metal occurs in the following forms :— ALLOYS, Native Gold.—An Alloy of Gold and Silver, associated with small quantities of copper, iron, and other metals. Palladivwm Gold.—Gold and Palladium—Porpezite. Rhodium Gold.—Gold and Rhodium. AMALGAM. Gold Amalgam.—A native Amalgam of Gold and Mercury. ORES. Sylvanite, or Graphic Tellurium.—Telluride of Gold and Silver. Nagyagite.—Telluride of Lead containing Gold, Silver, and Copper. Of the foregoing combinations, Native Gold is the only one of great commercial importance, as furnishing nearly the whole of this metal annually obtained from the different gold-producing districts of the world. Palladium gold oceurs to some extent in the mines of Gongo Soco in Brazil, and a small quantity of graphic tellurium is found in those of Transylvania. The other native alloys of gold can only be regarded in the light of mineralogical curiosities. Gold is usually found, in alluvial washings, in the shape of fine particles and water-worn plates and scales, but crystallised specimens B 2 GOLD. are occasionally met with. These crystals, which are usually small, are generally in the form of octahedrons, although Shepard describes a pentagonal dodecahedron, from California, two-fifths of an inch in diameter: an octahedral crystal from the same country, described by F, Alger, had a diameter of eight-tenths of an inch. | Native gold, occurring in veins, is most frequently foul in a quartzose gangue, in which it is often associated with iron and copper pyrites, arsenical pyrites, blende and galena. Gold and iron pyrites are very intimately associated, although the gold appears always to exist in the metallic state, since in almost every gold- — producing district, when sulphide of iron has become decomposed, by weathering, into hydrated oxide of iron, gold becomes apparent, and is readily separated by washing. When this metal is encased in undecomposed copper pyrites, iron pyrites, or any other sulphide, or arsenide, its separation, either by washing or amalgamation, is attended with considerable difficulty, although the whole of the gold may be readily extracted by smelting the concentrated pyrites, either with lead ore, or with htharge. The gold found in ordinary gold quartz, in addition to being disseminated in a more or less finely divided state in the associated sulphides, presents itself in threads, thin plates, and grains of varying dimensions. These are not unfrequently apparent to the naked eye, but rock showing no traces of visible gold is often sufficiently rich to yield a large profit after deducting working expenses. Native gold invariably contains a certain amount of silver, and almost always traces of copper and iron. The silver associated with native gold is not combined with it according to the laws of atomic proportion, but forms with it an alloy in which silver re- presents from one-hundredth to more than one-half the total weight of the mixture. The gold of Australia averages from 960.to 966 thousandths fine, whilst that of California contains from 875 to 885 thousandths of pure gold. The composition of native gold from various localities is given in the following table :— MODE OF OCCURRENCE. TABLE Showing the Composition of various Samples of Native Gold. — Locality. Russtan Emprre— Petropawlowsk washings Boruschkoi hk Cree: Zarewo-Nicolajewsk,near Miask, washings . . , Berezovsk Mine, in matite . te a: Berezovsk, in quartz . brown He TRANSYLVANIA— Sta. Barbara Mine, at Fiises, scales in porphyry with quartz Vorospatak, in quartz . AUSTRALIA— South Australia Bathurst . Ballarat New ZEALAND— Locality not known W ALES— Vigra and Clogau . ; Welsh Gold Mining Co. . British Cotumpra— Locality not given . Stephens Creek Cariboo Soutn AMERICA— Marmato . a: Henge Antioquia, New Granada, wash- ings . Sie Brazil . Unirep States anp Canapa— Feather River, California, scales American Fork,California, scales Mariposa Estate, Quartz Gold. La en Riviere du Loup, Canada porphyry with | Analyst. Gold. | Silver. G. Rose | 86°81 | 13°19 f 83°85 [16°15 A 89°35 |10°65 : 93°78 | 5:94 re 91°88 | 8°03 re 84°89 | 14°68 | R 60°49 | 38°74 _ 14.8. Thomas! 87°78 | 6-07 . |J. H. Henry| 95°69 | 3:92 F. Claudet |99°-25 | 0-65 » {96:25 | 3°55 i 88:50 | 5-00 . (76°40 | 22-70 ip 86°10 | 13°50 bebe 79°50 |19°70 bess 84:25 | 14:90 Boussingault) 73°45 | 26°48 m 64°93 | 35°07 D’Arcet.. {94°00 | 5°85 Rivot 89°10 | 10°50 ; 90:90 | 8°70 F. Claudet | 81:00 | 18°70 W.W. Mather) 95°579|) 4:42] T. S. Hunt | 86°40 | 13-60 Copper.| Iron. Trace | Trace. bP) 99 99 9 0°08 | 0:04 0°09 | Trace. 0°04 | 0°13 0°77 6°15 0°16 0°20 0:20 | Trace ice: bb) 99 4 GOLD. The larger pieces of water-worn gold are called by the miners nuggets ; but these seldom exceed a few pounds in weight, and are generally accompanied by more or less of the quartzose gangue forming the original veinstone. One of the finest lumps of native gold now in existence, is that preserved in the collection of the Russian School of Mines, which weighs about 97 lbs. The largest piece of gold ever found, was probably the great Australian nugget known as the “Sarah Sands,” which «weighed 233 |bs. 40z. troy. GEOLOGICAL Position or GoLp.—The general characteristics of the gold-bearing rocks throughout the world are exceedingly alike, since, whatever their original structure or composition may have been, they have become so assimilated by metamorphic action as to exhibit a very striking resemblance to each other, They generally consist of slaty deposits, frequently talcose, although sometimes chloritic or argillaceous, and in these the gold-bearing quartz, which is the almost universal matrix of this metal, is generally found most productive. Valuable gold veins are also occasionally found in granite, gneiss and syenite, but these do not so often form the enclosing rock as the metamorphosed shales and slates above referred to. Veins of auriferous quartz have most frequently the same strike - and dip as the shales in which they are enclosed, but in some instances they not only intersect the shales at varying angles, but have also a separate and independent dip. When rocks remain stratified, in nearly the same position in which they were originally deposited, they are rarely found to be highly auriferous; but when, on the contrary, they have been invaded by eruptive masses, are broken up, or raised on edge, and have assumed a crystalline texture, there is good reason to anticipate the presence of the precious metal. : Generally speaking, it may be said that a considerable proportion of the gold-bearing rocks of the world belong to the two lowest geological groups, the azoic and paleeozoic, or rather to the latter. For although we are not aware that rocks proved to be azoic have been found to be auriferous, yet it is often impossible to distinguish between these two groups, since in localities where the formation is GEOLOGICAL POSITION. ie be N i eae 2 metalliferous, the strata have generally so changed their original===-~ character, as to render it exceedingly difficult to recognise their exact position in the geological series.* The metamorphosed auriferous strata of the Ural Mountains have been shown by Sir Roderick Murchison to be paleozoic, and the Australian rocks, associated with veins of auriferous quartz, have also afforded abundant evidence of Silurian origin. Mr. Selwyn, the director of the Colonial Geological Survey, has fully satisfied himself that the gold-bearing veins of Victoria are confined to rocks of the paleeozoic age, chiefly to those belonging to the Lower Silurian divi- sion, ascending from the Llandeilo to the Upper Caradoc formation inclusive. Arguing from his own experience in the Ural Mountains and elsewhere, as well as from facts collected by other observers in the various gold-producing countries of the world, Sir R. Murchison _ became impressed with the conviction that all the more productive auriferous rocks belong to the paleeozoic period, and he considers this question so fully settled, that he remarks, “My chief article of belief has now proved to be true, namely, that the rocks which are most auriferous are of Silurian age.”+ It would appear, how- ever, that the gold-producing rocks of California and Nevada present a remarkable exception to this general rule, since Professor Whitney, the State Geologist of California, has collected numerous fossils of undoubted Jurassic origin, found 7 situ, in the immediate proximity of one of the largest and best defined quartz veins of the Pacific coast. When describing the geology of the district in the vicinity of the Pine Tree vein, which is one of the largest comprehended within the limits of the Mariposa Estate, he remarks :+ “ Within the slate formation are interstratified sandstones, which are, in some cases, very distinctly bedded, as for instance on the west slope of Hell Hollow. The beds are often several feet in thickness, and like the slates themselves, in all stages of alteration, as is made evident by the differences of hardness, colour and texture which they exhibit. The region of least metamorphism seems to have been from the Pine Tree mine, west, to the slope of Juniper Ridge, and southward, to near the village of Bear Valley. It was in this region that Mr. King * The Discovery by Sir William Logan of fossil remains in the Lower Laurentian rocks of Canada, renders it extremely doubtful whether the term azote can be correctly applied, even to the oldest formations known to geologists. ¢ Siluria, p. 474. + Geological Survey of California, p. 226. 6 GOLD: found in situ fossils, by which the age of this formation was clearly made out to be Jurassic.”* The period of the formation of auriferous veins is less readily determined than the age of the enclosing rocks, although they may be presumed to have often originated at the time of the metamorphic action, by which the change in the strata themselves was effected. It is, however, tolerably evident that this action has not been confined to any particular geological epoch, and it would appear that these * The following description of fossils from the auriferous slates of California, is by F. B. Meek; see Appendix, Vol. I. Geological Survey of California, p. 477. “The fossils from the auriferous slates, collected. on the Mariposa Estate, having been by mistake sent for investigation in part to Mr. Gabb, and in part to the writer, were regarded by both of us, independently, as most probably of Jurassic age. This opinion was expressed by Mr. Gabb in a communication to the California Academy of Sciences, in November 1864 (see Proceed. Vol. III. p. 172), and by myself at about the same time in a communication to the State Geologist. In his paper alluded to above, Mr. Gabb described the following species, viz., Lima Erringtoni, Pholadomya orbiculata, and Belemnites Pacificus. He like- wise mentioned a Pecten, and a Nucula or Leda. Two of these species were also described by the writer, under other names, in a communication prepared for publication, but fortunately not published. “As ib was considered by the State Geologist desirable that I should examine all of the few fossils yet found in these slates, they were placed in my hands for investigation ; and drawings and descriptions have been prepared for publication. “In examining the specimens formerly sent, much difficulty was experienced in determining the generic relations of two or three bivalves resembling an oblique Inoceramus, and varying considerably from each other in form and con- vexity, but agreeing exactly in surface markings. Being all casts, more or less compressed and otherwise distorted, it was difficult to understand how they could belong to one species, as their surface markings and some other points of resem- blance seemed to indicate, though this was suspected to be the case. Amongst the collections subsequently sent on, and now under examination, these same forms are observed. One is an obliquely oval rather convex shell, with a very prominent terminal strongly incurved beuk, while the other is much more com- pressed, with a straighter, dorsal outline, and a beak scarcely distinct from the cardinal margin. On examining the collections more recently received it was soon observed that the compressed specimens with an inconspicuous beak, are all right valves, while all of those with a prominent strongly incurved beak are left, valves. “This fact, together with their other characters, leave little room for doubting that these are the cpposite valves of one or two species of the genus Aucella. As this genus is, so far as known, entirely confined to the Jurassic rocks, while an Amussium-like shell from the same slates is closely allied to a Jurassic species, and the genus Belemnites is not generally regarded as dating back beyond the com- mencement of the Jurassic period, I can scarcely entertain a doubt that these gold- bearing slates really belong to that epoch, and probably to some of its lower members, at which horizon most of the known European species of Aucella are said to occur.” GEOLOGICAL POSITION. y? changes, which are probably exceedingly slow in their progress, may have been repeated at periods of time very far removed from one another. The impregnation with gold of the rocks of the Ural has. been shown by Murchison to have taken place at a comparatively recent date, but in many of the other important gold regions we have not sufficient data to enable us to fix, with any degree of exactitude, the epoch at which the concentration of this metal into veins took place. In California, however, this could not have been effected prior to the deposition of the Jurassic strata in which they occur, A further evidence of the occasional recent formation of quartz veins is derived from the fact, that in one of the detrital beds near Volcano, in Amador County, a distinctly marked quartz vein is observed to cut through the beds of sand and gravel, and presents unmistakeable evidence of having been formed subsequently to their deposition, by the action of water holding silica in solution. This vein is chiefly composed of calcedony and agate, but portions of it are more or less stained by a ferruginous deposit. This is by no means a solitary case, many other localities having been noticed, where quartz veins, almost identical in their general features with those met with in the auriferous slates, must have been formed during the most recent geological epochs.* Auriferous veins, like all others, vary exceedingly, in not only their dimensions, but also in their productiveness. It is, however, generally observed that the widest veins are not usually the richest, and that some of the laminz running parallel with the enclosing walls are uniformly more productive than others. It therefore not untrequently happens that a portion of a vein, sufficiently rich to enable it to be treated with advantage, is separated from another band, comparatively barren, by a distinct heading, or false wall. As a general rule those veins are most productive which afford considerable quantities of disseminated sulphides; although, near the surface, these have, in almost every instance, become decomposed, thereby liberating the enclosed granular gold, and staining the quartz of a brown or reddish colour. When gold occurs in a vein of hard white quartz. without sulphides, it is in most instances found in flakes and granules of considerable size, and is consequently visible to the naked eye; but such veins, although sometimes affording fine cabinet specimens, are not often regularly and remuneratively productive. Some of the most * Geological Survey of California, p, 276. 8 ‘ GOLD. steadily remunerative veins, on the other hand, are only of moderate size, and seldom exhibit visible gold, and this is particularly noticeable in those which, like the Norambagua lead in Grass Valley, California, are divided by numerous thin seams of slate into bands of various thickness. In such veins the gold is commonly in a finely divided state, and principally occurs in the parallel headings, marking the lines of deposition of the quartz. It was formerly believed that veins of auriferous quartz become gradually less productive as greater depths from the surface are attained, but more extensive experience would tend to show that this is in reality not the case. Gold mines which have for many years been continuously worked in various part of the world, have fluctuated considerably in their richness at different depths, but it has not been found that these variations in any way correspond with a gradual impoverishment in the deeper levels. In a communication addressed to Sir R. Murchison, who inclines to the opinion that gold-bearing veins generally diminish in value as they descend in depth, Mr. Selwyn remarks as follows: “There is undoubtedly good evidence that those upper portions of the quartz veins, which have been naturally removed by denudation, and now form the gold drifts, were often far richer than any we now find at the surface; but in drawing conclusions from this evidence, we should not forget that in all probability many hundreds of vertical feet of quartz veins have been thus naturally broken up, crushed and washed, and the fact of the veins, so abraded, being still frequently very rich on their present surface, goes far, I think, to prove that the diminution of yield in depth, even though admitted to be true, on a large scale, is still so slow as not to be appreciable within any depth to which ordinary mining operations are carried.” * Mr, Selwyn con- cludes by expressing an opinion, “that the extraction of gold from quartz reefs, if properly conducted, may be regarded as an occupation, which will prove as permanently profitable in Victoria, as tin and copper mining have been in Great Britain.” | In California, the early quartz miners were also fully impressed with the idea that the outcrops of the leads were more productive of gold than the deeper portions of the same veins, and as soon as the quartz extracted ceased to afford remunerative returns, they usually suspended operations, without extending their explorations to any considerable depth. Within the last few years, however, their opinions in this respect have become materially changed, since the * Siluria, p. 496. GEOLOGICAL POSITION. Q workings of the deeper mines would lead to the conclusion, that, although leads of gold-bearing quartz, like all other metalliferous veins, vary materially in their yield in different portions of their extent, both in length and depth, there is no evidence to indicate a progressive falling off in their yield in the deeper workings. The North Star, Allison Ranch, and Eureka veins, in Grass Valley, will, among many others that might be selected, serve to illustrate the fact, that the Californian mines do not become sensibly impoverished in depth, as, in common with all the mines of this district, they are at the present time quite as productive as they have ever been at any period since the commencement of operations. The North Star vein is now worked on its inclination to a depth of 750 feet, and affords quartz yielding, on an average, gold of the value of 7/. per ton of 2,000 Ibs. whereas in the upper levels the gross value of the gold extracted did not exceed 4/. per ton.* The Allison Ranch Mine has now reached the depth of 500 feet from the surface, and, during the first three months of 1866, yielded a net profit of above 20,0001. The Eureka Mine is being sunk to the 400 ft. level, and produces quartz at this depth fully equal to the average of that raised during any former period, having during the last year yielded 12,200 tons of vein-stuff, affording an average of above 9/. 12s. per ton. Hay- ward’s Mine, in Amador County, is another still more striking instance of the produce of a vein of quartz not decreasing as it goes down. This ledge is worked on its inclination to a depth of above 1,250 feet, and yields quartz of much greater value than that obtained from the same vein at shallower levels. On taking into consideration the whole of the circumstances of the case, it is by no means remarkable that at first the opinion should have become prevalent that quartz veins in most instances become im- poverished in depth. “It will be readily admitted that metalliferous veins are exceedingly variable in their yield at different depths, and it may be supposed that those only which showed evidences at the surface of being more or less auriferous would be at first operated on. These, after having been worked to a greater or less depth, will, in accordance with the general law, begin to show signs of having become less auriferous ; and although a further prosecution of the operations would probably * The ton of 2,000 lbs. is the standard of weight almost universally adopted in the United States of America. : 10 GOLD. have led to fresh discoveries, the miners, in a country where capital is not readily obtained, and where wages are high, become dis- couraged, and finally transfer their operations to other outcrops, presenting a sufficient amount of gold to render its extraction profitable. Another reason for the former prevalence of this im- pression may be traced to the fact, that gold is almost universally associated with a greater or less amount of iron pyrites and other sulphides, and these, becoming oxidised at shallow depths, liberate the enclosed gold, which is thus readily collected by amalgamation, although the deeper, and consequently less decomposed portions of the vein, which may in reality have been equally auriferous, afforded to the early miners less satisfactory results. With the improved methods of treatment, however, which have now come into general operation, this difficulty has to a great extent disappeared, and as all the auriferous sulphides are being at the present time carefully collected for subsequent elaboration, the average production of a vein has generally been found to be sustained at all depths to which the miner has hitherto penetrated.* * The moulds of cubical crystals of iron pyrites are frequently found in the quartz of auriferous veins, and more particularly so near the surface, thus showing that the formation of the pyrites must have been as old as that of the vein itself. In such cases, although the iron has often been entirely removed by chemical action, the cavities left sometimes contain finely divided gold, obviously liberated by the decomposition of pyrites. The gold contained in crystallised pyrites enclosed in quartz, is readily rendered apparent by placing the specimen, for a few hours, in a warm place, in nitric acid, by which the pyrites is dissolved, and finely powdered, or filiform, gold will partially occupy the resulting cavities. With regard to the age of auriferous quartz veins, it has been already shown that many of them must evidently be of comparatively recent date, but in some cases the deposition of gold- bearing quartz would appear to be taking place even at the present time. At Steamboat Springs, near Virginia, in the State of Nevada, and in other localities on the Pacific coast, numerous parallel deposits of quartz, assuming the form of veins, are taking place along a line of boiling springs now in a state of great activity. The quartz from this locality exactly resembles that of the ordinary auriferous quartz veins of California, and besides small quantities of iron and copper pyrites, : contains oxide of iron and traces of manganese. On making an examination of this quartz for gold and silver, we were unable to find an appreciable quantity of either of these metals; but Mr. Laur, who made a similar investigation of this quartz, succeeded in finding specimens containing small quantities of gold. (Annales des Mines, Sixiéme Série, p. 421.) These facts would, therefore, not only tend to lead to the conclusion that auriferous veins are under certain conditions deposited from silicious solutions, but also to explain the action by which many of the slates of the auriferous period may have become metamorphosed and silicified. We are indebted to Dr. Oxland, formerly manager cf the Works belonging to the GEOLOGICAL POSITION, 11 In addition to the gold occurring in veins, considerable quantities are sometimes found forming an integral component of the rocks themselves, as in the syenites of Bogoslofsk in the Ural, and some of the schists in Siberia, &c.* M. Laurf has also discovered the Borax Lake Company, Lake County, California, for .the following note on the occurrence of gold and silver in that locality :— “Jn the Sulphur Bank at Borax Lake, sulphur is constantly in course of forma- tion, with the evolution of aqueous vapour, carbonic acid, and boracic acid, but without any sulphuretted hydrogen, which might have been expected to be present. The smell of carbonic acid is remarkably pungent. The gaseous matters issuing from the Soffioni in gentle blowers are usually at the temperature of about 95° Fahr. They appear to be the agency by which gold, silver, mercury, and iron are brought up from below and deposited in cavities near the surface. Sulphur is deposited on the sides of the cavities, either in groups of crystals, or in highly translucent amorphous masses of a beautiful light lemon-yellow colour. Sometimes the sulphur is intermixed with cinnabar, but more frequently with very fine crystals of iron pyrites, and with pulverulent silica in masses blackened by some hydro-carbon which is difficult to isolate. The iron pyrites may be separated by dissolving off the sulphur with bisulphide of carbon, and washing off the silica with water. It is found associated with silver and a trace of gold. “On the sides of the cavities of the blowers, gelatinous silica is sometimes found coating opalised silica in varying degrees of induration, according to its depth from the surface, presenting examples of opal or hydrated silica in its various stages of formation, from gelatinous silica up to the hardest opal. The indurated silica is sometimes colourless, but is more frequently permeated with cinnabar or iron pyrites, and blackened by the tarry matter before alluded to. Sometimes from a diffusion of cinnabar throughout the mass, in minute quantity, it is delicately tinted of a pinkish colour, The cinnabar is also found in striz, and occasionally even in veins and concretionary masses of some thickness. Where the bituminous matter occurs in the largest quantity, and the mass is quite black and friable, cinnabar is replaced by metallic mercury. “Tn another locality of similar character, about ten miles distant, gold has been found with cinnabar in crystalline masses of some size. In the same place, a vein of apparently compact quartz, about ten inches in thickness, was found to be so friable that it could be easily taken out with the hand in smail conchoidal fragments, most of which rapidly fell into fine powder. From its great resemblance to a vein occur- ring in the Mexican Mine, Virginia City, which is many feet in thickness, and con- tains $20 to $30 of gold and silver to the ton, attention was drawn to it, and it proved, on being assayed, to contain silver, with a trace of gold, to the value of $15 per ton. “These phenomena present indubitable evidences of the volatility of gold, silver, mercury, and iron, in presence of aqueous vapour associated with sulphuretted hydrogen, carbonic acid, and boracic acid. Whether the contemporaneous associa- tion of these substances may produce a definite compound possessing peculiar powers of solution and volatilization under the influence of elevated temperature, although probable, yet remains to be proved.” * Siluria, p. 481. t Annales des Mines, Sixiéme Série, p. 434, sie GOLD. presence of gold in the metamorphic shales of Mariposa County, California ; and similar deposits, containing a considerable amount of the precious metal, are known to occur near Lincoln in that State. It is not, however, from the treatment of auriferous quartz that the principal portion of the gold of commerce is procured, a very large proportion of it, probably more than two-thirds, being obtained from alluvial diggings, in which the gold is separated from the more or less superficial detritus by washing. In some of these deposits nature has been for ages performing the operations of crushing and concentrating on a vast scale, and has deposited the precious metal in positions from which it can be obtained without a large expenditure of either labour or capital. To this circumstance are attributable the great variations which are observable in the pro- duction of gold throughout the world; since, on the discovery of new and extensive alluvial diggings, an almost unlimited supply of unskilled labour can at once be applied to its extraction, whilst the same weight of metal, if retaining its original position, could only be collected by the application of a large amount of capital and skilled labour. Indeed, experience clearly shows, that had not this natural concentration taken place, the larger proportion of the gold annually brought into the market could not have been profitably collected, since, in the majority of cases, the veins, from which it must have been originally derived, are not sufficiently rich to defray the expenses of raising and crushing. It does not seem to admit of a doubt that these deposits have been principally derived from the degradation or breaking up of auriferous veins, and the distribution of the detritus thus formed, chiefly by the agency of running water. It further appears to be conclusively proved, that this gold-bearing drift is, at least, of two distinct geological epochs, both comparatively modern, although the latter period is distinctly separated from the earlier, and its materials chiefly derived from the disintegration and redistribution of the older placers. In California these appear to be distinctly referable to a river-system different from that which now exists, flowing at a higher level, or over a less elevated continental mass, but sometimes in the direction of the main valleys of the present period. The sources to which the chief annual supply of gold is referable are, therefore, the following :— GEOLOGICAL. POSITION, 13 Ist. Auriferous veins, most frequently enclosed in metamorphic slates. 2nd. The distribution of placer gold .by ancient river-systems, known as Deep diggings. 3rd. The distribution of placer gold by the present river-system, giving rise to the Shallow diggings. The separation of gold from its original matrix, and its concentra- tion and deposition among and beneath strata of gravel, sand and clay, are the result of causes acting through immense periods of time, and which, although they have not yet ceased, are probably much less energetic than they were at a former but not very remote, geological epoch. The strata constituting the earth’s crust are con- stantly undergoing abrasion and decomposition from various meteoro- logical causes, of which one of the most active and powerful is the alternate freezing and thawing of water retained in the fissures and erevices of stratified rocks, which tend to disintegrate and wear away the more elevated and exposed portions, and to carry down the abraded and loosened fragments and spread them out over the surface of the country at lower levels. On the declivities of lofty and rugged mountain chains, where torrents, either from the fall of rain or the rapid melting of the snows, are of frequent occurrence, the streams, become suddenly swollen, rush with violence down their flanks into the valleys beneath, and thus develop a force capable of rapidly eroding the rocks over which they pass. In addition to this mechan- ical force, chemical action frequently lends its aid to effect the disintegration of auriferous rocks. In proportion as the gold-bearing strata are worn away, the sulphides with which they are constantly associated become oxidised, and, being thus disintegrated, the rocks are themselves reduced to fragments, which being carried by the action of water into the valleys, the metallic particles, as the heaviest, are first deposited, and sink to the bottom, whilst the lighter earthy and silicious portions are removed by the current to a greater distance. Geologists are not yet agreed with regard to the identity in origin of the older auriferous sands and gravels, and the modern alluvial formations affording gold: Sir R. Murchison, in particular, strongly insisting that the more or less superficial deposits, constituting the deep diggings, are in no way to be confounded with the modern drifts resulting from present atmospheric causes, but rather that they are the result of diluvial currents closely connected with great 14 GOLD. physical changes in the earth’s surface, such as the elevation of some of the principal mountain chains, &c. The vast accumulation of this débris, in some of the mining districts of California and Siberia, would indeed lead to the conclusion that the forces at present in operation were totally inadequate to produce such stupendous results ; but until a much more thorough examination shall have been made of some of the great gold-producing districts, it would be injudicious to attempt to arrive at any definite conclusion on this subject. Baron Richthofen is, however, at the present time engaged in an examination of the deep placers and ancient river-courses of California, and there can be no doubt but that a large amount of additional information on this subject will be derived from the investigations of this indefatigable explorér and able geologist. CHAPTER IT. GOLD REGIONS OF THE OLD WORLD. GREAT BRITAIN AND IRELAND—FRANCE—SPAIN AND PORTUGAL—ITALY—SWITZER- LAND— HOLLAND — RUSSIAN POSSESSIONS—-GERMANY— AUSTRIAN EMPIRE— CENTRAL AND SOUTHERN ASIA—CHINA AND JAPAN—AFRICA, HAvInG made certain general observations on the occurrence of gold, we will now proceed to a consideration of some of the. principal auriferous districts of the world. GREAT BRITAIN AND IRELAND.—Cornwall and Devon.—The tin streams of Cornwall have been long known to afford occasional speci- mens of gold, but not in sufficient quantities to make its collection a matter of any commercial importance. Carew says—“Tynners doe also find little hoppes of gold amongst their Owre, which they keepe in quils and sell to the Goldsmithes, oftentimes with little better gaine than Glaucus exchange.” * Pryce mentions a piece of gold, found in Cornwall, weighing 15 dwt. 16 gr.t Many of the copper gossans are also known to contain minute quantities of gold, but we are not aware that it has, in any instance, been extracted with advantage. At the Britannia and Poltimore mines, near North Molton, in Devonshire, gold has also been found in small quantities, but it never paid the cost of extraction. Wales—In North Wales, especially in Merionethshire, the older slaty rocks have long been known to be more or less auriferous. The gold-bearing district of this country would appear to be chiefly confined to an area of about twenty-five square miles, principally lying on the north of the turnpike road leading from Dolgelly to Barmouth. In this region the Cambrian rocks are overlaid by the Silurian, and the general geological features of the country strongly resemble those of some other auriferous localities, Among the veins which have attracted the most attention are those of the Dol-y- * Carew’s Survey of Cornwall, 1602, book i. + Pryce’s Mineralogia Cornubiensis, p. 52. 16 GOLD. frwynog, Prince of Wales, and Vigra and Clogau mines, of which the latter only is understood to have been ever worked with remunerative results. So long ago as 1844, a paper was read before the British Association by Mr. Arthur Dean, who stated that a complete system of auriferous veins existed throughout the whole of the Snowdonian or Lower Silurian formation of North Wales. In consequence of this statement operations were commenced at Cwn Eisen, but the results obtained not having been found satisfactory, they were finally aban- doned. Machinery for crushing and amalgamation was, about two years afterwards, erected at Dol-y-frwynog, but after operating on several hundred tons of quartz, the result was in this instance also a failure. Of all the auriferous veins that have been worked in the neighbourhood of Dolgelly, that of the Vigra and Clogau has certainly been the most productive. This mine is situated at a height of about a thousand feet above the level of the sea, the workings being pro- secuted on what is called the St; David’s or Gold Lode. This lode, which is almost vertical, runs nearly east and west, and is composed ~ of quartz, more or less impregnated with sulphides of iron, lead, and copper. The veinstone also, at one period, particularly during the year 1862, exhibited for a short distance a considerable amount of dis- seminated gold, This rich deposit is at present reported to have been entirely worked out; but for a considerable time rather large amounts of gold were returned from the property. The following table, for which we are indebted to Mr, R. Hunt, keeper of Mining Records, shows the returns made by the various Welsh gold mines from 1860 to 1864, or during the time of their largest yield :— perp PRODUCED IN pea es ES = z : ae | | | 1861. 1862, | 1863. 1864, Gold. | Value. | Gold. | Value Gold. | Value. | Gold. | Value. OZ. £& OZ. £ OZ. ££ OZ. £ —-—-— >, | —_ -—_ Vigra and Clogau . | 2,886 | 10,816) 5,299 | 20,390} 526 | 1,674 | 2,331 | 3,434 Gea Coe Pith — — — — 25 a3 346 | 970 | Castell Carn Dochan — — —— — == — 141 394 Prince of Wales. — —_ — ET ee = is 63 | 166 Gwyn-fynydd — — _- ~— — — 6 17 ta - <> The number of tons of quartz crushed in Wales during the year 1865 is returned as having been 4,270, yielding 1,664 oz. of gold, or about 0.39 oz. per ton. The total quantities of gold raised from the commencement of GOLD REGIONS OF THE OLD WORLD. ay operations in the North Wales Gold District, up to April 1st, 1866, are estimated as follows :— Gold obtained. Oz. Gia Dalyirwyn0e. sn se es 117 UCR TeV RIES S c/o Seta rec + 63 PE ESASETRGE Gy 176 PyvNVGd. . 6 Prem oc sere pte me ON ee 478 Castell Carn Dochan». . 9... . 2 182 Wipe and Clogatesn. i) wou bcs). 201,778 Total eovec eye ee 12,800 As above stated, the productive portion of the Vigra and Clogau lode appears to have become exhausted, and although expensive and efficient machinery has been erected on a large scale, with a view to the treat- ment of the average quality of quartz produced from the vein, the results hitherto obtained have been far from satisfactory ; and, unless some marked improvement should ere long take place, it is to be feared that the Vigra and Clogau may ultimately add another to the list of Welsh gold mines that have absorbed a much larger amount of this metal than they have ever produced.* The old Dol-y-frwynog was reworked for gold in 1864, but without any commercial success, since the average yield of the quartz obtained was only about 26 grains per ton. Scotland.—Gold has also been found at Lead Hills in Scotland, several hundred men having been employed there in washing gold sands during the reign of James V. Pennant says—“In the relen of James IV. the Scots did separate gold from the sand by washing. In the following the Germans found gold there which afforded the king great sums; three hundred men were employed for several summers and about 100,0002 sterling procured.” + Ireland.——In the county of Wicklow, a considerable amount of excitement was caused, in 1796, by the discovery of gold in the débris of the valley, at the base of Croghan-Kinshela. These diggings were carried on for about two years, when the works were destroyed by the Irish rebels; but although a considerable quantity of gold was extracted, one specimen in particular weighing no less than twenty-two ounces, the general results obtained do not appear to have been very satisfactory. In 1801 the operations were resumed * Some further discoveries of gold at Vigra and Clogau have been recently announced. + Pennant’s Scotland, vol. ii. p. 130, LZ 1&8 GOLD. with a view of discovering the gold-bearing veins; but after the expenditure of large sums, without success, in various mining opera- tions, the locality was again abandoned. FRANCE possesses no known valuable gold mines, but the sands of some of her rivers are, to a certain extent, auriferous. The only quartz vein which has been found to contain gold, is that of La Gardette in the Department of the Istre, which is from two to three feet in width, and enclosed in gneiss. Gold was discovered in this locality in 1700, and workings were intermittently carried on, up to 1841, but the quantity obtained was exceedingly small. The Rhine has, for centuries, produced small quantities of gold, and, according to the report of Réaumur, presented to the Academy of Sciences in 1718, its sands have been chiefly worked between Strasburg and Philipsburg. Near Strasburg it was formerly the perquisite of the magistrates of that city, who farmed out the right of gold washing, but in the year above referred to they only received some four or five ounces as their pro- portion of the annual produce. In 1846, M. Daubrée, a French engineer, made a report to the Academy of Sciences, in which he states that the gravel most usually worked is that deposited below a sandbank or gravel island, which has become eroded by the river, and that gold is only found in any degree concentrated in the coarser. gravels, which have been freed from the finer sands by the action of currents.* The gold occurs in the form of small scales or dust, and is constantly accompanied by titaniferous iron, the amount of which is proportionate to the richness of the sand for the precious metal. The workable beds are invariably thin, seldom exceeding from four to six Inches in thickness, and the particles of gold remarkably small, since the number required to weigh one milligramme varies from seventeen to twenty-two, and one cubic metre of gravel contains from 4,500 to 36,000 of these scales. Besides the auriferous deposits in the bed of the stream, M. Daubrée states that the ancient detritus on its banks, extending from three to four miles in width, also affords an appreciable amount of gold, but that the fine silt, free from gravel, which is daily accumulating, is totally barren. The sands of the Rhine are still washed on a small scale, but there is reason to believe that the production was formerly much more con- siderable than at present. The yield of the year 1846 is estimated by M. Daubrée at 1,800/. and the washers usually made from one and * Comptes Rendus, xxii. p. 639, 1846. GOLD REGIONS OF THE OLD WORLD. 19 a half to two franes per diem, although they occasionally gained from ten to fifteen francs. The same authority estimates the average yield of the sands of the Rhine, Siberia, and Chili to be in the proportion of 1:20 : 74; or, if the sand of the Rhine, separated from pebbles of two-thirds of an inch in diameter, be taken as the standard of com- parison, the ratio becomes 1:10 : 37. In Siberia, sands containing 0000001 of gold were then not considered worth working; but even this yield is seven and a half times greater than that of the ordinary sands of the Rhine. M. Daubrée, after a careful examination of the subject, came to the conclusion that by the aid of proper appliances these sands might probably be treated advantagéously, and goes on to say, that, “by the processes now employed, each washer gains from one and half to two franes a day, and exceptionally even ten or fifteen francs; some of the operations would, however, appear to be susceptible of improvement, since the washing is now entirely effected by manual labour, although there is to be obtained, at the distance of a few steps only, the motive power of the river itself, which, if applied to a dredging machine, could be made to remove the super- ficial stratum of rich gravel, and deposit it on the head of a washing table.” Although, however, the application of machinery might be made to materially lessen the expense of working the deposits of the Rhine, the yield of gold is so exceedingly small, that it is question- able whether, by any known mode of treatment, such results could be obtained, as would afford satisfactory returns for thé capital and labour which would be required. There are several other localities in France which have afforded small quantities of gold, and the River Ari¢ge (Aurigera) is stated to have derived its name from the amount of auriferous sands it deposited. The washing of these is said to have afforded, up to the close of the fifteenth century, an ‘annual produce of about a hundred pounds of the precious metal. Small quantities of gold have also been collected by washing the débris produced by the erosion of some of the lower carboniferous strata in the Department of the Gard, and we have ourselves found traces of gold in the quartzose pebbles, forming one of the con- stituents of a coarse conglomerate, a little above the village of Bessage. SPAIN AND PorTUGAL.—Gold mines were successively worked in Spain by the Pheenicians, Romans, and Moors; and although the amount | C2 20 GOLD. at present obtained from that country is exceedingly insignificant, it at one period produced large quantities of the precious metal. Both Strabo and Pliny speak of Spain as being rich in gold, and mention various localities from which it was obtained. Adrien Paillette, who has investigated the subject of ancient mining in the Peninsula, has arrived at the conclusion, that in former times, both Spain and Portugal yielded large quantities of gold, which was not only obtained from washing the sands of the Duero, Tagus, and some other rivers, but also from workings in the solid rock. It would appear, however, from the investigations of Paillette, that however rich the auriferous regions might have originally been, they had become almost totally exhausted previous to their abandonment; since during the whole of his investigations of the old workings, which are very extensive, he only obtained a few slight traces of gold. Among the gold mines of the Peninsula which have been in operation within more modern times, may be mentioned one near Talavera, worked by Donna Isabella: * another at Adissa, near S. Ubes in Portugal, was worked during the present century, and which produced as much as forty-one pounds weight of gold in 1815.+ A mine at Domingo Flores in Leon was worked intermittently from 1639 to 1749. The present production of the precious metal in Spain is exceed- ingly small, and is chiefly derived from washing the sands of the rivers Sil and Salor, from which the total annual yield may be estimated at about 1,600. Iraty.—A great number of localities in this country were known to the ancients as producing gold. The whole district of the Noric Alps (Illyria) was considered highly auriferous, and at one period gold was worked so extensively, that the large quantity produced is said to have caused a reduction of one-third in its price throughout Italy.t Gold was also found in Dalmatia,§ the River Po,|| and at Pithecusa, . opposite Cuma. - The only gold mines at present of any consequence are situated in Savoy and Piedmont. The chief amalgamation works are built on the small streams near Macugnaga, at the foot of Monte Rosa, where a considerable amount of gold is found in the valleys of Anzasca, Toppa, and Antrona, and to a less extent in those of Alagna, * Jacob’s History of the Precious Metals, vol. ‘ Dp. 222: Tt ibid: p. 283. £ Strabo, lib. iv. cap. 6. § Phin. Hist. Nat. xxxiii. 21. | Ibid. | Strabo. GOLD REGIONS OF THE OLD WORLD. 21 Sesia, and Novara. The chief mines in Anzasca are at Peschiera and Minera di Sotto. | The ore is an auriferous pyrites, containing on an average about 12 dwt. of gold per ton. The whole amount produced in the province of Ossola, to which these works belong, was in 1829 about 250 lbs. troy, with a profit of a little over 3,0002* In 1844 the yield was as follows :t— Kilos. Value. Meey/ Or Anzascat ey wid ee 9158 £16,092 . LS eS) Aa) SP ae ee eS 4 Se 2,032 A ADEM te ei tana 6+ OU 2,150 PobaLS conus is! 20,274 The yield of Alagna, Sesia, and Novara during the same year only amounted to 280/. Pliny states that these mines were extensively worked in his time, and that the number of slaves who were allowed to work in them was fixed by the Senate at 5,000, in order to prevent a serious reduction in the price of the precious metal, Several of the mines in this district have recently been undertaken by English companies; but these have not as yet been sufficiently long in operation, to allow of a satisfactory estimate being made relative to the probable returns of gold, although the results hitherto obtained have been of a very encouraging character, SWITZERLAND produces no amount of gold of any commercial im- portance ; but the sands of the rivers Reuss and Aar, two of the affluents of the Rhine, are known to contain small quantities of this metal.t The Rhine in the Pays de Gex is shghtly auriferous, and the Tessin, or Ticino, in the Canton of the same name, deposits sands sometimes affording small particles of gold. HOonLanD.—Some operations were carried on in this country in the eighteenth century by a Mr. Beecher, with a view to the eXx- traction of gold from the sea sands, but he did not succeed in his enterprise, and a previous adventurer is said to have been equally unsuccessful. Russian Possessions.— The principal portion of the gold from the * Whitney’s Metallic Wealth, p. 96. + Mining Journal, 1845, p. 610. + Dictionnaire des-Sciences Naturelles—Or, 22 GOLD. Russian Empire is obtained from the western slope of the Ural Mountains, Siberia, and the Caucasus. The government of Arehangel also formerly furnished a smal] quantity of this metal, but the works in that district have been abandoned since the commencement of the present century. In Asiatic Russia, the most productive auriferous districts are comprised within the governments of Perm, Tomsk, Oremburg, Irkoutsk, Yenisseisk, and the district of the Kirghese. The first discovery of gold was made in the year 1743, near Ekatherin- burg, and in 1752 the first mining operations were commenced at Berezovsk. These mines, which are sunk in the solid rock, still continue to be productive, although their yield is at present much smaller than it was formerly. In the year 1823 there were no kss than sixty-six localities in the Ural from which gold had been obtained by deep mining, but the whole of these undertakings, with the exception of eight, had at that time been abandoned. The auriferous veins of the Berezovsk mine are numerous, but generally small, and occur in a sort of decomposed granite, which itself forms veins and dykes in talcose, chloritic, and micaceous shales. The most productive veins are of quartz, cutting the granite nearly at right angles, and having an almost perpendicular dip. These veins seldom extend beyond the granite, and appear to become less productive in depth. Towards the close of the last century, the Berezovsk Mine yielded from 600 to 800 lbs. of gold annually, but the production has of late years much decreased, and in 1850 the total yield had been reduced to 100 lbs. troy. During the most - prosperous period of their exploitation, the stamped work from these mines afforded from 6 to 11 dwt. of gold per ton. The gold washings proper of the Ural, which have produced such a large amount of the precious metal, and which, before the discovery of the deposits of California and Australia, had acquired so much celebrity for their richness, were commenced by the Russian Government in 1814, whilst those of Western Siberia were not opened until 1829, and those of Eastern Siberia remained unworked until 1838. The method of occurrence of gold in some of the more important of the Russian alluvial diggings will be understood from a description of the Soimanofsk Mines, north of Miask. Here, creat masses of ancient drift or gravel having been removed for the extraction of gold, the eroded edges of highly inclined crystalline limestone have been exposed, which, from being near the centre of the chain, are believed to be of Silurian age. It is from the GOLD REGIONS OF THE OLD WORLD. 2a adjacent eruptive serpentinous masses and slaty rocks, }, Fig. 1, that the auriferous shingle ¢, usually more productive near the surface of the abraded rock a, has been derived. Bt (7 eye, t Uf ip i uy y} Tins 2) biel Y a Dieaines at THE SoimMANOFSK MInzEs. (From “ Russia and the Ural Mountains,” vol. i. p. 487.) The tops of the highly inclined beds a are rounded off, and the interstices between them worn into holes and cavities manifestly by very powerful aqueous action. Here, as at Berezovsk, mammoth remains are found lodged in the lowest part of the excavation, at the spot towards which the small figure of a man is pointing, and at a depth of about 50 feet below the original surface of the overlying coarse gravel c, before its removal during the progress of the operations. The feeble influence of the existing stream in ex- vavating even the loose shingle, is seen at 0, the bed of the rivulet having been lowered by artificial means from its natural level 0, to that marked , for the convenience of working the deposit. In some spots the gold-bearing alluvium is a heavy clay, whilst in others it is made up of fragments of quartz veins, chloritic and talcose shales, and greenstone, which lie on the side of the hillocks of eruptive rock. _ It was from one of these gravelly depressions, south of Miask, that the large lump of solid gold was found, which is now preserved in the Imperial School of Mines at St. Petersburg, and which weighs ninety-seven pounds troy.* _ The auriferous detritus of the Ural Mountains is, however, poor in comparison with the deposits which have since been found in California and Australia; for although very large nuggets have occa- sionally been met with, much of the auriferous ground, which in the * Siluria, p. 484. 24 Comp. Russian Empire, where labour is cheap and water-power abundant, can be worked at a profit, would, if in California or Australia, be neglected as being of no practical value. | The following table shows the production of the Russian woskiage from their commencement to the year 1860 : *— Lbs. Troy. 1814 to 1820 Produce of the Crown washings . . . . 11,085 1820 to 1830 Crown and private... 2 1830 to 1840 ___,, : a cw a Ee a 1840 t0 1850.2 ° SS , Oca ca o ame 3 a eo) SS 2 7S S z £ 3 a . pees i HH Wh7 = S Ziyi \ SS g \\ ie i, ae if ‘ S WES E i : fen ae z = g wi Ye Z| WWE: Mie \ iia “ 1 \\\ i) UY Dx uN Ze aS UN Ns 2 4 WM : = : 4 WWLZA : | WA OZ Bali aas ha) “a AWG wit CRUZ Hy iN / Gyypy. Uy) Hi WWW SS Se & a \ ory XX i NOTE. Zhe Geld Vans ‘shewr thus —_.......-- Seale of Map 20 Chains — One Inch. Newheryd: Alexander, Lith 43, Castle S¢ Holborn, | —— ene eS E.& FN. Spon.46, Charing Gross.London. UNITED STATES OF AMERICA. 63 able for the large number of trunks of trees buried in the detritus. These are silicified, and bear evidence of having been subjected to the action of powerful currents, before being deposited in the position in which they are now found. The most important hydraulic washings in this county, at the present time, are those extending along its north-western border, parallel to, and in the vicinity of, the bed of the Middle Yuba. ; Sierra County is bounded on the south by the Middle Yuba, whilst its northern boundary is formed by the irregularly curved water-shed between the Feather River and North Yuba; east and west it extends from the State line to Yuba County. The western, or principal mining portion of this county covers an area of about twenty-five Square miles. Some of the principal quartz mines are situated four- teen miles above Downieville, within 1,500 feet of the summit of the Buttes, and probably about 7,000 feet above the level ‘of the sea. The Sierra Buttes Mining Company.—The mine and mills belonging to this Com- pany are situated at an elevation of 2,000 feet above the bed of the river, near the outcrop of an immense vein called the Cliff Ledge, which can be traced for a great distance across the ravines by which the country is intersected. The bearing of this ledge is nearly east and west, with a dip of 42° towards the north. It varies from six to thirty feet in width, and is enclosed in a hard metamorphic rock. That portion only of the lode which is found near the foot wall, and which varies from two to— seventeen feet in thickness, is passed through the mill, the remainder of the ledge not being considered sufficiently auriferous to pay the expenses of treatment. This Company has two mills of twelve stamps each, worked by water powcr, one of them having been built in 1853, and the other in 1856. These mills are capable of working monthly, 900 tons of quartz, of which the yield in 1860-1, averaged $14.82 per ton. The cost of raising the quartz, and delivering it at the mill, is stated to be $5.87, and the expense of crushing and amalgamating $1.35 per ton. This mine was first taken up in 1851, and worked by arrastres until 1856, when it was purchased by the present owners, who commenced working it in the spring of 1857, with one Chilian mill, and five arrastres, and have obtained the following annual results :— | } Taken from Mine. , Expenses, Dividends. , BT NS Re) 5002) B51000 $15,000 $36,000 PPP Gi). Mote...” 55,000 15,000 40,000 SB i 5. “88,000 20,000. 68,000 OU er... ~,, - 120,000 37,000 83,000 Beet th. P=! 198,000 48,000 150,000 BeGsen EL 2 “4 (186,000 54,000 112,000 ERG tus?) aT 5 LBG,000 SOE OT OOO 99,000 1864. . . . , 90,000 dss 7TD.OO0 x - 15,000 eee. Ss ,. .” 196,000 . 64,000 132,000 $1,120,000 - $385,000. $735,000 v4 COLD, The foregoing item of “expenses” includes all improvements, from taking posses= sion of the mine, up to the present time. No calls were ever made, and therefore the whole outlay for machinery has come out of profits realised. In the fall of 1858, the first stamping mill was erected, to which a second was subsequently added. The smallness of the return for 1864, was the result of a deficiency of water, caused by the great drought of that year, and consequently, in order to avoid the recurrence of similar interruptions, an aqueduct was, in 1864, brought in at an expense of $40,000. In addition to the vein, from which the principal part of the gold produced has been derived, there is on the property, another parallel ledge, called the Aérial, from which some good quartz has been crushed. _ The Independence Mine is also on the same veins, and produces quartz having nearly a similar tenure in gold, ae! A great many other important quartz mines have been opened, and are in full operation in this neighbourhood, but we are without par- ticulars relative to their yield or situation. The.most important feature of this county is the Plue Lead, one of the many ancient river channels found in various localities in the mining regions. The characteristics of this old river bed do not materially differ from those of the auriferous deposits found under Table Mountain, in Tuolumne County, except that in Tuolumne the course of the ancient currents by which the detritus was deposited, was nearly coincident with that of the streams flowing through the district at the present day, whereas in Sierra County the direction of the Blue Lead is nearly at right angles to that of the modern rivers. As a consequence of this difference of direction, its continuity has been frequently interrupted by the erosion caused by the passage through it of the more recent streams. It is also to be observed that the valley of the river under Table Mountain was evidently filled up by one great continuous flow of lava, whilst, in the present instance, the volcanic phenomena are so numerous and complicated, that itis not easy to determine, whether the changes which first turned the course of the ancient river, and subsequently covered, to a great depth, its former bed, were the results of one, or several successive eruptions. Mr. C. 8. Capp observes, relative to the Blue Lead: “Hundreds of tunnels have been run in search of it, Where the line it follows has been adhered to, they have always found it, and have been well rewarded for their labour. Millions of dollars have been taken from this lead, and its richness, even in portions longest worked, is yet undiminished. These tunnels have cost from $20,000 to $100,000 each, and interests in the claims they enter, sell readily at from $1,000 to $20,000; in proportion to the amount of eround within them remaining untouched, and the facilities which exist for UNITED STATES OF AMERICA. 65 working it, many of these claims will yet afford from five to ten or more years’ profitable labour to their owners, before the lead itself within them is exhausted.” * Yura Country les west of Sierra County, and extends to the Sacramento River, one-half lying in the mountains, and the other in the plains, the mining district being principally in the former. The chief mining towns are Camptonville, Timbuctoo, Foster’s Bar, Texas Bar, and Long’s Bar. The Assessor’s report for 1860 mentions only two quartz mills as being at work in this county. Hittell states there are twenty-two ditches in Yuba County, having an ageregate length of 942 miles, giving an average of 43 miles each. The most important of these is the Bovyer Ditch, which supplies Timbuctoo, in winter, with 5,000 inches of water; but this amount somewhat diminishes during the summer months. Borre County lies west of Yuba and Plumas counties, and is drained by the Feather River. Its principal mining towns are Oroville, Bid- well’s Bar, Forbestown, Natches, and Whiterock. In 1860 there were twenty-nine quartz mills in this county. It contains sixty-four mining ditches, having an ageregate length of 583 miles. The most important of these is that belonging to the Cape Claim Company, near Oroville, which has an aqueduct, built in 1857, three-quarters of a mile in length, and twenty feet wide, which furnished employment for 250 men during six months, and cost $176,985. The receipts during the first season amounted to $251,426, showing a profit of $74,441. An extension of this flume was undertaken during the succeeding dry season, but the next year’s receipts were considerably less than the outlay. Pivmas Counry.—This is a large, but not very important mining county, and comprises the whole of the region drained by the Upper Feather River and its affluents. About one-third of its surface is more or less auriferous; but, during the winter months, mining opera- tions are much impeded by ice and snow. The principal mining towns are Quincy, Jamison City, Indian Bar, Nelson’s Point, and Poorman’s Creek. There are five quartz mills in this county, and a considerable amount of gold is obtained by tunnel and hydraulic mining, * Quoted in Hittell’s “ Resources of California,” p. 293. 1 66 GOLD. In addition to the gold annually yielded by the great auriferous region which we have thus endeavoured to describe, a certain amount of the precious metal is also procured from various less important localities, in different parts of the State, but which space will not allow us to particularise. We cannot, however, conclude this portion of the subject without noticing the quartz mines of Kernville and Clear Creek, south of Mariposa, whence some patches of the auriferous zone would appear to extend, southward, to those localities. There are several mills at Kernville making satisfactory returns, whilst there is every probability that Clear Creek, at which there are some six or eight already in profitable operation, will eventually become an active- and prosperous mining centre. , Aaa The gold yield of California reached its culminating point in 1853, and the exportation of treasure, which rose in that year to $57,330,034, gradually fell until 1861, when it was $40,639,080. The silver of Nevada, and the gold of Idaho, then began to flow in, and the amount of the shipments again rose. The following table shows the estimated annual yield of yold, and the annual amount of treasure manifested for exportation, from the commencement of operations in 1848, to 1866, both inclusive :— ee Estimated Amount Amount of Wears Estimated Amount Amount of “| of Gold produced. | Treasure exported. ‘| of Gold produced. | Treasure exported. 1848 $10,000,000 | (no record.) Brot. 1849 40,000,000 $4,921,250 forwd.| $505,000,000 $373,467, 283 1850 50,000,000 27,676,346 1858 50,000,000 47,548,025 1851 55,000,000 42,582,695 1859 50,000,000 47,649, 462 1852 60,000,000 46,588, 434 1860 45,000,000 42,203,345 1853 65,000,000 57,330,034 1861 40,000,000 40,639, 080 1854 60,000,000 51,328,653 1862 34,700,000 44,561,761 1855 55,000,000 45,182,631 1863 30,000,000 46,071,920 1856 55,000,000 48,880,543 1864 26,600,000 55,707,201 1857 55,000,000 48,976,697 1865 28,500,000 44,984,546 Carried | 1866 26,500,000 44,364,393 on $505, 000,000 $373,467, 283 Total | $836,300,000 $785,197,016* About one-third of the gold annually obtained from California is the produce of quartz mining, whilst the remaining two-thirds are. procured from the shallow placers and hydraulic mines. OTHER STATES AND TERRITORIES AFFORDING GoLp,—The gold obtained from the State of Nevada is now chiefly derived from the treatment of the auriferous silver ores of the Great Comstock * This includes about $65,000,000, the produce of Nevada, &c. UNITED STATES OF AMERICA. 67 Vein, in which the gold usually presents about one-third of the total value of the precious metals contained in the rock. The production of gold from this source, since 1861, has been, according to Richthofen, as follows :— Dot ere ng ky 81,500,000 Wie ee es 4,000,000 nn eh. ome Et Pr8G? 25 000,000 Mem mats oe ke) tee Ee res hold, ell 14-4.760,000 Total produce 1862—1865 . . . $15,250,000 In Eastern Oregon, Washington Territory, Idaho, and Montana, large auriferous districts have been recently discovered, every year adding to their extent, in proportion as these hitherto little known regions become more widely explored. Shallow diggings have been worked for nearly ten years near Fort Colville, on the Upper Colum- bia river, and results have been obtained which would have been highly satisfactory, had it not been for the difficulty and expense of obtaining supplies, and the frequent troubles with the Indians. The production of gold from these northern countries has been for several years considerable, and is steadily and rapidly increasing; but the whole amount of the precious metal hitherto received from these regions, has been exclusively obtained from river diggings, and other very shallow sources. It is not, -however, probable that, for a very long period at least, these countries will at all approximate in their yield to the annual pro- duce of California, since there are many things calculated to deter any but the most resolute and hardy, from seeking their fortunes in these wilds. The winters are long and severe, and for six months of the year travelling and the transport of materials and provisions are impossible. To this must be added the frequent hostility of Indians, and the notoriously bad social condition of the white inhabitants ; life being insecure, and property almost without protection. A certain amount of gold is annually produced by the territory of Utah, but the quantity is believed to be small. The same may be said of Arizona, although, judging from the reports of miners and others who have visited these regions, it would appear that the limited nature of the returns is rather a result of the small number of miners, chiefly caused by the hostility of the Apaches, than from any defi- ciency in the richness of the auriferous deposits which have been discovered. ; F2 68 GOLD. The mining districts on the banks of the Lower Colorado continue to possess attractions for a considerable number of miners, who have been at work on them for several years. Hitherto, however, they have produced but a small amount of bullion, but promise to increase in importance, and will, it is generally believed, ultimately supply the market with large quantities of the precious metals, The following tables contain valuable data, obtained from official — sources, relative to the production of gold in the United States :— =P) © UNITED STATES OF AMERICA. EL-€16 ‘G06 0G3S | 16. F98FFS 19.869 ZS S8-861 BS 08-398 ‘989S$ | So. 12193 9.608 ‘L$ 16-988 °ISE‘e3 | LO-IS8‘tI3 66 280'%ES'S | [eIOL | F8.919‘S18‘S “te 88-168 sis IL-00F ‘982 aed +i PL GFL “Car GI. 129 OF £8 983°S12‘T 99ST 18.089 ‘$163 a 18-919 ae GI. £98 ‘00F 'T ed 08-913 66.066 ‘SOE G0. 167 IL TL 0668S § GOST | FO. FST ‘116 'T ns FL F6 as 09. 68L°L68 16. LPE 4 GL-FIL GL- OF L°C86 06-361 'FL di FOST : 1LT-090 ‘940% 4: 89. G0TS 88-861 °3S 16-918‘. $ | 88-€9¢'ST GL.698°S 18-638‘968‘L | 821-016‘ ve S98T | CF. 068 “SEF ‘T 4 ee os — 01-613 § “ 09-888 ‘ZSL‘T ie aa Z98T SF. 28 ‘890'T 96-206 ‘T ae as ase “ LE-840 ES 80-266 ‘109 a as T98T 9Z-O8T‘St0‘T 10-GOF‘T te = i a oe G0. $09 ‘9FS 9T-081°3 #7 09ST 5L- 102 ‘610'T eee see ee eee eee eee 00-SFL g 00-069 '% wee 6S8T | 10. GE ‘SSF ‘T coe eee tee eee oe eee eee 00. 009‘¢ eee SSSI 29-&1F'190'86S | 00-812‘ ee ot oe 7 ain aa 00-83 Fes 2 LE8T 04 SFSL 00- 1¥#9‘Ez9‘Z 00-180 ‘TZ eee eee ove wee ee eee eee eee LEST 0} SEST 00-00°€90"¢ 00-002 ‘1g eee eee ore he eee eee eee eee LEST 04 SZ8L J 00-000 OLT ¢ eee eee eee eee e eee erry eee eee LE8L 0 FUSL . ‘ . OF) K "IVLOL = | ‘SHUN ATHIO) “vVavaaN goer gi Sree Seana XAoztay =| “Oavao10p ‘NoOaYQ =| “VNVINOW | “COIMAd $$$ _80-6F9 ‘eg 86-0SF‘818‘0E$ | $8¢.1FE ‘seg 91.980°G6$ | S8.E0F‘9ES 19-690°FSF'SS | F9-T9L‘TESS | 29.c18°C19FS | Z8.69L‘SFS'TS | 8.999‘c6eg | TeIOT, 80.CF9'ES =| OF. 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LOL TESS “VNITOUVD ‘VIDUOUD HLAOY B9-G18°C1G FY “VNITOUVO HLYUON 68-69L'ShS'TS | 88.999'6S | © PINdTopelud ‘ATATIC ‘VINIDUIA woud “LNIW daLuvg ‘9981 “HLOG ANAL OL ‘SAHONVUT ANY SALVIS GALINA AHL JO LNIW AHL LY G109 OLLSAWOM JO SLISOMAA ANILNGA AHL JO LIGIHXD AUVWWOAS—'s ‘panwywg—NOTLOAGOYd OILSANOG AO GION AO LNAWALVLS CHAPTER V. MEXICO, CENTRAL AMERICA, AND SOUTH AMERICA. MEXICO PRE-EMINENTLY A SILVER-PRODUCING COUNTRY—NICARAGUA—CHONTALES MINING COMPANY—BRAZIL—ST. JOHN D’EL REY COMPANY—IMPERIAL BRAZILIAN ~ —DON PEBRO NORTH D’EL REY—ROSSA GRANDE GOLD MINING COMPANY—EAST D’EL REY—NEW GRANADA—MARIQUITA AND NEW GRANADA MINING COMPANY— PERU AND BOLIVIA. MEXIco is pre-eminently a silver-producing country, and almost the whole of the gold which it affords is found in combination with that metal. The amount of silver produced is, however, so large, that the associated gold becomes a matter of considerable importance, and will be more particularly referred to when treating of the ores of silver. The silver of Guanaxuato and Guadalupe y Calvo is rich in gold, whilst that of Tasco, Catorce, and Zacatecas is poor. In 1840 Duport estimated all the gold produced in Mexico, including that separated from silver, at 74;th of the production, by weight, of the latter metal and its value at 4th of that of the silver. There are some gold veins in Oaxaca, which have been worked for many years, and which Chevalier was of opinion would at some day become of importance. ’ CENTRAL AMERICA. But little is definitely known with regard to the auriferous districts of Central America, except that the gold washings of Costa Rica produce a certain amount of the precious metal, which is mostly smuggled out of the country, and consequently no estimate can be made of its amount. The only European Association professing to carry on gold-mining operations in Central America is, we believe, the following :— Nicaracusa.—The Chontales Gold and Silver Mining Company.—This Company was formed in 1865 to purchase and work gold and silver mines in the Chon- tales district of Nicaragua, a gold field hitherto unexplored by Europeans, although worked for several years by the inhabitants. The following description of the 78 GOLD. properties is condensed from the reports of Captain Paul, the mining agent who was sent out for the purpose of inspecting them, and who has since become the local manager. The San Domingo Mine comprises an extent of 1,000 varas on the course of the lodes, by 2,000 varas wide. There are two large well-defined auriferous and argenti- ferous veins running parallel with each other through this sett, about 50 varas apart. One lode has been worked, for about 100 yards in length, to the depth of 20 feet, on its entire width, and is said to have yielded from 1 to 10, and as high as even 100 oz. of gold per ton, while the general average is reported to be about 3 oz. per ton. The hard quartz, yielding nearly 2 oz. per ton, is stated to have been thrown aside, owing to inadequate means for grinding. The mine has, hitherto, been badly worked, and on a small scale, yet 230 oz. of gold were raised in the month of January, 1865. La Trinidad adjoins San Domingo on a parallel lode. It is 800 varas in length, by 100 in width. The workings are in a deep valley, so that a level can be driven, and 30 to 40 fathoms of backs obtained. This mine has hitherto been owned and worked by natives, who have not had the means of erecting proper machinery, and, in consequence, have been obliged to carry the ore to the mill on men’s backs. From 60 tons of ore they obtained 112 oz. of gold. A shaft has been sunk 27 varas, and levels have been driven at 9, 18, and 27 varas, and in each of them the lode is said to yield an average of 2 oz. per ton. The Cabezales sett, on a continuation of the Javali lode, is 1,200 yards in length, by 200 in width. In one place a shaft is sunk 21 feet een ae 8 feet square, on this lode, and has yielded 30 to 40 oz. of gold, extracted by the most primitive processes. Samples taken from the shaft are stated to average about one ounce per ton, and it is said:'an abundance of quartz can be obtained when the mine has been properly opened. Javali is situated about one and a half miles from San Domingo. An open cutting has been made in the lode, 60 or 70 yards in length, to the depth of from 5 to 20 feet, and 21 feet wide, still leaving a portion standing. The hard quartz, all of which contains sulphide of silver, and from half to three quarters of an ounce of gold per ton, has hitherto been thrown away, unless it contained visible gold, and there are from 1,500 to 2,000 tons of rock now at surface, which, with proper machinery, would yield a good profit. A new shaft is being sunk in the whole ground to get under the old workings, where the lode yields from 3 to 4, and even up to 40 ounces, per ton. At present only four mills are at work, with which they grind about 160 tons per month, and extract from 200 to 300 oz. of gold ; employing 40 to 50 men, most of whom are occupied in carrying the ore to the mill on their backs. Consuelo is about a mile from the San Domingo, and is 800 yards in length on the course of the lode, by 200 yards wide. A shaft has been sunk about 60 yards deep, and levels driven on the lode, at each eight yards in depth. The lode is not uniformly rich throughout its whole width, but the poorest parts will give at least half an ounce of gold per ton, while the richest, for three feet in width, will average 4 oz. per ton’; and taking the rich thread by itself, which is from three to six inches wide, it will Ted from 10 to 300 ounces per ton. San Antonio is on a parallel lode immediately to the north of the San Domingo, and adjoins La Trinidad to the west, being a continuation of the same lode. It is 800 yards in length on the course of the vein, by 200 yards wide. In January, 1865, 50 tons of ore yielded 123 oz. of gold ; and from the manner in which the ore was ground and amalgamated, it is believed a large quantity was lost. There are SOUTH AMERICA. 79 about 500 tons of ore on the surface, which will yield about 1 oz. per ton ; but, owing to the distance the present. workers have to carry it to the mill, it does not remunerate them. These mines have not, as yet, made either large or regular returns ; but, if the foregoing description of the property be correct, it should, with good management, afford large quantities of bullion at a very early date. SoutH AMERICA. The quantities of gold produced by the mines of South America have never been very large, although they at one time poured forth a stream of wealth, in the form of silver bullion, almost unparalleled in the history of the world. Humboldt estimated, in 1800, the whole produce of gold of the South American Continent at 33,524 Ibs., of which 9,900 ]bs. were furnished by Brazil; whilst, according to the same authority, the yield of silver during the same period amounted to 691,625 lbs.; the respective weights of the two metals being thus nearly in the ratio of 1: 29. In the year 1850, the yield of gold had further diminished to about three-fourths of what it was at the begin- ning of the century, and, according to Chevalier, the total yield of gold from Peru and Bolivia was, in weight, up to 1846, as compared with silver, in the ratio of 1 : 170. Brazit.—This country has long been famous for its gold mines, which have been worked from the beginning of the last century, and have, in the aggregate, produced very considerable amounts of the precious metal, ‘The large quantities of gold produced during the eighteenth century were almost exclusively the produce of the alluvial washings of Minas Geraes, but these have, to a great extent, become exhausted, and the gold now yielded by Brazil is almost entirely the result of deep mining in the solid rock, which is, for the most part, carried on by English capitalists. The auriferous deposits of Brazil differ considerably in their character from those of other parts of the world, since the gold is often rather disseminated in metalliferous beds, than enclosed in regular veins. The enclosing rocks are supposed to be of palzeozoic age, but they have been so changed by metamorphic action, as to render it impossible to assign them to any precise epoch. The gold-bearing district consists of a series of disconnected eleva- tions, which do not assume the appearance of a regular mountain- chain, and in which the eruptive rocks come to the surface in dome- 80 GOLD. like masses. The most generally prevailing formations are gneiss, and those varieties of rock, known in the country as ctacolwmite, jacotinga, and ztabirite. These are characteristic of the gold-bearing rocks of Brazil, and are not generally met with in the mines of either Cali- fornia or Australia, although some of the rocks of the Appalachian gold mines very closely resemble them. Itacolumite is a quartzose rock, intimately incorporated with particles of chlorite, and frequently occurring in bands of enormous thickness. When this rock includes specular iron in its composition, it becomes either itabirite or jacotinga, according as it is crystallised or compact in its structure. Throughout these metalliferous beds gold is disseminated, and those veins are generally most productive which contain deposits of quartz and specular iron. The most important of the Brazilian gold mines is the Morro Velho Mine, belonging to the St. John d’El Rey Company, where the various operations of mining and reduction are conducted on a very extensive scale. Through the kindness of Mr. Hockin, the Managing Director of this Company, we are enabled to. give the following particulars relative to the St. John d’El Rey Company’s Mines :— The St. John d’ El Rey Mining Company was first formed in 1830, for working, on lease, the mines of St. Joao d’El Rey and St. José near the town of the former name, in the southern part of the province of Minas Geraes, in the Empire of Brazil. These mines, having been found wholly unproductive, were abandoned in 1834, and the Company then purchased the Morro Velho mine and estate, situate at Congonhas, near Sabara, a considerable distance (a degree and a half of latitude) north of the locality of their first operations. The Morro Velho Mine had been previously worked by native proprietors for more than a century, chiefly by open cuttings, and with varied results. At the time of the purchase of the property by the St. John d’El Rey Company, the Morro Velho Mine was stated to be yielding a profit ; but a considerable outlay having been found necessary, in order to extend the operations and increase the resources of the mine, the Company, having had to expend large sums in the purchase of stock and erection of buildings, &c., worked at a loss during the first four years of its possession of the estate. In 1839, the returns, under the management of the late Mr. C. Herring, to whose judgment the Company is indebted for the selection of the property, again exceeded the outlay ; but the original capital having been exhausted by the losses incurred at the St. John d’El Rey mines, and the purchase of the Morro Velho property, it was found necessary to apply the greater portion of the proceeds of the gold extracted, to the extension of plant, and it was not until 1842 that the first dividend was declared. From that date, with the exception of an interval of eighteen months on one occa- sion (1857-8), and twelve months on another (1864-5), during which the working of the most productive portion of the lode was interrupted by a breakage of the pumping and other machinery, the Company has regularly paid dividends every six months. SOUTH AMERICA. 81 The original subscribed capital of the Company was. . . . £135,000 Out of which there was returned to the proprietors . . . . 6,600 Prema UP CAMA oe ge ee Fees ey») 128,400 There has been paid in dividends . . . . £756,245 Laid out in machinery and buildings on the propery it of protix 140,000 Stores existing on the property of the value of. . . .. . 39,000 A reserve fund and working capital has been provided, out eeeetimO PNGOXLEND Of) sce ds e- ‘ns pee ote 7) ye 72,249 Meakine.total profit. . 5 ee ew? a, l,007;494 The total value of the precious metals extracted from the mine hasbeen ... . em tall dt eee) ee Ue ed The total amount of mineral nied Soh. ae sees. - 1,769,050 tons The average yield of the ore . . . . . . 4'333 oitavas per ton. Or as nearly as possible half an oz. fies en sin 32s. 6d.* The ores from which these results have been obtained, as will be seen by the following figures, have been, on the whole, poor; the yield has been tolerably uniform, the variations that have occurred being attributable rather to the propor- tion of slate ground with the ore, than to any fluctuation in the quality of the lode itself. Improvements have, from time to time, been made in the mode of treatment, and the loss sustained has been, year by year, steadily reduced. The average yield of gold per ton, in oitavas, on the whole quantity of stone annually brought to the surface since the year 1847, has been as follows :— Years. Oitavas.t | Years. Oitavas. Oy 9 Se ee eae 1a Of ES ie Mi er eater meee Py Mirpars f O, 65 eee ote kk) My pind woo’ OD Dee ei, tg OPO dy aa cao Beer et haw ds ot . (4°07 REGO ay AveOint ce be btae eek) Seao Pees! ge qu fl hs OOo LEGS sed Mee cr teem” chavs ae eet eo Ss is oe ay ABS LAG Trcic aber eee eh eet eee Fat eel eles a ye 44 LOG Cea re Aut fa we ee Pe soe sk, TZ LNs 51 ae ee or Ge a A Se: See ete eee re i 1 corOS Be oo) An ie. te es ene rs 58 Pete’. Prahlss ia. sys oe h2 LeU itor ttnn bor pie ko). tl It should be stated, with reference to these figures, that they do not furnish reliable data whereon to form a judgment as to the increasing or diminishing produce of the auriferous formation in depth, inasmuch as, until recently, no account has’ been kept of the quantity of clay slate or other unproductive stone raised from the mines. During the last six years, excluding 1864, during which a large portion of the killas or clay slate was stamped with the ore, this unproductive stone * The gold obtained at Morro Velho is usually alloyed with about 20 per cent. of silver. + An oitava is 2 dwt. 7°343 er. Troy, or 8°67425 oitavas = 1 oz. Troy. G 82 GOLD. has been treated separately, and the proportion it bore to the whole quantity of stuff raised has been as follows, viz. :— Years. Per Cent. Years. - Per Cent. RO rs eae eh ee oP en 1863.0... 2. 2 Se Mee es cel, CER ae iy fe See Meee 1864 '00 4 6 eo MN Oc oR. go hak ol Satan) eepeteane 1865. 2. . .9, 4) SS Whether during previous years, the quantity of this comparatively unpro- ductive stone was in excess, or otherwise, of the foregoing, there is no means of ascertaining. The formation affording the gold is a strong, well-detined lode, though irregular in direction, dip, and dimensions ; its inclination or underlie has also been found to vary at different depths, and in different parts of its extent. The vein- stone is mostly composed of quartz with iron pyrites, disseminated, more or less regularly, throughout its mass, and the lode is not unfrequently traversed by clay slate and barren white quartz. When pyrites is absent in these rocks, gold is seldom present.* In some places the vein is cavernous, and legs close in its texture than in others ; but where drusy cavities are frequent, the yield of gold diminishes : the most pro- ductive matrix for gold is a compact mixture of quartz and pyrites, with varying quantities. of slate. The great metalliferous deposit called the Cachoeira, Bahu, and Quebra Panella, is one continuous, very irregular vein, varying in width from seven to seventy feet, and at one point reaching 100 feet. The average thickness at the present depth, 176 fathoms perpendicular on the Cachoeira, and 165 fathoms on the Bahu, is 19 feet : the stoping space extends over 807 square fathoms. There is a north branch, separated from the main deposit by the enclosing rock called the Gamba, but its working, having been found unprofitable, has been discontinued. The enclosing rock is a clay slate of tolerably uniform texture. The shafts, so-called, for the whole of the lode has been excavated from the surface, are carried down at an inclination of about 45°, and the mineral is brought to the surface by tram carriages of a peculiar construction, carrying large kibbes, containing a ton each. The mineral brought to the surface is first freed from slate and other unproductive stone on the spalling floors, and the ore, after being broken to a uniform size, is. stamped fine. The rejected slate and quartz is removed by tramways to another establishment, half a mile distant, and there employed to assist in the further pulverisation of the refuse sand from the first stamping, which is re-stamped. The stamping mills, as is also the pumping and other machinery, are moved by water-power. The pulverised ore, issuing from the stamp coffers, through finely perforated copper grates, passes over bullock skins, in the first instance, and lower down the inclined tables, over woollen cloths. The bullock skins are taken up and washed in vats every hour, and the woollen cloths at longer intervals. The concen- trated sand resulting from washing the bullock skins, is subsequently amalgamated in barrels. The subjoined table shows the quantities of rock raised and stamped, the amounts of gold produced, and annual net profits made since 1848. * Arsenical, magnetic, and ordinary iron pyrites predominate at different points, and in varying quantities ; carbonate of lime, dolomite brown spar, and, very rarely, copper pyrites, are also present in the vein. SOUTH AMERICA. 83 ‘ capa aoe oti 2 oe See a ea leh 1849, | 1850. | 1851. | 1852. | 1853. | 1854. /asss, 1856. | 1857. Stone raised, tons . . . . . . . . |67,336/67,106 79,810|82,642)85, 698] 86,048|87,297|89,877 86,407 Stone and Ore stamped, tons . . - . (69,004 64,313)81,629|81, 236]/86,866|86,433/86,848/87,424 86,335 Gold produced, lbs. Troy . . .. . 2,583) 2,517| 3,057) 3,323] 3,623] 8,464) 3,325) 2,999 2,539 ) bald Le piel eee esas £ £ £ £ £& £ £ PO ETORG es sk hak kk ke 38,136/35,880/51,586|55,391/49,273/44,740 34,466/23,233| 787 — = — SSS SEES = ——————_—— 1858. | 1859. | 1860. | 1861. | 1862. | 1863. | 1864. | 1865. | A a Aue | Stone raised, tons. . . . . . . . |88,901/88,968/91,361/96,612 90,896|84,758|65,435/78,883 Stone and Ore stamped, tons . . . . |87,270|82,880)74,528/71,902 67,508 65,697|62,147|59,607 Gold produced, lbs. Troy . . . . . | 2,733! 3,294/°3,974! 5,051| 5,189 4,713] 2,852) 4,153 £ £ £ £ £ £ £ £ Net Profit. . . . . . . . . . « | 8,545/38,058|60,460|96,769)87,531/63,285| ... |go,438 DRC S S ie SE i 4 ne ose ge saa oo 114,629 Since 1860 the slate and other unproductive stone has been rejected, and the ore only stamped. The clay slate thus separated is crushed in another department of the works. In the above table the profit for that year has been calculated on accounts made up to the end of February, whilst the other figures given are the result of operations up to the end of December in each year. This company employs upwards of 2,400 hands, from 120 to 130 of whom are Europeans. The number of stamp heads at work is 135, for reducing the ore in the first instance, and 56 for re-stamping the residual sand, with slate and quartz : arrastres are also used for re-pulverising the residual sand, and are found very efficient for that purpose. The work performed by the stamps is given in the following table ;— 1865. TABLE OF STAMPS DUTY. | | | | | | Sat z Tons | Pounds | STAMPS. | Heads. Oh He wend’ | of Ore |Tons per Day. |per Head] | | B- stamped. per cae f lyow . 30 | 56 | 357-46 | 12,1006 33°85 2,527 | Cotesworth . 12 59 | 356-00 | 4,939-1 13°85 2,585 | Susanna } 9 60 | 36112 | 2,897-2 802 | 1,996 | | Herring | 4 77 =| 357-29 i 31°89 | 2,976 | Powles . . 36 64 | 351-24 | 17,5626 50-00 3,111 Addison . . 24 67 | 353°52 | 10,619°8 30°04 2,803 Totals. 5 }~196 | ee | — |59,607°3! 167-65 | _ | 8 4 GOLD. Imperial Brazilian Mining Association.—This Company was formed in 1825, for the purpose of working the Gongo Soco and other mines in the province of Minas Geraes, and in the course of fifteen years produced nearly a million sterling. The following is a statement of the financial operations of the Imperial Brazilian Mines ‘Association at Gongo Soco, from Ist J eran 1826, to 3lst December, 1856 : *— RECEIPTS. Proceeds of gold dust... 06-64 ss 5 wigs se rr PAYMENTS. Salaries and wages. . . . . £482,942 Materials: 0 eo! yee Cage he ees ee Se eae Provincial duties paid Brazilian Goverament-<. {+ 420 9 2 = B80 a7 Export duties, ditto .°. . . 22,4038 Hes BONGO | Actual profits ee Gold was discovered at the surface 122 fathoms above the bottom of the mines, but, owing to the slope of the ground, the deepest shaft was only 56 fathoms in depth ; and for the last eight or ten fathoms, the vein, which had entirely changed its character, afforded only a few particles of ane ‘i Don Pedro North @El Rey.—This Gotnnany was, on the recommendation of Captain Treloar, formed in 1863, for the purpose of purchasing and working the mine of Morro de Santa Anna. This gold mine forms a portion of the celebrated range of mountains called the Sierra de Itacolumi. The mine is about six miles north from Ouro Preto, the capital of the province of Minas Geraes, and two miles, west, from the cathedral city of Marianna. It is distant from the St. John @El Rey Company’s mine, Morro Velho, about forty miles in a southerly and easterly direction. The holding, or partition of the mining concession in this locality, differs from that of similar property generally in Minas Geraes. In 1762, permission was given by the Government to open mines in this mountain, wherever the miners might feel inclined, and on doing so they became the lawful possessors of fifty palmos of ground on each side of tet: levels and shafts. Owing to this, the mountain is studded with mines, which the owners from time to time went on selling, until, with a few unimportant exceptions, the whole became the property of the present Company. At one period, upwards of 5,000 miners were working on this mountain, and, in order to extract the precious metal, most of them crushed the mineral obtained by hand, and it must therefore have been rich to have repaid them for their trouble. The mountain of Morro de Santa Anna rises some 2,000 feet above the valley, but behind it there are still higher mountains, and the mine is consequently well pro- vided with water; water is brought in at different levels, and more could be obtained if required. Near the summit the mountain has been, in most places, * Communicated by W. J. Henwood, F.R.S. + This mine was ultimately abandoned, about the year 1858, on account of its poverty. oa ae SOUTH AMERICA, 85 completely honeycombed ; but downwards, the auriferous formations are entire for a considerable elevation above the valley. The Morro de Santa Anna contains three auriferous formations ; two of them are of jacotinga, and the third is a rock formation. All three have yielded large quantities of gold, but the rock, with the jacotinga next it, have been most productive. The face of the mountain is covered with canga, an iron conglomerate, about four feet thick ; this is auriferous, and will probably pay for stamping. Beneath the canga is the first jacotinga formation, about 60 feet in thickness, containing veins rich in the precious metal; the jacotinga partakes more of the character of mica slate, than of iron sand, and the auriferous veins in it are more like quartz than ironstone. This rests on a stratum of hard ironstone about three feet in thickness, which is the second jacotinga formation, but quartz is the pre- dominating constituent, and rock is, according to Captain Treloar, a more correct name for it than jacotinga. This lode averages about four feet wide ; it opens and contracts, and where it expands it is generally found most productive. Subjacent to the latter, is a layer of hard clay and mica slate, of about five feet in thickness, and then comes the rock formation, which has yielded the chief returns of gold. In the present workings, it is about ten feet wide ; but in its longitudinal, course, it so expands and contracts as to become in some places extinct. Where it expands, the dip is northerly. Besides these, there is another lode in the hill on the opposite side of the valley, at a place called Maquine. Of this lode but little is known ; a very large stream of water is issuing from it, and reports say that large quantities of gold, and some nuggets, have been found at the foot of the hill. The general direction of the lodes at Morro de Santa Anna may be said to be easterly and westerly, and their underlie northerly, but both vary, owing to the lodes hugging the contour of the mountain. The late proprietors worked only on a small scale, and on account of their want of knowledge of mining, chiefly confined their operations, during the last three years, to one canudo. The first of these three years was mainly devoted to clearing the workings, shifting stamping mill, and other preliminary operations, but even during this ate the chief proprietor is said to have made a profit of £7,600. The fossa Grande Gold Mining Company.—This Company was formed in 1864, to work an extensive mineral property, called Rossa Grande, in which are said to be several gold mines, The estate is situated in the province of Minas Geraes, in the vicinity of the mine of Morro Velho. The city of Sabara and several Pillaves are within easy walking distances of the property, and the road from Gongo Soco to Sabara and the St. John d’El Rey Company’s mines passes through it. It is of great extent, and is estimated to comprise an area exceeding twenty-one square miles, or aver 13,000 acres. The climate is said to be salubriane and the character- istics of the ae similar to those of the Morro Velho Mine. The estate contains three distinct auriferous rock formations, which can be traced for miles, besides a jacotinga formation in the direction of Gongo Soco. Diamonds are said to have been found, and the alluvial deposit in the valley is believed to contain sufficient gold to rink it remunerative for working. The first rock forma- tion, or upper ine, is about six feet wide. It consists ahiel of white quartz and iron, and has yielded from four to forty oitavas, or from half an ounce to five ounces of sold per ton. The second rock formation, or middle lode, varies in size from six to twelve feet. It is composed chiefly of quartz and aierdes arsenical pyrites. Lumps of gold have been found in it, and the ore in the swells has sometimes afforded fifty oitavas 86 GOLD. or upwards of six ounces of gold per ton. The third, or lower rock formation, is of greater magnitude than the other two, being about thirty-six feet wide. Its compo- sition is mainly quartz and brown oxide of iron. The whole mass of this lode is said to be auriferous, and portions of it have yielded fifty oitavas of gold per ton. This mine has not yet produced any considerable amount of gold : the greater portion of the time which has elapsed since the formation of the Company, has been occupied in clearing out the old workings, and the erection of machinery. East @ El Rey Company.—The Morro Sad Vicente Mine, worked by this Company since 1863, is situated about twenty-four miles eastward of the Morro Velho Mine, and about twenty-two miles from Ouro Preto, the capital of the province of Minas. The highway to the latter from the interior passes through the estate, and the distance from the Emily Mines, formerly worked by this Company, is about seven- teen miles. The estate contains several lodes, but the Champion Lode is considered to be more important than the others. The mine is on this lode, which runs obliquely to the cleavage planes of the containing rock ; its course being 8. 50° E., and underlie north, at an angle of 45°. This vein belongs to the class of auriferous rock formations. It chiefly consists of quartz, pyrites, galena, tellurium, and gold ; it can be traced for some miles, and its width varies from twelve to thirty feet. The rich shoots dip eastward, at an angle of 40°; the containing rock is clay slate. The mine is situated in a deep hollow, near the western boundary of the property, and, consequently, does not admit of drainage by an adit; pumping machinery, therefore, is used for this purpose. The excavation has gone down at a less slope than the dip of the lode, and, consequently, it has passed from one layer of the vein into another above it, and, since the returns of gold have been much higher in some months than during others, it follows that they vary in richness ; yet, on the whole, the mine has been generally found to improve in descending. Its present depth is about 100 fathoms. This pro- perty has, until very recently, made regular returns of gold ; but having, in common with other mines in the district, suffered much from want of workmen, who, in consequence of the war in which Brazil is now engaged, have been draughted for military service, it has been obliged temporarily to suspend operations. The value of the gold remitted to England during the time the Emily Mine was being worked by this Company, amounted to 5,306/. 15s. 5d. From the Morro Sa6 Vicente : Eat: ee Tn 1864.54 2 22).4> 98597 1865, to May 1866 8,588 17 6 Total £11,441 4 10 —— Brazil afforded its largest yield of gold about the middle of the eighteenth century, and from 1752 to 1761 the amount on which the royal fifth was paid, varied from 17,000 to 21,500 lbs, yearly. The production from that time fell gradually off, until in 1822 it was less than 1,000 lbs. From 1810 to 1817, the mean- annual production of Minas Geraes, by far the most productive mining district of the country, 1s given by Humboldt as having been 4,288 lbs. SOUTH AMERICA. Si The gold at present produced in Brazil is almost exclusively obtained by the various large English companies, and particularly that of the St. John @’El Rey, from deep mining. NEw GRANADA—From the year 1819 to 1831, the ancient vice- royalty of New Granada was united with Venezuela, and during a portion of the time with Equador, forming the republic of Columbia, but is now, in common with each of the other States, nominally an independent republic. The mines of New Granada have been well déscribed by Boussingault, Chevalier, and others, but we are without much recent information on this subject. The principal washings are situated in the provinces of Antioquia and Veraguas, in the former of which the detritus of all the rivers is said to be auriferous; and some quartz veins occurring in granite, and containing iron pyrites, are worked on a limited scale. The principal mines of gold quartz worked in 1850 were on the river Porce, the veins resembling in every respect the quartz lodes of other auriferous regions, and containing a con- siderable amount of iron pyrites, and other sulphides. Quartz veins are also numerous in the provinces of Panama and Veraguas, but the amount of gold contained in them is usually small. Chevalier esti- mated the yield of the Province of .Antioquia for the year 1847-8 at 12,500 Ibs. Mr. Danson,* from information based on the returns of the British Consuls, estimates the total amount produced from 1804 to 1848 at 40,817,066/. There is abundant evidence, however, that New Granada is rich in gold ; and with a healthy climate, more energetic inhabitants, and a better government, there is no doubt that it would have annually produced large quantities of the precious metal. Various English Companies have at different times worked mines in New Granada, and even within the last twelve months discoveries were made of placer diggings, which attracted the general attention of Californian miners, and caused them to immigrate to the country in considerable numbers. We believe, however, that the results obtained were not generally satisfactory, and that the diggings were very unhealthy. Mariquita and New Granada Mining Company.—The most important gold mines belonging to British capitalists now worked in New Granada are those of Marmato, which are situated in the province of Antioquia. Previous to 1852, these mines were worked by an independent company, but in that year the above association was * Journal Stat. Society of London, xiv. 40, quoted by Whitney. 88 . GOLD. formed, for the double purpose of working the Marmato gold mine and the Santa Ana silver mine, both in New Granada. . Atthe time of their purchase by the present proprietors, the mines of Marmato were provided with twelve stamping mills, representing, in the aggregate, 110 heads ; which, during the year 1851, had crushed 12,488 tons of stuff, yielding on an average lldwt. llgr. of fine gold per ton, and resulting in a net profit of 8,3431. 6s. 8d. The Marmato mines are worked on deposits of auriferous pyrites, usually yielding a little more than half an ounce of gold per ton. The quantity of ore raised during the year ending March 1853, was 15,056 tons, and the quantity stamped 19,089 * tons, the total produce being, gold, 10,711 oz. ; silver, 5,988 oz., leaving a profit of 11,4492. 10s. 2d. During the financial year ending March 1854, the ores raised amounted to 17,372 tons, and the quantity stamped to 18,225 tons, yielding gold, 10,170 02. 5 silver, 5,895 oz., and resulting in a net profit of 9,7671. 13s. 9d. From March 1854 to 1855, the ores raised amounted to 14,154 tons, and the ores stamped to 18,288 tons, which produced 6,608 oz. of fine gold, and 4,193 oz. of silver ; the profit for the year being 3,932/. 5s.7d. In the following year, the ores raised amounted to 15,966 tons, and the quantity stamped to 17,668 tons, yielding 6,408 oz. fine gold, and 4,193 oz. of silver, and leaving a profit of 5551. 14s. 2d. on the operations of the twelve months. During the year ending March 1857, the ore stamped amounted to 19,370 tons, yielding 5,635 oz. of gold and 3,353 oz. of silver, leaving a profit of 2,184/. 19s. From this period to March 1858, 14,820 tons of ore were crushed, and 4,743 oz. of gold and 2,852 oz. of silver obtained ; but resulting in a profit of only 5411. Os. 8d., as a large amount of machinery was erected in the course of this year. In 1859 the profits were 1,918/. 12s. 5d., the stuff crushed, 19,598 tons, the gold obtained, 6,476 oz., and the silver, 3,874 oz. The profits im 1860 amounted to 2.7781. 8s. 4d., but we have no data relative to the amount of ore treated, &c. For the year ending March 1861, the profit was 1,083/. 18s. 5d.; the number of tons crushed, 19,431 the yield of gold, 5,059 oz., and of silver, 3,150 oz. From the 28th February, 1861, to 24th of January, 1862, the operations of the mines were much interfered with by the Revolutionary War: only 16,859 tons of rock were crushed, and 2,592 oz. of gold, and 1,663 oz. of silver obtained. The loss on the operations of this year amounted to 2,745/. 15s. 9d., and they were afterwards for some time almost suspended. After the termination of the revolutionary movement, the works were again resumed, and between 31st March, 1864, and 31st March, 1865, 10,283 tons of stuff were crushed, and about 3,000 oz. of gold and 1,800 oz. of silver obtained, but the returns were not sufficient to meet the outlay. The Marmato property is at the present time being worked at a profit, and the Company has recently acquired the Aguacatal mines, in the immediate neighbourhood, from which satisfactory results are anticipated. ~ Preru.—Gold is found in many of the mountain passes, and nearly all its rivers wash down auriferous sands. Some of the richest gold diggings of the country are about Huaylas and Tarma. It is difficult to estimate with any degree of exactitude the amount of gold annually * The number of tons crushed is always in excess of the weight of ore raised, as some of it is stamped more than once. SOUTH AMERICA. 89 obtained in this country, the business of gold washing being carried on almost wholly by the Indians ; but it is believed that the yearly production is somewhere about 2,400 lbs. Troy. In the valley of the river Chuquiaguillo the alluviums appear to be due to the abrasion of Silurian rocks, and are stated by Forbes to be eminently auriferous.* These have been worked from a very remote period, and the great quantities of gold found in Peru at the time of the Spanish con- quest, had been, in great part, if not entirely, derived from detrital accumulations. | The rabbit-like burrows made by the Indian gold miners into the more auriferous beds, are still everywhere visible along the sides of valleys, where a supply of water was not too distant to admit of their transporting the pay dirt for the purpose of being washed; and later explorations have not unfrequently disclosed the mummies or skeletons of Indians who have, in these narrow and tortuous holes, perished from the falling in of the superincumbent earth, and have been buried along with their tools and mining implements. The gold washings in the valley of the Chuquiaguillo are at present conducted in the fol- lowing way. The valley is, in the first instance, completely closed up, _ and the course of the river stopped by a rude wall or dam of stones and earth, provided with sluices, and having a portion of the wall somewhat lower, in order to serve as an overflow for any excess of water which may be collected. A longitudinal excavation is then made, close up to one side of the valley, of such a breadth as can be conveniently carried on by the number of hands employed on the works, and any stones or boulders that may be met with, too heavy to be carried off by the rush of water, are piled on one side, whilst the earth, sand clay, and gravel are removed by the force of the stream. On arriving at the several successive auriferous beds, the positions of which are known beforehand, from the results of previous trials, more care is taken in washing; but the whole of the pay dirt is flushed off, and, being heavier than the other constituents of the bank, deposits itself at a short distance from the workings. Here it is collected, and sub- jected to repeated washings in wooden troughs, until nothing but the grains of metallic gold remain behind. The excavation is in this way gradually deepened, until the lowest available auriferous stratum has been reached, when the operations are abandoned, in order to commence similar washings on a line parallel “ Report on the Geology of South America, by David Forbes, F.R.S., com- municated to the Geological Society, November 21st, 1860. 90 GOLD. with the first opening. Any stones or boulders met with in the new workings are thrown into the old one, and the excavation is thus carried directly across the valley. Botivia.—Gold is found in many of the streams that flow down the eastern side of the cordillera, and at Choquecameta, near Cocha- bamba, at the sources of the Rio Grande, as well as at Tipoani, near Sorata; and in some other localities, the washing of auriferous sands is still carried on with profit. The gold-bearing strata occurring in the detrital accumulations of Bolivia, are generally known by the name of veneros, being, as it were, floors, or clay bottoms, on which gold had become deposited previous to its being covered by alternat- ing beds of sand, gravel, and boulders. Above the first of these there are sometimes one or more similar deposits, again covered by layers of sand and gravel. The diggings are entirely confined to the sides of valleys and the beds of rivers, which afford the necessary supply of water for washing. The celebrated washings of Tipoani and those of Yungas appear to belong to diluvial accumulations of the same geological age. There “are no means of ascertaining the amount of gold annually obtained from the various mining districts of Bolivia, but the total produce is probably about 1,600 lbs. Troy. Chili annually affords a considerable amount of gold, but we are without any reliable information of a recent date relative to the gold mines of that country. Humboldt estimated its yearly produce, in’ 1800, at 7,500 lbs. Troy. CHAPTER VI. BRITISH POSSESSIONS.—NORTH AMERICAN COLONIES. DISCOVERY OF GOLD IN NOVA SCOTIA—GEOLOGY OF GOLD REGION— CORRUGATED QUARTZ AT WAVERLY—IMPRACTICABLE MINING LAWS—STATISTICS OF GOLD OBTAINED—CANADIAN GOLD FIELDS—PRINCIPAL GOLD WASHINGS IN CANADA —REPORT OF PARLIAMENTARY COMMITTEE—DISCOVERY OF GOLD 1N BRITISH COLUMBIA—EXTENT OF THE GOLD FIELDS—GOLD CHIEFLY OBTAINED FROM ALLUVIAL DIGGINGS, Nova Scotta.—The whole of the Atlantic shore of this Province is bordered in an unbroken line by strata of a metamorphic character and probably of considerable geological antiquity, frequently broken through by eruptive rocks. These form a coast, in some places low and rugged, and in others boldly undulating; the goil is generally - rocky and sterile, although there are large tracts well covered with timber, and affording prosperous agricultural settlements, Along the Atlantic shore, this district is generally low, gradually rising to a height of some three hundred feet, as it advances northward. Its coast line has, according to Dr. Dawson, a general direction of south 68° west, whilst its inland boundary, although presenting some consider- able undulations, has a direction of south 80° west. The extreme breadth of this band, at Cape Canso, its northern extremity, is about eight miles ; whilst, in its extension westward, it gradually increases, until at the west branch of St. Mary’s River, eighty miles west of Cape Canso, it is known to be thirty miles wide. In the western counties its width has not yet been accurately ascertained, but here its entire _ breadth cannot be far short of fifty miles. Its total length corre- sponds with that of the peninsula of Nova Scotia. This band, in which almost the whole of the gold discovered has been found, chiefly consists of thick bands of slate and quartzite, highly inclined, and having a general north-east and south-west. strike. In different localities these rocks, which probably belong to the Silurian epoch, have ‘been penetrated by masses of granite, and in their vicinity the quartzites and clay slates usually present a highly metamorphosed appearance, 92 GOLD. Since the gold discoveries in California and Australia have been generally known, and public attention has been directed to the con- ditions under which deposits of the precious metal usually occur, reports of similar discoveries have, from time to time, locally arisen in different parts of Nova Scotia. In every instance, however, either mica or iron pyrites would appear to have been mistaken for gold. Some years since, also, a considerable excitement was caused by an article in Blackwood’s Magazine, in which it was affirmed that gold would be found in the hills to the south of Annapolis, and com- parisons were instituted between that locality and the Valley of the Sacramento. Many persons were induced by this article to leave their ordinary occupations to seek for gold, but their researches having in all cases proved unsuccessful, the fever gradually subsided, and the subject was ultimately forgotten. It is also worthy of remark, that Dr. Dawson, so long ago as 1855, when describing the great metamorphic band, observes, “Quartz veins, however, occur abundantly in some parts of this district, and it would not be won- derful if some of them should be found to be auriferous.”* There is, nevertheless, no authentic evidence of the discovery of the precious metal in the province previous to 1860, when some hundreds of persons, tempted by rumours of gold having been found, com- menced exploring near the head waters of the Tangier river. The amount of gold obtained in this locality was, however, so small that the miners ultimately became discouraged, and the excitement gradually subsided. In the month of March, 1861, a man who was stooping to drink at a brook, observed a piece of gold among the pebbles at the bottom, and, having picked it up, searched and found more. This took place about a mile to the east of the Tangier river. From this date attention became directed to the locality, numerous claims were taken up, and considerable quantities of gold were obtained by breaking the quartz with hammers, and washing the resulting dust in tin pans. 3 I June, the discovery of gold was reported near Lunenburg, at a locality called the Ovens. The veins at this place, although generally - small, are frequently highly auriferous, and appear to cross each other in almost all directions in a metamorphic slate belonging to the great southern band. On these discoveries being made known, numerous claims were immediately taken up, and various small Companies * Acadian Geology, p. 362. BRITISH NORTH AMERICAN COLONIES. 93 formed for working the veins, presenting themselves numerously in the cliff. Shortly after the discovery of the auriferous nature of the quartz veins, it was found that the sands on the beach beneath the headland also contained large quantities of gold; here claims were likewise rapidly staked off, and worked by means of cradles, so that the agere- gate daily yield from the several shore operations soon reached one hundred ounces. Gold discoveries subsequently followed each other in rapid succession, at Lawrencetown, Dartmouth, Sheet Harbour, Tsaac’s Harbour, Sherbrooke, Waverly, and Oldham. | The most remarkable deposit of auriferous quartz hitherto found in Nova Scotia is undoubtedly that on Laidlaw’s Farm, at Waverly. Fig. 4. CORRUGATED Quartz, LAIDLAW’s Farm, WAVERLY. (From a Photograph.) The principal workings are here situated near the summit of a hill composed of hard metamorphic shales, where openings have been made to the depth of some ten or twelve feet upon a nearly hori- zontal bed of corrugated quartz, of from eight to ten inches in thickness. This auriferous deposit, which is represented Fig. 4, is Q4 GOLD. entirely different from anything we have seen elsewhere, and when laid open, presented the appearance of trees or logs of wood laid together, side by side, after the manner of an American corduroy road. From this circumstance, the miners have applied the name of “barrel quartz” to the formation, which in many cases presents an appearance not unlike a series of small casks laid together, side by side, and end to end. The rock covering this remarkable horizontal deposit is exceedingly hard, but beneath it, for some little distance, itis softer, and somewhat less fissile. The quartz is itself foliated parallel to the lines of curvature, and exhibits a tendency to break in accordance with these stria. The headings, and particularly the upper surfaces of the corrugations, are generally covered by a thin, bark-like coating of brown oxide of iron, which is frequently seen to enclose numerous particles of coarse gold, and the quartz in the vicinity of this oxide of iron is itself highly auriferous. The other gold veins ot the Province present, generally speaking, few distinctive peculiarities, and very closely resemble those found in California and Australia. Their general course is north 60° west, and their dip towards the south-west, but there are not unfrequent exceptions to this rule. In addition to gold, the most auriferous veins of Nova Scotia con- tain variable quantities of iron pyrites, mispickel, galena, blende, and, less frequently, a small proportion of argentiferous and auriferous sulphide of copper. Here, as elsewhere, the presence of the sulphides is regarded as a favourable indication of the richness of a gold vein; and a lead, containing much disseminated galena, almost invariably yields a certain quantity of gold. The productive veins hitherto discovered have, as before stated, been found in the older rocks on the Atlantic shore, and commonly occur in parallel groups, near the centre of which, and parallel to the productive veins, a large reef of crystallised and comparatively unpro- ductive quartz, is in many instances found to run. These large courses are locally called “bull veins,” and usually contain small quantities only of the precious metal. The attention of the Nova Scotia gold miner has, contrary to the usual practice, been almost entirely directed, to the exploration of veins of gold quartz, and allu- vial digging has consequently been almost entirely neglected. There is, however, reason to believe that a careful examination of the alluvial deposits might lead to the discovery of gold. The thickness of the BRITISH NORTH AMERICAN COLONIES. 95 auriferous veins of this colony is less than those of California and some other countries, but they often contain visible gold. In 1861, considerable excitement prevailed in the Colony with regard to the gold discoveries ; and portions of the country, particu- larly those in the vicinity of Lunenburg, Tangier, Waverly, Lawrence- town, Sherbrooke, Sheet Harbour, and Isaac’s Harbour, were staked off into claims, and more or less worked at a very shallow depth. Several Companies were also established with a view to quartz mining on a more extensive scale; but although many of the veins were found sufficiently auriferous to have warranted more extensive and systematic exploration, the larger Companies were not generally successful. This result appears to have been, in a great measure, the effect of the injudicious nature of the mining laws framed by the local Government, which limited the size of the claims to an exceed- ingly small area; and a somewhat heavy tax charged on each, ren- dered the prosecution of deep mining all but impossible. Nearly every man in the Colony thus became the possessor of one or more claims, which could only be taken up in accordance with certain maps prepared by the County Surveyor, by whom each district was laid out in parallelograms almost irrespective of the nature and position of the leads; and consequently, the larger Companies, if desirous to obtain a mining field of suitable extent, had to buy out, at a large price, numerous small claim-owners, who, although they could not work their several minute holdings, did not scruple to demand for them an exorbitant sum of money. It also not unfrequently happened that some claim-owner, whose fragmentary holding was so situated as to render it a necessity for the efficient working of a large location, took advantage of his position to refuse to sell except for an extortionate amount. It is evident that such a system was totally incompatible with the rapid development of the mineral resources of the Colony, which, as a natural consequence, were most unfavourably affected thereby ; but when these obstacles shall have been gradually removed, and reason- able laws lave been enacted, there appears to be no reason for beliey- ing that gold mining will not become one of the profitable and lasting industries of Nova Scotia. The beach diggings near Lunenburg, which were at one time the most productive, have long since been, to a great extent, exhausted ; but many of the associations organised for the purpose of mining and reducing auriferous quartz, still continue their operations,although, it is believed, with somewhat variable success. 96 GOLD. The following are the official returns of-gold obtained from Nova Scotia :— PaaS Sia ae a seer = i lip ss | | | ; | | ig ia ~~ Be | ks) | a pet estes oe 4 - | je i f aN ~ © vA 3 oO | Sy /PiEl hc EB = = sble cle ae ES Bee 3 | PERIOD. Teal io as 2 ge = o&' 6/8/38 Se ks} there he oD 3 D) es pana 7 ie Sl aiiee| oh . S | ms D oO 1M i | ES ea tes | ed & iS) ie) f 4 ls | eH y a ee ea fas ree i | Tons. ewt. lbs.'oz. dwt. gr.'oz. dwt. gr./oz. dwt. pr. Year ending Dec. 31, 1862 . . . |484/8018)12, 6,401 0 0/1 1 1 i311 .O- 01-7276 -OnG a * S 1868 . . .. | 877 185 25 10/17, 001 1415 | 0°16 12 | 28 0 ONNe OGiete a7 Nine Months ending Sept. 30, 1864 | 830 |35 23/1215,316 14 0/0 19 0/| 88 11 8 |14,565 9 8 Year x ¥; 1865 | 692 |33 23,10|23,835 11 Oj1 O 21 (141 0. 7 \24,867 «6 22 , CanapA.—The existence of gold in Canada first attracted public _ attention in 1847, although it is stated that M. de Léry, a French Canadian, had found specimens of this metal long previous to that date. In 1850, a considerable amount of local excitement was caused by the discovery of alluvial gold in the detritus of the Chaudiére and various neighbouring streams ; and an association, under the title of the “Chaudiere Gold Mining Company,” was formed for the purpose of washing gold in that district. In 1851, specimens of gold were shown in the Great Exhibition of that year, by Sir W. Logan, the Government Geologist, and the then recently formed Chaudiere Com- pany. In addition to the Chaudicre, other localities have afforded this metal; among these may be mentioned St. Francis Beauce, Aubert-Gallion, Sherbrooke, and Melbourne. ‘The auriferous region, according to Sir W. Logan, covers an area of from 3,000 to 4,000 square miles, and appears to occupy a great part of that portion of the province lying on the north-eastern side of the prolongation of the Green Mountains into Canada, extending up to the boundary line separating that colony from the United States. The greater portion of the gold hitherto obtained has been procured from superficial washings, none of the quartz veins which occur in the district having been extensively worked. The auriferous detritus frequently contains shells, and bones of animals of existing species. The coarser materials of the drift are, chiefly fragments and rounded pebbles of the clay slates and grey sandstone on which it lies; but these are more or less mixed with pebbles and boulders of serpentine BRITISH NORTH AMERICAN COLONIES. »° | 97 and talcose slate. Sands containing specular, magnetic, and chromic iron ores, are also associated with this drift, as well as occasional rolled masses of white quartz, derived from the mountain chain bor- dering the district towards the north. The principal gold washings have been carried on on the Chaudiére, Du Loup, and Touffe des Pins rivers, and the results obtained have been, on the whole, satis- factory. During the season of 1851-2, fifteen men collected about 80 ounces, and one nugget weighing two ounces was picked up. On the Touffe des Pins a lump of four ounces in weight was found. From a personal inspection, made some years since, of the Canadian gold fields, we are inclined to believe that, in many localities, not only would the detritus, if worked on an extensive scale, pay a fair profit on the expenditure, but also that some of the quartz veins could be ° worked with considerable advantage.* Often, however, the thickness of the deposits is not sufficiently great, and the area locally occupied by the pay dirt is too limited to offer the requisite inducement for the installation of a regular system of sluicing. On the 16th March, 1865, an elaborate report was made by a Parliamentary Committee, after a searching investigation of the sub- ject, filling a closely-printed pamphlet of one hundred and twenty-six pages. A large number of witnesses, taken from all classes, were examined. Two or three extracts from this Report will show the character of the evidence elicited :— “In regard to the extent to which gold has been mined or discovered, your Committee have obtained very valuable and reliable evidence. The Gold Mining Inspector, Major de Bellefeuille, states the whole quantity of gold produced during the past season, in the Chaudiére Gold Mining Division, to be $116,000 ; and this, considering the comparatively small number of hands employed, must be regarded as a very handsome return, the average of the season being no less than $4 per day . per man. The Gold Mining Inspector’s Report, however, cannot be taken as representing the total quantity, as it comes only to the 30th of N ovember, since “In the report of a meeting of the present Chaudidre Gold Mining Association, dated St. Frangois, March 7th, 1866, accounts are given of fourteen different shafts now being sunk on quartz veins in the neighbourhood. One of these is twenty-four feet wide; another twenty ; another thirty; and in neither have the walls yet been found. The assays reported run from $75 to $150 per ton; but these are evidently results obtained from picked samples. Thirteen cwt. of ore, taken from one vein, crushed, and worked in New York by mill process, yielded at the rate of $40 to the ton. The whole expense of raising and working quartz at the mines, need not, it is said, exceed from $4 to $8 per ton. Machinery is also reported to have arrived at Quebec, and only to await the opening of the season to be erected. H SS. . GOLD. which period mining operations have been constantly carried on, and with satisfactory results, on the Gilbert. The greater portion of the gold, so far obtai has been taken from a small area on the Gilbert river, a few miles from its mo in the parish of St. Francis. It appears, however, that considerable quantities of - gold were obtained in various parts of the country, of which he was furnished with — ae no returns. Thus, for example, on the Stafford Brook, the evidence shows that — $2,000 were obtained, while his return shows only $300. “Tn regard to the winter operations carried on, on the Gilbert, the evidence of the miners is “highly important, as it was to some extent against their interest to give it. They have found hill tunnelling beneath the snow in winter, as profitable as alluvial washing i in summer. i ea “The total area occupied in Victoria by lower paleeozoic formations with their associated plutonic rocks, inclusive of tracts in which the overlying tertiary deposits do not exceed 300 feet, cannot be estimated at less than 30,000 square miles.” It is, however, to be observed, that although the ache rocks enclosing the auriferous quartz veins of Victoria appear to belong to a more ancient series than those in which gold quartz lodes are found in California, the drifts, constituting the deep dig- gings, seem, in both countries, to be almost, if not identically, of the same period, and are in each instance often capped by volcanic matter. In the report before referred to, Mr. Selwyn gives the fol- lowing description of the auriferous tertiary gravels of Victoria :— “The igneous rocks associated with them are strictly volcanic, and in no instance do they appear to be of older date than the close of the Miocene period. Their greatest development has taken place during the deposition of the Pliocene series, and in some instances it has evidently been continued toa period that could not be chrovalemaaig separated from the most recent geological events. “The exact period in the tertiary epoch when the gold drifts com: menced, is at present exceedingly doubtful. No beds are yet known in Victoria associated with, or forming a portion of such drifts; that contain fossil marine animals. Neither has any gold been obtained from beds below the known fossiliferous tertiary strata. The volcanic rocks, consisting chiefly of varieties of Trachytic Dolerites, Basalts, Trachytic Porphyries, &c., are in many districts interstratified, in contemporaneous layers, with the sands, clays, and gravels, of what are at present considered to be the oldest gold drifts, in which the lowest stratum, where the gold occurs, almost invariably consists of a water-worn quartz gravel. That there are gold drifts marking at least three distinct deposits, the results of successive upheavals and depressions, is quite certain; and it is now almost equally certain that the earliest of them was the result of the commencement of the oldest Pliocene period. In accordance with this view, they have been divided into Older Pliocene, Newer Pliocene, and Post-Pliocene deposits. These three stages sometimes occur: in the same locality without the intervention of any volcanic rocks, in which ¢ase- three bottoms or gold-bearing strata are found in one shaft, the last being always on the solid, unmoved paleozoic rock. About four hundred AUSTRALIA. 107 feet is the greatest known thickness of these Older Pliocene deposits including the associated volcanic rocks, and at this depth rich deposits of gold are found in them resting on the slopes, and in the hollows of what was once the old Plocene sea bed. The exact relations of: the gold-bearing drifts of the upper Tertiary periods to the marine Ter- tiary sands, clays, and limestones of the Miocene and Eocene series, is avery interesting point in Victorian geology not yet elucidated, and one which may have an important bearing on the probable extension of the deep gold leads of Ballarat and other gold fields. “In following the leads they are invariably found to deepen in the general direction of the existing surface water-shed. Thus, at Ballarat and other gold fields on the south side of the dividing range, they deepen in a southerly direction ; whilst at Clunes, Bendigo, &c., they invariably deepen in the opposite or northerly direction, and there seems no reason why they should not extend underneath a very large part of the extensive plains that stretch from the northern gold fields to the Murray, and from the southern flank of the dividing range to the sea-board, wherever the tertiary rocks forming these plains rest directly on the lower paleozoic strata.” It may here be observed that in Victoria there are, in addition to the great auriferous gravel beds generally referred to the Pliocene epoch, others of a comparatively non-auriferous character, which are found below them, and believed by Mr. Selwyn to belong to the Miocene period. In order to account for these older deposits being less auriferous than those occupying a higher position in the series, Mr. Selwyn has, we conceive, justly arrived at the conclusion, that there must be at least two distinct sets of quartz veins, that the older ones were formed prior to the Miocene period, and are comparatively barren, whilst the newer, formed after them, but before the Pliocene epoch, are productive. The former, therefore, will have furnished the materials for the barren Miocene gravels, whilst the disintegra- tion of the latter has afforded the detritus forming the productive Pliocene: deposits.* Below the basalt, the depth of auriferous allu- vium rarely exceeds from ten to twenty feet, more frequently not so much, and in many places the basaltic rock is known to repose, for a considerable distance, directly on the bare bed rock. In some parts of the country, not covered by basalt, such as China- man’s Flat, Maryborough and Bendigo, the thickness of the alluvium is known to be as much as from 130 to 140 feet; and a still more “ Mr. Selwyn’s Letter to the Victoria “ Mining Record,” February 22, 1866. 108 GOLD. remarkable instance has been exposed, where a shaft has been sunk to a depth of more than 400 feet, passing, from top to bottom, through a conglomerate formed of water-worn pebbles, and blue clay. At this place, the shaft, although not passing through eruptive matter, is sur- rounded by a volcanic country, and, up to January 1865, had not yet bottomed on the bed rock. In Australia, as in California, there are three distinct sources from which the supply of gold is directly obtained—viz., shallow placers, deep diggings, and veins of auriferous quartz.* In the early days of gold digging, the miner usually contented himself with excavating shallow pits in the clays and gravels, found in beds and gullies of the creeks, or with washing the soil from slopes of hills intersected by auriferous quartz veins. The methods of extracting gold were in all cases exceedingly primi- tive, and conducted with the aid of the smallest possible amount of plant and materials. When a light sandy earth had to be dealt with, it was either washed in the tin pan, or passed through a cradle; whilst if, on the contrary,-the soil was mixed with tenacious clay, it became necessary to puddle it before passing it through this simple machine. In order to effect this puddling, the auriferous material was thrown into a large tub, with a sufficient quantity of water, and continually stirred with a shovel until the clay became softened and held in suspension in water, which from time to time was run or drawn off, and a fresh supply added, until the sands and gravels remaining in the bottom had become sufficiently free of clay to admit of being cradled without difficulty. The residues, thrown away by the miners, who worked by this system, were necessarily * “Gold is now found to occur, not only in quartz veins and the alluvial deposits derived from these and the surrounding rocks, but also in the claystone itself, and, contrary to expectation, flat bands of auriferous quartz have been discovered in dykes of diorite which intersect the Upper Silurian or Lower Devonian rocks. Quartz of extraordinary richness has been obtained from these bands, and the new experience of the miner is leading him to look for gold in places heretofore entirely. neglected. It is probable that some time may be lost, and that his labours may not always be well directed or successful, but it is commendable that he should not be deterred from exploration by warnings and remonstrances, founded on surmises often baseless. If he had closely followed the older precepts, we should, at this moment, have been dependent for our yield of gold on the shallower alluviums, and the surface only of the veins of quartz. The miner is, however, prospecting the deeper tertiaries with well-grounded hopes of success, and some of the shafts which have been sunk to penetrate the veins are as deep as 590 feet. From these levels very rich quartz has been obtained.”—R. B. Smyth, Intercolonial Exhibition, 1866, p. 5. AUSTRALIA, 109 often very rich, and, after exposure to the disintegrating action of the atmosphere, were frequently reworked for gold with considerable profit. After a time, the small pits sunk in valleys and the bottoms of creeks, were carried down to the bed rock, where it was discovered that the principal part of the gold had usually accumulated. From the bottom of these, small drifts were extended in all directions, and the wash dirt carefully collected from the face of the bed rock, and brought to the surface for the purpose of being washed. The claims originally granted to the Australian miner were exceedingly limited, the dimensions of each being in most instances 10 feet by 10 feet, or 16 feet by 8 feet, and consequently this method of mining was only sufficiently advanced for operations conducted on such a restricted scale. These workings, however, in many cases crushed together, before the whole, or even the largest portion of the gold-bearing stratum had been removed; and hence one of the principal reasons why, in nearly all the more important gold fields, the alluvium has been repeatedly worked over with profitable results. This method of mining is still extensively practised in Victoria, but the puddling is now, in the majority of cases, effected either by horse or steam power. From the general scarcity of water in the auriferous districts of Australia, all operations connected with the process of gold washing require to be carried on with a view to the utmost economy of this indispensable agent, and consequently the hydraulic mining of California is almost unknown in the country, and even sluicing on a large scale is comparatively little practised. The deep diggings, on deposits of the Pliocene tertiary epoch, are in Victoria most frequently worked by means of shafts of greater or less depth, from which, when the bed rock has been reached, galleries are extended, and the pay dirt is removed, very much in the same way as coal is extracted from seams of that mineral. The pay dirt, on reaching the surface, is subjected to the operation of puddling, and the residue remaining in the machine subsequently washed for the gold it contains. This method of carrying on operations is not only expensive, but the working of deep leads, as the beds of these ancient watercourses are called in Australia, is frequently much impeded by the influx of water, and a relatively large proportion of the steam-power employed in the gold fields is utilised in pumping water from deep workings. The time necessary for sinking a shaft from the surface to the pay 110 GOLD. dirt may vary from a few months to one or more years, during the whole of which time no possible return can be made for the outlay expended ; and it is only after reaching the “ gutter,” that the harvest of the miner begins to be reaped. From a report, in 1861, of Mr. Davidson, one of the mining surveyors of Ballarat, it appears that the average yield of the celebrated leads, named the Golden Point, Inker- mann, Redan, and Nightingale, situated in his district, was from 10 dwt. to 24 oz. per cubic yard, and that the thickness of the pay dirt varied from one to twelve feet. Another mining surveyor states, that at the Waterloo Company’s claim, Ballarat, the total quantity of gold obtained was 6,750 oz., which, at 80s. per ounce, would amount to 27,0007. This company was occupied two years and one month in working out the claim, and the total expense of carrying out the works was 5,824/., thus leaving a clear profit of 21,176/, as the result of the operations. In some localities, as at Sandhurst, where the pay dirt is composed of water-worn pebbles, strongly bound together by ferruginous and silicious cements, it is crushed in an ordinary quartz mill, and the gold extracted by amalgamation in the usual way. The mining sur- veyors speak favourably in their reports of this system of treatment. These auriferous deposits of the Pliocene epoch are found at Bal- larat, Smythesdale, Creswick, Raglan, Ararat, Sandhurst, Indigo, near Beechworth, Maryborough, and various other localities in the province. Wherever the level of the ancient deposit is above that of the modern valleys, adit levels, or tunnels, are brought in on the leads, and the work is then conducted precisely, as if it had been reached by the sinking of perpendicular shafts. This method of mining has, however, many advantages over deep sinking, both with regard to the drainage of the workings, and transport of the stuff to be washed, and is invariably adopted wherever the conformation of the district admits of its introduction. In order to avoid the expense and loss of time involved in the drainage of long levels from the bottom of the shafts, to reach the deposits of pay dirt, it is now usual to explore the ground by means of bore-holes : and the true position of the auriferous channel having been thus approximately ascertained, the shaft is subsequently sunk in such a position as most conveniently to com- mand the lead, and reach it with the least possible time and expense. As far back as 1855, the attention of the local Government was directed to the necessity of supplying the gold fields with water, and in 1860 a first grant of 50,000/. was appropriated for that purpose AUSTRALIA, 111 this was followed, in 1861, by a further sum of 75,000/., for the extension of similar works. In the early days of the colony, the operations of quartz miners were exclusively confined to such outcrops as showed visible gold, and the rock being either broken by a hammer or pounded in a mortar, the gold was afterwards washed out in the ordinary tin pan. It was, however, soon found that the working of veins in depth could be prosecuted with advantage ; and at the present time, from one-fourth to one-third of the gold obtained in Victoria is the result of treating auriferous quartz. Whenever metamorphic slates appear at the sur- face, quartz veins are generally found, the general direction of the greater number being nearly north and south. . These veins vary in thickness, from a mere thread to forty or even fifty feet. The mag- netic bearings of the northerly and southerly veins are, with rare exceptions, confined within a variation of some 24°, and the strike of the easterly and westerly lodes, which are much less numerous, is nearly at right angles to them. The machinery usually employed in Australia for the treatment of auriferous quartz, is the ordinary stamping mill, which will be described in a subsequent chapter, each head, on an average, striking sixty blows per minute, and weighing seven cwt. About one horse power is consumed by each of these heads, a nominal ten-horse engine being most frequently attached to a battery of eight. The crushed quartz flowing from the stamping mill is conducted over blankets, mercurial riffles, amalgamated copper plates, and various arrangements similar to those employed in California and other gold-producing countries ; the Australian miners experience the same difficulty, else- where complained of, in separating gold from iron pyrites, and other metallic sulphides. The miners generally have, in common with those of other countries, come to the conclusion, that better results, with regard to profit, are to be obtained by crushing large quantities of only moderately rich stuff, with powerful and well-arranged machinery, than from treating a limited amount of very rich rock on a small scale. When, as at first, the cost of crushing and amalgamating a ton of quartz amounted to some 80s, a very small proportion of the auriferous veins of the colony could be treated with advantage ; but now that the total expense of raising and treating a ton of rock by steam-power has, under favourable circumstances, been reduced to about 16s, 4d., there are numerous reefs throughout the gold-mining region i i te GOLD. affording satisfactory results, and many others that would do the same, if extensively and judiciously worked. Many of the reefs have yielded quartz of extraordinary richness, as, for instance, one at Castlemaine, from which 266 oz. per ton were obtained, although this cannot be regarded as the average produce of the vein. Generally speaking, also, the yield of the quartz veins of Victoria has not been found to decrease in depth, and those which have been wrought below 500 feet from the surface have experienced no dimi- nution. in their produce. Quartz mining requires a considerable amount of capital, and is subject to all the usual fluctuations of mining enterprises, excepting, however, such as are influenced by the varying prices of metals; but, in spite of all its disadvantages, it has been found a highly remunerative occupation, and from the pro- ductiveness and extent of its reefs, it is certain that Victoria presents an attractive field for the investment of capital in this department of industry. Two of the most productive gold fields of Victoria havé been those of Ballarat and Bendigo. The gold field of Ballarat is the largest within the mining district of that name, and the centre of other outlying gold fields, among which are Clunes, Creswick, Smythe’s Egerton, Gordon, Steiglitz, Linton’s, Carnham, &c. The town of Ballarat is, with perhaps the exception of Sandhurst, the chief town of the district in which Bendigo is situated ; and Castle- maine, the chief town of the district of that name, the most important and largest within the six mining districts. The mining carried on in this district is, for the most part, of the deep alluvial class, the bed rock being seldom found at a less depth than 200 or 300 feet. Bendigo, the largest auriferous field of the Sandhurst district, was originally a shallow gold field, some of its famous gullies, yielding many ounces to the tub, having been scarcely a yard in depth. The soil from these has now, however, been all cleared away to the bed rock, and passed through the puddling machines, from whence it has issued in the form of a pasty sludge which may be seen in all direc- tions overflowing the surface of the county. In place of the placer diggings, which are at present, to a considerable extent, exhausted, the chief industry of Bendigo is now concentrated on its quartz mines, which extend over an area of some forty square miles. On the north side of the gold field, however, deep placer mining has been extensively carried on, where the bed rock was found to dip rapidly, and this extension of the Bendigo gold field is now heing extensively worked. AUSTRALIA. 115 It would be difficult to ascertain the average produce of the quartz crushed in the different reduction establishments in the colony since the commencement of quartz mining, but it appears from the Surveyor’s reports for 1860, that, in that year, 61,075 tons of rock from the Ballarat district yielded 38,378 oz. 6 dwt. of gold = 12 dwt. 13 gr. per ton. From the Beechworth mines 3,725 tons 16 cwt. of quartz gave 13,862 oz. 6 dwt. of gold = 3 oz. 14 dwt. 10 gr. per ton. The Sandhurst district afforded 2,678 tons 15 ewt. of quartz, yield- ing 6,361 oz. 8 dwt. of gold = 2 oz. 7 dwt. 12 gr. per ton. From the Maryborough district there were crushed 4,548 tons, pro- ducing 6,345 oz. 1 dwt. of gold = 1 oz. 7 dwt. 21 gr. per ton. ° The district of Castlemaine produced 13,301 tons 15 ewt., affording 14,955 oz. 11 dwt. of gold = 1 oz. 2 dwt. 11 gr. per ton. Ararat yielded 1,265 tons 10 ewt. of quartz, which gave 2,002 oz. 10 dwt. of gold = 1 oz. 11 dwt. 15 gr. per ton. In the same year there were 294 steam-engines; of the agere- gate horse-power of 4,137, employed in alluvial mining, and 417 engines of the aggregate power of 6,645 employed in quartz mining. There were, in addition, 138 water-wheels and 3,958 horse pud- dling machines in operation. The total approximate value of the mining plant in the colony was, at the same period, estimated at 1,299,303. The total number of steam-engines employed for gold-mining pur- poses at the end of 1864, was 888, of which 441 were used in alluvial, and 447 in quartz mining. In the following year there were 17,326 miners engaged in quartz mining, more than 2,000 distinct reefs had been discovered and named, and 491 steam-engines, equal to 8,606 horse-power, and 62 engines driven by water or horse power, were employed in quartz mines for crushing, winding, pumping, &c. On the 31st December, 1865, the number of leases in force in the different districts were as follows :—Ballarat, 88; Sandhurst, 318 ; Maryborough, 228 ; Castlemaine, 85 ; Beechworth, 300; Ararat, 24. There were 62,131 miners engaged in getting gold from the aurife- rous alluviums, and 4,131 machines of various kinds, 4,428 sluice boxes, and 648 sluices and toms used exclusively in this kind of mining. The quantities of gold obtained by the alluvial miners during three years were, as nearly as can be ascertained, as follows :— 1863, 1,133,567 oz.; 1864, 1,041,830 oz.; 1865, 1,093,801 oz.* * R. B. Smyth, International Exhibition, 1866, p. 24. I 114 GOLD. CLunes.—Port Phillip and Colonial Gold Mining Company.—This is the most — important and extensive quartz-mining enterprise in the colony. The extent of the claim is 160 acres, held on a lease for twenty-one years, from 1st January, 1857, at a royalty of 74 per cent. on the gross value of the gold raised. Operations were commenced by the present Company in 1857, and in the following year, Mr. Selwyn, the’Government Geologist, thus writes of its mines and establishments :—‘* Within the last twelve months, I have visited all the principal quartz reefs and crushing establishments on the northern and western gold fields, and the Port Phillip and Colonial, and Clunes Company, is the only one I have seen, of which it would be possible to say, that it leaves little to be desired, either as regards the system of working the mine, or the general arrangement and management of the machinery.” : The reefs worked are five in number, and are enclosed in a soft white and brown slaty sandstone, which, like the veins themselves, runs nearly north and south, and generally dips towards the east. With the exception of the overlying tabular basalt, no igneous rocks occur on the surface within three miles of these veins. The nearest granite is at Mount Beckworth, nine miles west of the Company’s property. Nearly three-fourths of the land held by the Company is occupied on the surface by a stratum of tabular basalt, and it is only in the south-western corner, where this rock has been removed by denudation, that the shales and sandstones, with their associated quartz veins, come to the surface. The following section, at the northern extremity of the Company’s property, Fig. 5, will serve to give a general idea of the formation of the county, and the relative positions of the different veins worked. ; Fia. 5. t rt . - on \\ WG . \W ¥ Ce . x | iH) | i \\ ~ \ AX : \ SN x BI OC AQR_EY ANN ; Quan \ \S SOQ \\ x \ AWNYAR . AUN ’ x : SRE LOW . 4 \ \ \ \\\ << CLUNES. (North Cross Section.) The extreme irregularity in the width of these veins in different portions of their course, will’ be at. once perceived by comparing the cross section at the southern boundary of the property, Fig. 6, with the foregoing. It will be remarked, that-in AUSTRALIA. | 115 this portion of the ground, the “Old Man Vein” is very much contracted, whilst the “Welcome Vein” has become entirely obliterated. This alternate swelling and pinching out of quartz veins appears to be peculiarly characteristic of lodes of auriferous quartz in all parts of the world. Fig. 6. ae VY Wy Vy] Ville “AY pike « as \\ ' WO BANS AY \ MINI SS VAAN nt \ \ Ww = v W PY 7 CLUNES, (South Oross Section.). The greatest depth to which this mine has been worked is 485 feet, and the tot al amount of quartz treated since the commencement of operations in 1857, to October 1866, has been 319,695 tons, yielding 185,488 oz. 0 dwt. 8 gr. of gold, giving an average produce of 11 dwt. 143 gr. per ton. We are indebted to Mr. C. H. Fielder, the secretary of the Company, for the information embodied in the following tables :— TABLE I. Return of Quartz crushed from June 1857 to October 186€, Amount} Net Amount of Gold Period. erished. produced, Average per Ton. Royalty. Total. = hee ae Tons. oz. dwt. -gr. oz. dwt. gr. Cae ese ds £ s. d. 1857 . 7Months.| 4,146] 6780 14. 8 1. 12 17 | 2,65011 1! 267644 6 (io oa ae 11,8204} 15,764 ~-9 .6 1 7 20 | 6,130 2 2] 61,301 3 5 1858-9. 12 _,, 17,542 18,16% 12 19 | 0 ye 6,202 15 8] 71,497 4 5 1859-60 12, 21,694 17,466 16 9g 16 0 | 5,135 14 4] 68,476 5 8 1860-1 12 ,, 32,258 | 24.396 6 3 15 2 | 7,178 3 2] 95,708 13 3 1861-2 .12 a3 34,236 22,012 Oe TL 12 20 6,479 18 4] 86,395 12 11 1862-8 12: .,,. 40,360 | 22,988 1 . 19 lH 9 | 6,850 4 5] 91,336 5 8 1863-4 12 a 44,149 17,611 8 0 8 0 5,227 1 9] 69,694 7 92 1864-5 12 ,, - |-54,413 20,596 15 12 7. 13 | 6074 3 0| 80,692 7 8 1865-6 12 _,, 59,576 19,775. 16 0 6 15 5,893 16 10) 78,584 19 1 mae ee ee 319,695 185,488 0 8 vee 11 144 |57,522 10 9/730,454 8 9 f. the 10ns O OLD. ‘ x ( s the monthly results of the operat rive oO Ss 1 table (11) joiner sub 116, The a 2. Dn Ss Sp ; — Oo oO = > oD . o a = ‘paureyqo sod ay) SunewmeSpeure pue Sunseor pure ‘sSurrey oy} Surysea Aq portoacoer st pos styy Jo uoysod W , we — e S e e Soa 919° |6 SL | 983} § § 61 O72) 9 OL | 20 Tia S | 116 7 |s85-€0 612‘ LIS |° et 293 b OSE P6918 ee 1 TLS 61. 3-9 | O IL) Ol Buh Pe hTEEL | Or SF POOR Ee) See ro “I ea 5 QzL'L|F% ST S| 08 | OLS | for | 9 9 | OLOT | 9 & | STE | 9FET |) O GG | GBIT | 8429 |) THOV Ba 6609 (7 USTs re et = £°9>) 6 LL [8a Tb fe 0%.) FIST | 0 £9.) 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THey S28 goL'F |0 OL e/ oor | #2 Z| os | 6 410 ST | eT /| Ite | 900t| O #9} Gt6 | Ak9g ||) IK ae BIG OO VOLS |= pale se a ns Ste [s}-66. 02 | 090 T | ee BP) O16 Ig9"F | Rake =e LILF 10 918 . C12 T6239). 12680 Lee CF 1 ee aba ‘ Se F He RII fg F ‘YMp °ZO ‘suo, +) Laas 3 ae ‘13 yap | ‘13 ‘yap | ‘ssouno|] ub ‘yao ‘SuOL “suo, “CO8L Ss n - aa ae |p ra Ss a a eee SP aR ES en re Su OD Cae ‘ ‘uog, rod |. ‘uoy, tad |. »kessy £q “f tas < ms OF ‘pop yo! 202d | WYord peywarl) a5 uoL Jed | sunrey ull ‘uog, aad | “pron jo |, AP ted | 109M Ted | odureg} s = S ‘speedo. ace e = ay OE a rte tins re Sane: pale ‘| gonporg | vonpotg poe, Tee: oS ZIV) dadorddd Sa S saqatg [e901 1) ra) ~~ & Se ME SO on oS. és 2 Fe "QOST aune 02 GOST hunnune wouf suLnzay PUD 7809 — + ute > & BS “ANVdNOO ONININ CIO9X TIVINOTON GNV dITIIHd JLYOd 3 22% = 5.20 TL WAV 2S Pe SaaS AUSTRALIA. 117 From estimates very carefully made by the Colonial Secretary of Mines, which, however, are not given as being absolutely correct, it appears that the total quantities of gold obtained in Victoria from quartz veins were, during the three years under- mentioned, as follows :— oz. dwt. Se NI ages) <<.) ns, je AOR AOD. 0 Ree re eo! 4 ve BOB CIBY S Ree ee le by ade sade 200,000: 0 The following particulars relative to a few of the principal mining operations in the colony have been collected from the files of Dicker’s Mining Record. BaLitarat.—The following workings in this locality are classed as alluvial :— Cosmopolitan.—Commenced 1857 ; claim 880 feet on the gutter; basaltic rock 112 feet in thickness; total length of drivages, 2,500 feet; stuff puddled and washed up daily. This undertaking had produced 38,249 oz. 4 dwt. 19 gr. of gold, of the value of 152,442/., and paid dividends to the amount of 125,454. up to November 19th, 1864. United Extended Band of Hope.—Extent of claim, 36,040 feet ; commenced in 1856, and had yielded gold to the value of 259,547/. ; of which amount 147,2001. had been paid in dividends up to 31st December, 1865. Defiance Company.— Commenced, 1856, and had afforded 20,197 oz. 18 dwt. of gold of the value of 81,1027. ; out of which 66,483/. had been paid in dividends up to December 24th, 1864. Koh-i-Noor. — Commenced, 1857; produce, 60,332 oz.; value, 241,2331. ; dividends paid, 176,080/., up to December 6th, 1864. Prince of Wales.—Commenced, February 1857; gold produced, 22,912 oz. 11 dwt. 19 gr. ; value, 90,735/. ; dividends paid, 51,552/., up to December 10th, 1864. Alston and Weardale.—Commenced, July 1858; gold produced, 2,585 oz. 15 dwt. 3 gr. ; value, 10,4517. ; dividends paid, 4,884/., up to August 1864. Great Extended.—Commenced, 1857 ; amount of gold produced, 82,754 oz. 9 dwt. 14 gr. ; value, 325,9671. ; dividends paid, 274,4501., up to December 4th, 1864. Buninyrone.—Buninyong Mining Company.—Alluvial. Commenced, November 1857 ; gold produced, 43,175 oz. 16 dwt. 22 gr. ; value, 172,6951. ; dividends paid, 88,0071., previous to November 26th, 1864. Day.esrorp.—New Wombat Hill.—Alluvial; commenced April 1861; gold produced, 14,942 oz. 14 dwt. 19 gr. ; value, 58,0591. ; dividends paid, 38,4001. up to November 5th, 1864. Benpico.—Catherine Reef United.—Quartz; claim, 501 yards, held under a lease from the Government ; vein 4 feet wide, with strike 23° west of north, and a dip to the east ; commenced, March 1861 ; gold produced, 24,930 oz. 15 dwt. 12 gr.; value, 95,7841. ; dividends paid, 29,7351. previous to December 17th, 1864. SCARSDALE.— A vonclift.— Alluvial ; area of claim, 133 acres; depth of basalt, 84 feet ; two gutters running parallel ; depth of wash dirt, 4} feet ; gold produced, 4,272 oz. 14 dwt. 12 gr.; value, 17,0901. ; dividends paid, 4,0001. up to September 1864. Harry Vauiey.— British Gold Mining Company.—Allwvial ; extent of elaim, 118 GOLD. 50 acres; held under a lease from the Government ; the gutter is 30 feet in width, and the depth of the wash dirt, about 3 feet ; commenced in July 1860; produce of gold, 17,591 oz. 6 dwt. 1 gr.; value, 70,126/.; dividends paid, 40,8001. up to March 4th, 1866. Try ohn Gold Mining Company.—Alluvial ; commenced, Septenibes 1859 ; extent of claim, 49 acres ; held under a lease from the Crown ; wash dirt from 2 ss 3 feet in Pekan: ; gold produced, 6,153 oz. 7 dwt. 8 gr. ; value, 24,5351.; divi- dends paid, 9,802. n to December 10th, 1864. Cleft in the Rock.—Alluvial ; comneneet November 1859 ; extent of concession, 50 acres. held under a lease from the Crown ; main lead bearing north and south ; thickness of pay dirt, from 2'to 7 feet ; produce of gold, 3,848 oz. 14-dwt. 11 gr. ; value, 15,2871. ; ie paid, 5, 9601, up to December 12th, 1864, : Woon’ S Por, —Alps Great Chiival Gold Mining Compara —Quartz; com- menced, July 1863 ; produced 27,500 oz. of gold ; value, 92,8121. up to July 1865. Hope Mining pou. Ga ; commenced, July 1863 ; produce of gold 8,732 oz. 3dwt. ; value, 27,032/. up to July 1865. By an Act for the better management of the gold fields of Victoria passed by the Colonial Parliament in 1857, the whole of the aurife- rous region was divided into the six following mining districts, each called after its chief gold field, or rather after the chief town in its most important gold field :—Ballarat, Castlemaine, Sandhurst, Mary- borough, Beechworth, and Ararat; but this division is entirely arbi- trary, and totally unconnected with any geographical or geological features of the country. The only connecting link between the Colonial Government and the gold fields, is the Warden, whose duty it is to attend to the settlement of small disputes connected with the gold-mining interests ; to report on the advisability of granting leases of mineral lands, and to draw up periodical reports relative to the state of the gold fields in his district. Each gold field, and sometimes each division of a gold field, when it is a large one, has its own Warden, whose correspondence with the Government passes through the hands of the Chief Warden. Each district has its own Mining Board, of which the members are chosen by ballot by the gold miners, and which arranges all gold-mining questions within its jurisdiction. Kach member receives a small allowance for his attendance at the board, and holds office during three years, at the expiration of which he.is eligible for re-election. A Court of Mines is also established within each mining district, before which come all disputes above the adjudication of the Chief Warden. The judges of these courts are independent of the Colonial Government, and hold office quamdiu se bene gesserint. From the decisions of the judges of the Court of Mines there is a power of appeal to the Supreme Court of. the Colony. 3 | AUSTRALIA. 119 The following amounts of gold have been exported from the Colony of Victoria since 1850: — PERIOD. QUANTITY. ; | VALUE. | Se reaptiay vee acme ne ae 1851 . 445;137... .3...12 580,548 12 0 | | 1852. 1,988,526 10 13 7,954,106 0 0 | 1853 . 2,497,723. 15 16 9,990,895 0 0 || | 1854.. 2,144,699 9°. 19 ~ | 8,578,797 16 0 | 1855. 2,575,745 4 17 | — 10,302,980.16. 0 | 1856 . 2,985,695 17° 0 «| * 11,942,783 8° 0 ! - 1857 . Brerbes 148) 0) 2 110460. 113 Teo 1858 . 2,555,263 0 0 10,221,052 0 O 1859 . 2,280,525 14 0 9,122,102 16 0. | 1860. 2,128,466 11 0.. 8,513,866 -40. | 1861 . 1,978,864 13° 0 7,915,458212 7.0 [2 1862 . 1,662,448 18 0 6,649,795 12 0 1863 . 1,627,066 O @ 6,508,264 0 0 | 1864 . 1,545,449 15 0 6,181,799 0 O | 1865. 1,545,450 Oo 0 6,181,800 0 0 30,422,591 05 fa 690,363 8 0 | | In addition to the above amounts, exported direct from the colony, 1,691,150 oz. of gold, produced in Victoria, are known to have been shipped through the Customs of New South Wales, Tasmania, and South Australia, besides a large amount (estimated at 2,250,000 oz.) that left the country in private hands. The total exports of the colony, from the commencement of gold- mining operations to the end of 1865, will therefore be nearly as follows :— OZ. dwt. gr. 30,422,591 0 1,691,150 0 0 2,250,000. 0 O ; Total 34,363,741 0 0 The total value of the gold exported from the colony, up to the end of 1865, will consequently be nearly 138,000,000. exclusive of that absorbed by the currency, &c. of the country.* Returned by Victoria Custom House Not returned S - a Taken by Private Hands * The Colonial Secretary of Mines estimates the quantity of gold produced in the colony, from the first discovery of the gold fields, to the 31st December, 1865, at 30,998,071 \0z. ; value £123,992,284 ; but no allowance is made by him for the gold which had been sent off privately, or for the amount used and manufeetured in the colony, 120 GOLD. New South Watzs.—Although the first practical discovery of gold was made in New South Wales, some weeks previous to its being found in Victoria, its total produce of the precious metal has been far less considerable than that of the sister colony. The general descrip- tion of the gold fields of Victoria is equally applicable to those of New South Wales, but we are without any very definite information relating to the different workings in the latter colony, which are, however, much less numerous and extensive than those of Victoria. Among the principal mining districts of New South Wales may be mentioned Abercrombie, Summerhill, Ophir, Turon, Tamworth, &c. &c. The pro- duce of gold from New South Wales up to the close of 1860, amounted to about 8,000,0002., whilst Victoria had exported gold to the value of nearly 90,000,000/. during the same period. According to the Government returns, entitled “Statistical Abstract for the several Colonial and other Possessions of the United Kingdom, 1866,” the export of coined and uncoined es from this colony, up to Sil had been nearly as follows :-— PERIOD. | QUANTITY. VALUE. 3 } | | | L | OZ. & Fo) Raa ee eee 144,120 470,836 IBBe rey a. he, 818,751 2,660,945 1858 vices ee 548,152 1,781,272 1BG4: ier een 237,910 773,209 1Spbs ie ko 64,384 209,250 LBBB sre es 46,999 156,151 1867; ba. epee Gad 1,101,448 LOG! secs et 443,462 1,773,851 LRG ere kee 0 427,558 1,704,774 SOOM oot 472,886 1,878,588 Toh Sacre Nae 507,021 2,010,263 1862 fake dys 741,055 2,984,269 | L863 Seni s 593,699 2,362,054 Obs unk e o als gees 2,952,471 6,063,576 22,819,381 Although we have not been able to obtain the same amount of statistical information with reference to this colony, as is to be procured ee AUSTRALIA. . 121 with regard to Victoria, it is probable that a very large proportion of the gold exported from New South Wales is the produce of other portions of the Australian Continent. The establishment of a mint at. Sydney has naturally caused large quantities of gold to be imported, for the purpose of being converted into coin, but the total produce of the gold fields of New South Wales, since their discovery in 1851, is estimated at only 4,000,000 oz., and the present annual yield at about 320,000 oz. SoutH AUSTRALIA AND TASMANIA also annually produce a certain amount of gold, but the quantity is comparatively small, since, from 1851 to the close of 1860, the total weight exported, including the exports from New Zealand, was represented by a money value of 374,0002., of which New Zealand is supposed to have contributed more than one-half. The amounts and value of the gold exported from South Australia and Tasmania, including New Zealand, from the discovery of gold in those countries to the end of 1860, were nearly as follows :— PERIOD. QUANTITY. VALUE. OZ. £ | top a 5,250 21,000 | Das ae a 5,250 | 21,000 | Tete eee. 5,250 -gn00ee | 4] TORO MIS 0.00 5,250 21,000 LEAGE F802) it: 5,250 | 21,000 | DAR ee aye | 40S 15,689 |: 62,556 | LOBES Ape tes 5 18,680 | 74,720 | ee oe 16,431 | 65,724 | eRe ok 4 oe 16,500 | 66,000 93,500 * 374,000 (JUEENSLAND is likewise, to a certain extent, a gold-producing country, and affords a small yearly yield of the precious metal, but we have been unable to procure any returns of its annual produc- tion. According to Dicker’s Mining Record of 17th April, 1866, there is but one quartz-crushing establishment in that colony, and only 123 GOLD. one quartz-mining company now at work. This association: 1 holds the lease of three quartz reefs from the Crown. The extent of the ground held is 400 yards in length, on the Ping : of each reef, by a width of 200 yards. The Alexander Reef is twenty- two miles from Gladstone, on the water-shed of the Boyne River. A crushing had been made of 400 tons, which paid satisfactorily. There was only one very indifferent mill of 10 horse-power in the country; The charge for crushing was 25s. per ton. On this reef there were five shafts, varying in depth from 80 to 100 feet ; the thickness of the vein varies from two to four feet. The reef forming the second lease is on Bell’s Run, twelve miles from Gladstone, on the water-shed of the Caliope. There had been six shafts sunk, varying in depth from 50 to 70 feet, and the thickness of the lode is from three to eight feet. The proprietors had sent two tons to Sydney to be crushed, but the result had not been announced at the date of the despatch leaving the colony. The third lease is on a quartz reef, on the range dividing the waters of the Boyne from the Caliope. Not much, however, had been done here up to the spring of 1866, although two shafts were then in course of sinking. NEw ZEALAND. - The first authentic discovery of gold in New Zealand was made at. Massacre Bay in 1842, by an exploring party under Captain Wake- field, but did not at the time attract much attention. No further discoveries of this metal were announced until 1852, but in that year gold was almost simultaneously found in the Provinces of Auckland and Otago, and, from the important results which had then been obtained from the Australian gold fields, excited a con- siderable amount of public attention. The Auckland discovery was made at Coromandel, but only about 1,100 ounces of gold were obtained, and the district was shortly afterwards abandoned. In 1856, attention was called by the Surveyor-General of New Zealand to the existence of gold in the sands and gravels of the Mataura River, and in the same year discoveries were made at Motaeka, in the Province’of Nelson ; whilst inthe following year, the gold field at Aorore, Massacre Bay, on came into notice. A rush of the popu- lation: to the gold regions was the result of these discoveries, and about a thousand persons were for some time employed in the NEW ZEALAND. 133 diggings with varying success; but the severity of the season, and want of practicable roads, soon led to the discouragement of a large number of the miners. The exports from this district, up to the end of 1858, amounted to 16;473 ounces of gold. The richest diggings on the Aorore gold field were those on the Slate River, which takes its rise in the Anatoki Range, and afterwards falls into the Aorore. This river has high and precipitous banks, composed of granite, slate, and quartz; the gold being found, associated with osmiridium, in a yellow sand met with in the bed of the stream. | In ‘the latter part of 1857, the existence of gold in aa was made known; and the Sub-Assistant Surveyor, Mr. Gillies, and party, found gold in a creek running between the Waikioi and Makerewa Bush, and emptying itself into the Makerewa. About the same period, Mr. Garvie, another Sub-Assistant Surveyor, found traces of gold in many of the sands and gravels of the south-eastern district of the Province. In March 1858, Mr. Garvie brought into Dunedin the first important specimens, which were obtained by Mr. Buchanan from the river beach of the Dunstan gorge, which four years later proved so highly remunerative to two old Californian miners, named Hartley and Reilly, and which ultimately led to the development of the most extensive gold field in the Province. In the same year, gold was discovered in the surface gravel near the mouth of the Tuapika River, and also in the River TLindis. Further discoveries continued to be made in the Province of N leon and in 1859 some nuggets, weighing from two to nine ounces, were found in the Rocky River. Gold was found in considerable quantities in the River Lindis in March 1861, in the form of water-worn nuggets of the size of beans as also, in a finer state of division, in the Kakanui, near Moeraki. In June of the same year, a discovery was made from which may be dated the importance of Otago as a gold- producing. country. Mr. Gabriel Read was led by curiosity to attempt the verification of the reported presence of gold in that district, and in the course of his expedition examined the ravines and tributaries of the Waitahuna and Tuapika rivers. With a tin dish and a knife for his only tools, he'collected seven ounces of gold in about ten hours, and ascertained the existence of the preciotis metal in many of the creeks and gullies: These, discoveries of Mr. Read were shortly afterwards confirmed by the results obtained by other explorers, and caused a ereat rush to the district, where discoveries follow ed each other in rapid succession; 124 GOLD. fully establishing the fact of the existence of a valuable and extensive gold ‘field. Early in 1862, fresh discoveries were made at Coromandel, where a large number of miners congregated, and several companies were organised for working quartz veins. The gold diggings on the western coast of Nelson also gave promise of being highly productive, and some very large prospects were obtained. In the month of August a discovery was made in the Province of Otago which exceeded in importance those of the previous year. In February, two men, who had been miners in California, started on a prospecting tour up the Molyneux River, and found gold so readily, that, to use their own words, “they had nothing to do but to set the cradle on the edge of the river and keep it going from morning till night, as one man could get rich wash dirt to feed the cradle as fast as the other could wash it.”. These men, Hartley and Reilly, as the result of three months’ work, brought into Dunedin 87 lbs. of gold, and received from the Provincial Government a bonus of 2,000. for making known the locality from which it had been obtained. In the latter part of 1862 and the beginning of 1863, the area of the gold field of Otago was much extended, and in the latter year large amounts of gold were obtained, and immense areas of auriferous ground opened up, on the Wakatipu Lake and its tribu- taries. Towards the latter part of 1863, further and important dis- coverles were made on the western coast of Nelson, and in the early part of the following year the Matakitaki Diggings, in the same pro- vince, came into considerable notice. In April 1864, the first discovery of gold was made in the Pro- vince of Marlborough, in the River Wakamarina and its vicinity ; but disastrous floods, and the impenetrable nature of the country, have prevented the rapid development of this gold field. During the same year, gold was obtained from the banks of the Teremakau River to the west. of Canterbury, and various other localities along the coast. In the year 1865, another very important discovery of gold was made in the Hokitika River, on the west coast of Canterbury, the yield from which, up to the present time, has been very considerable ; and as further discoveries are being made in the district, it is probable that this river, and the district around it, will turn out to be a rich and important gold field. Gold mining is now being successfully carried on at Coromandel in the Province of Auckland, at Massacre NEW ZEALAND. 12% Bay, and on the Buller, Lyell, Wangapeka, and other western streams in the Province of Nelson; in the Grey, Teremakau, and Hokitika rivers, and over a large extent of the western coast of the Province of Canterbury, as well as over a vast area in the Province of Otago. In New Zealand, as in all other gold-bearing countries, the zones of clay slate and mica slate appear to be the original sources from which the supply of the precious metal has been chiefly derived, but the largest portion .of that at present obtained has been procured from workings in the alluviums, some of which, like those of California and Australia, extend under a capping of volcanic rock. The geological age of the auriferous drifts of New Zealand is probably that of the gold-bearing alluviums of Australia, although this does not appear to have been as yet distinctly proved. Quartz mining is as yet in its infancy in the colony, but several promising reefs have been opened, and are expected to afford satis- factory returns. The most important quartz mines at present known are at Waipori. A large proportion of the gold produced in New Zealand is obtained by sluicing, and so favourable have been the results of this class of mining, that it may be fairly anticipated, that the Province of Otago will be a large gold-producing country for many years to come. River mining is profitably followed in various parts of the country, particularly in the Wakatipu district, and in the beds of the Molyneux and neighbouring streams. As these deposits gradually become exhausted, the attention of miners will, doubtless, be more exclusively directed to the thicker formations of auriferous drift. The following statistics relative to the gold production have been compiled from official sources : * — TABLE I. AMOUNT OF GOLD EXPORTED. OZ. dwt. gr. . 1861-1862, Ist August to 3lst July . . . . 457,239 10 1862-1863 ‘ # uy 514,385 17 0 1863-1864 o : ps, beset ed dds 0B 1th atgty ¢ 0 1864-1865 s 3lst March. . . . 231,010. 11 = 0 Total quantity exported from Otago. . 1,699,667 7 6 * New Zealand Exhibition, 1865, Reports and Awards of Jurors. 126 . GOLD. In addition to the above, 63,970 oz. of gold, the produce of: the gold fields of Otago, were exported from other ports in the colony, making the grand total exported 1,763,637 oz. 7 dwt. 6 gr, value 7,054,544, ae ie TABLE ILI. Showing the quantity and value of gold from the gold fields in each Island, and the whole of New Zealand, exported from the Colony, from 1st April 1857 to 31st December 1864.* | i ea ‘ Total éxported from . 7 From 1st. April 1857 to : Produce of. During 1864. fi New Zealand, to : 31st December 1863. 31st Dec. 1864.. * —<—- Fe e —— ; OZ. & OZ. £ OZ. £ North Island 3:4 fe 3,448 10,552) 6,076 19,323) ~ 9,524! — 29,875) South Island . . . .|476,723/1,847,295/1,263,112/4,894,560/1,739,835 6,741,855 1,857,847) 1,269,188/4,913,883| 1,749,359 6,771,730 | Total from New Zealand |480,171 The following table gives the approximate yields, in lbs. troy, of the principal gold-producing countries at the commencement of the present century, and for the years 1850, 1860, and 1865. In cases where the returns for the year indicated could not be obtained, the produce for the nearest years, for which they could be procured, has been substituted. The quoted produce of the mines of the United States and of the British Possessions, may, however, be regarded in each instance as being nearly correct, except that the return for California and the neighbouring States and Territories for 1865, is probably somewhat under the truth, since it is exceedingly difficult to ascertain the precise yields of Idaho, Montana, Colorado, and some other outlying districts. After each absolute sum is given its relative weight, in comparison with the grand total produced throughout the world :— “ The returns state : “The value has been calculated on the uniform estimated rate of 31. 17s. 6d. per oz., with the exception of the gold from the North Island, for which the ascertained value has been allowed. This table has been compiled from the Monthly Returns of Gold Exported, which do not in all cases exactly correspond with the Quarterly Trade Returns of Exports from the Colony, as furnished by the collectors of their respective ports, from which Table I, was constructed.” 3 ~ STATISTICS. yar TABLE SHOWING APPROXIMATE PRODUCTION OF THE PRINCIPAL GOLD FIELDS OF THE WORLD. 1800. 1850. 1860. 1865. Ibs. troy. ratio lbs. troy. ratio lbs. troy. ratio - lbs. troy. Faldo per cent. per cent. per cent. per cent. Russian Empire . .| 1,440 2°7 65,600 19°0 66,000 Das 69,500 12°4 ‘Austrian Empire 5,600 16 * 5,500 10 =| - 56,500 10 and 3,500 ° 6°5 Rest of Europe ve ah 350 ak a76 Southern Asia. .. 10,000 18°5 25,000 ee 25 000 4 25,000 4°5 ates A. G00 12 4,000 Vl 4,000 0-7 | 4,000 0-7 Com oh ew 4) 7,500 13°38) | : Belivialse. . . » 2p 1,600 3°0 IbemMiasea = 3 sx ah) 2,400 4°4 «| 34,000 =e} 34,000 59 34,000 61 New Granada. . . | 12,600 23°4 : | Brazil . . . . .| 10,000 | 185 | Beemer ee toe., oh £900. 4. 9” 8-0 California & neigh- bouring States &')... | Pe 208,000 | 60:2 | 187,000} 31:9 | 210,000} © 3775 Territories Rest of United States see 2% 2,950 09 1,020 0:2 140 Nova Scotia . .. ee - ae na 6 = 2,072 0-4 British Columbia. . ve | i eee 7 20,000 3-4 11,600 2°1 a ene ar oat eee 217,500 | 87:0 | 156,000| 27°9 ho a cre ae < 25,000 4°3 41,400 74 | 53,940 100 345,250 100 585,370 100 559,587 100 * The yields of the different members of this group vary considerably from year to year, but the aggregate produce is believed to remain tolerably constant. e CHAPTER VIII. GOLD WASHING IN CALIFORNIA AND AUSTRALIA. PLACER MINING—-THE PAN—ROCKER—LONG TOM—PUDDLING BOX—SLUICE—RIVER MINING—-BEACH MINING—-WATER SUPPLY—EUREKA CANAL—HYDRAULIC MINING —AMOUNT OF WATER REQUIRED—COST OF WATER, AND METHOD OF MEASURE- MENT—DRY WASHING. GOLD mines may be divided into two distinct classes, viz., Placer Mines, in which the metal is found, in a more or less water-worn condition, embedded in earth, clay, sand, or gravel; and Quartz, or Vein Mines, in which gold is met with disseminated in its original gangue, or matrix. In the former, the gold-producing material is called “pay dirt,” which, on being subjected to the action of water, becomes disintegrated, and the lighter portions are mechanically carried off, whilst the gold, from its greater specific gravity, remains behind. In the latter, on the contrary, after first obtaining the rock by the ordinary operations of mining, as practised with regard to other metals, it has to be reduced by mechanical means to the state of a finely-divided powder, before the associated gold can be collected, either by washing or amal- gamation. : The amount of skill and capital necessary for the successful pro-. secution of placer mining, is usually less than is requisite for carry- ing on quartz mining, on a remunerative scale; and as placer mines are generally those to which attention is first directed in a new country, and from which remunerative returns are most readily ob- tained, we shall, in the first place, describe the processes employed for extracting gold from the various alluvial deposits, and subse- quently pass on to the consideration of quartz mining, and the extraction of the precious metal from the veinstone constituting its original matrix. Water is the great agent hy the aid of which placer mining is carried on: with a large supply, the operations of the miner can be. cheaply and rapidly conducted; but without water, or with only a ~ ale GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 129 limited amount, a claim that would otherwise have been highly pro- ductive, may either become valueless, or only capable of affording very irregular returns. Placer mines are of two distinct classes, the shallow and the deep ; shallow, or surface diggings, are generally found in the beds of ravines or gullies, on the bars and in the beds of modern rivers, and on shallow — flats. In the latter, the pay dirt is often found at great depths from the surface, and is not unfrequently covered by thick beds of lava, or voleanic ash, as in the case of the deposits under Table Mountain, Tuolumne County, and near Nevada City, California. In the deeper placers, the auriferous drifts are reached either by shafts of considerable depth, or by means of levels, or tunnels, driven in from some neighbouring valley. The pay dirt, after being thus extracted, is conveyed to the surface, in order that it may undergo the usual process of washing. In other instances, hydraulic mining is resorted to, in which case jets of water, under great pressure, obtained from a high column, are directed against the deposits of sand and gravel, which are thus not only disintegrated, but finally carried away by the current. This is the most economical and expeditious method of working placer mines, when a sufficient supply and pressure of water,can be obtained, and there is also enough declivity below the auriferous beds to allow of the resulting detritus being readily dis- posed of. The pay dirt is almost invariably covered by various layers of barren clay and sand, which are, in the shallow diggings, removed by the use of the pick and shovel; but, in hydraulic workings, the whole is washed away by the force of a stream of water playing against it, and any particles of gold which it may contain are caught in the sluices through which the lighter materials pass. In many of the deep placers, after reaching the pay dirt by means of shafts or tunnels, it is extracted by a system of levels and headings, not unlike those employed for working a coal seam in this country. In California, besides classifying the placer mines as shallow and cleep, they are again subdivided into hill, bench, flat, bar, gulch, and river diggings, with reference to their topographical position as regards the surrounding country. Hill diggings are in the sides of hills ; bench diggings are on narrow benches on the declivities of hills, and above the level of existing rivers; flat diggings are situated on flats or small plains; bar diggings are usually in collections of sand and gravel, on the sides of streams, and, under ordinary circum- stances, above the surface of the water; gulch claims are found in y 130 ’ GOLD. ravines and gullies, through which no water passes, except in times of extraordinary floods; river diggings occur in the bottoms of rivers, and can only be worked after diverting the water from its original — channel. Placer claims are likewise spoken of as sluice, hydraulic, and tunnel claims, dry diggings, &c., in accordance with the means employed for reaching the auriferous deposits, and the methods adopted for the separation and collection of gold. In the early days of Californian and Australian gold mining, when paying diggings could.generally be * found near the surface, and before the large deposits of pay dirt lying at great depths below the ground had been discovered, the greater portion of the gold produced was obtained from shallow workings. These have now, to a great extent, become exhausted, and in Australia - shafts are sunk to the older deposits, whilst in California enormous aqueducts have been constructed, and hydraulic mining is extensively introduced. In both countries, therefore, at the present time, the greater portion of the gold obtained is the result of deep mining, the shallow placers being generally abandoned to the Chinamen, who are satisfied to wash over the dirt which has been already passed through the machines, or has escaped the attention of the ordinary miner.. : The object of the miner is generally to obtain the largest quantity of gold in the shortest possible time, and with the least amount of labour and expense, rather than to extract the total amount contained in the . material on which he operates ; and, consequently, without taking into consideration the necessary loss incident to the imperfect nature of the appliances employed, his refuse will naturally retain a certain propor- tion of the gold originally present. The falling abroad, however, of lumps of clay, by the action of the weather, constantly exposes fresh particles of the precious metal, and from this cause the residues frequently afford an amount of gold that could not have been other- wise obtained from them. Many contrivances have been introduced with a view to obtaining the whole, or a large proportion, of the gold present in the pay dirt, but, in the majority of instances, the result has been a failure; and if an increase of yield has sometimes been obtained, the additional gold extracted has frequently been more than compensated for by the extra expense entailed. Whilst the supply of shallow auriferous dirt was sufficient to furnish employment for the whole labouring population, the gold produced was almost exclusively obtained either by solitary diggers, or by small private companies of working men, whose capital consisted rather in GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 131 their united strength, than in an accumulation of money. Things went on in this way until the richer and more easily-worked alluviums had become partially exhausted ; when it was found that to carry on successfully the deeper diggings, combinations on a somewhat more extensive scale became necessary, and that capital and intelligence, as well as strength and endurance, were required by the gold miner. While there was no difficulty in finding shallow claims that would pay from 25s. to 30s. per day to the hand, it was almost impossible to obtain the labour necessary to carry on either deep digging or quartz mining with any chance of success ; but when these began to be worked out, this difficulty gradually disappeared, and attention became directed to operations on a more extensive scale, generally conducted either at the expense of a co-operative company, or joint- stock association. In this way, the usages and exigencies of a newly- discovered gold region rapidly change and become more assimilated to those of more commercial and longer established communities, A lucky miner becomes a capitalist, and in the gold regions, as in all other places, money commands labour, and large operations are com- menced, often to the doubtful advantage of the speculators, but to the manifest benefit of the general community. Having thus briefly alluded to the general conditions of recently discovered gold regions, we will proceed to describe the various appliances employed for the separation of gold from the different earthy materials with which it is associated, beginning by the cheaper and more simple, and afterwards treating of the more complicated and efficient arrangements now generally employed. Lhe Pan.—This is the indispensable companion of the gold miner, and is used by him in all branches of his business, either for washing, or as a receptacle for gold,-amalgam, or rich dirt.- It is made either of stiff tin plate, or of thin sheet iron, and is at bottom about fourteen inches in diameter. A sheet iron pan is generally to be preferred to one made of tin plate, not only because it is stronger, but also because it is unattacked by mercury, if brought in contact with that metal. The top is from three to four inches wider than the bottom, and consequently the sides, which are about five inches in depth, and strengthened at the edge by a thick wire, have a considerable incli- nation outwards. In order to wash with the pan, it is first about two- thirds filled with dirt, and then placed in a water-hole, which should not be more than about a foot in depth, in order that the vessel may rest on the bottom, whilst the miner stirs up its contents with his K 2 132 - SGOLD. hands. If the water be too deep for this, the pan may be held in one hand, and stirred with the other, but it is more convenient, and less tiresome, to be enabled to let it rest on the bottom. The dirt having been placed in the pan, and the pan itself filled with water, the miner inserts his hands into it, and raises and stirs the dirt, so as to make every part of it thoroughly wet. Having done this, he now takes the pan in his hands, holding it by the two opposite sides, but somewhat behind its greatest diameter; and raising slightly the part which is towards him, and consequently depressing the outer edge, he commences to shake it from side to side in such a way that all the dirt is beneath the surface of the water, and at the same time, by a sort of circular motion, he allows a small portion of it to pass over the edge at each oscillation. The earthy particles, together with the fine sand, soon become suspended in water, and gradually pass over the side in the form of thin mud, whilst the gold, the tough clay, and large stones remain behind. The stones collect on the top of the sand and clay, and are scraped off with the fingers, while the lumps of clay are rubbed between the hands, and thus prepared for being taken up by water during the next washing. The process is thus continued, the pan being gradually — raised in the water, and its outer edge further depressed, until the greater portion of the clay and stones have been removed, and the gold remains, together with a little earthy matter and black sand. At this stage of the operation, the pan is nearly filled with water, and after being removed from the pool in which the washing has been hitherto conducted, is shaken, so as to get the last portions of clayey matter in suspension, and the water carefully poured off, as shown mene y, | The outer edge of the pan only is now immersed in water, and a further portion of the clayey matter removed by careful washing, leaving the gold, and a small quantity of heavy titaniferous iron sand, in the angle formed between the bottom and side. This black sand, which is mixed with the finer particles of gold, is so heavy that it cannot be separated from the metal by washing, but can, to a great extent, be removed by a simple process of blowing. In order to do this, it is allowed to dry, and a small quantity of it placed in a blower, which is a sort of dish, or shallow tin scoop, open at. one end. The miner now holds the blower with the open end from him, and with his mouth directs a gentle stream of air along the surface of the mixture of gold and fine sand, taking care so to regulate its force as o« GOLD WASHING. IN CALIFORNIA AND AUSTRALIA. 13 to remove the latter without causing a loss to the former. To effect this, the blower must be gently shaken, so as to change the position 2 of the particles, and bring them all, in turn, under the influence of WASHING WITH PAN. the current of air; and although the gold cannot be thoroughly cleansed in this way, any remaining particles are readily removed by a magnet. The pan is always employed for washing up the rich dirt which collects in the cradle and sluice heads, and is exceedingly convenient for cleaning small quantities of gold-bearing sand collected in the dif- ferent arrangements made use of in placer mining. Amalgam can be - Separated from sand by washing, almost as readily as gold, and the pan is therefore frequently used for this purpose. Panning is appa- rently a very simple process ; but in order to use a pan so as to wash quickly, and at the same time without loss of gold, considerable practice is required. The Cradle.—This apparatus somewhat resembles in size and shape a child’s ordinary wooden cradle, and stands on similar rockers. The box is usually about forty inches in length and twenty in width, with one end from fifteen inches to two feet in height, the sides being sloped off at the lower extremity like those of a coal-scuttle. The construction of a cradle and the method of using it will be understood by reference to Figs. 8 and 9. At the upper end of the cradle is the hopper, or riddle box, 4, 134 : GOLD, twenty inches square and six inches in depth, of which the bottom is composed of sheet iron, thickly perforated with: holes half an inch in diameter. This is not fastened to the cradle, but can be lifted on and off at pleasure, and fits into it so as to be quite steady when in its right position. Beneath the riddle is placed an apron, 0, made by stretching a piece of canvas on a framework resting on fillets, inclined Eye. 8: SECTION OF CRADLE. WASHING WITH CRADLE. from the bottom edge of the riddle towards the head of the cradle, whilst across the bottom are nailed two riffle bars, c, about three- quarters of an inch in height, one towards the middle, and the other at the lower end. In order to work with this apparatus, which stands on rockers, d GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 135 the dirt is shovelled into the hopper; the cradler sits or kneels by the side of his machine, and whilst, with a ladle or dipper m one hand, he pours water upon the dirt, he with the other gives a rocking motion to the cradle. By the action of the water and motion together, the dirt is rapidly disintegrated, and passing through the riddle falls upon the apron, by which it is carried to the head of the cradle box, and from thence flows along the bottom, and finally escapes at the lower end, leaving the gold, black sand, and heavier particles of gravel, behind the riffle bars nailed across it. The pay dirt usually contains a great many large stones, which remain on the hopper, from whence those which are so large as to give an’ unplea- sant jerk to the cradle in rocking are removed by hand. The smaller ones, however, are allowed to remain until a hopperful of clean stones has accumulated, when the cradler, rising from his seat, first looks them over to see that there is no gold among them, and then takes out the riddle box, and with a jerk throws out its contents. The rocking motion of the cradle not only assists the disintegration of the dirt, but also tends to keep the sandy deposit behind the riffle bars from becoming too solidly packed, which, by preventing the particles of gold from settling at the bottom, would cause a con- siderable loss. é The operation of washing with the cradle is merely a repetition of the processes above described; but, in order to prevent loss of gold, it is necessary to clean up the cradle box from two to three times a day, according to the richness and nature of the wash dirt which is being worked. To do this, the hopper is first lifted off, and the apron re- moved, in order to get readily at the bottom of the cradle, which is then carefully scraped with an iron spoon, and the dirt collected in a pan for the purpose of being subsequently panned out. The larger proportion of the gold naturally collects above the riffle bars ; and when it is in a very finely divided state, it is sometimes found advan- tageous to place the hopper over the lower. end of the cradle, which will thus take double the length of apron, and oblige the stuff washed to pass over a longer surface before leaving the machine. If, in this ease, the apron be made of a thick woollen cloth, a considerable amount of fine gold will be retained on its surface, and on cleaning up the machine, it can be readily washed off into a pan. For the con- venient supply of a cradle, water should be conducted, by means of a small ditch or gutter, to a pit sunk near its head, serving as a reser- voir, and from which it is dipped out by means of a basin-shaped 136 GOLD. ladle, provided with a short wooden handle, and capable of containing from three to four quarts. The difference of level between the upper and lower ends of the machine should, under ordinary circumstances, be about two and a half inches, but this may be slightly varied in accordance with the fineness of the gold, and the nature of the dirt to be washed. The amount of dirt that can be washed by one man in a day, will evi- dently depend on the quantity of clayey matter it contains, and varies from one to three cubic yards. The dirt is shovelled into a pan or bucket, and from thence thrown into the hopper, the miner estimating the amount of work done by the number of pans or buckets washed. Although the cradle is frequently worked by one man, washing by this machine can be more expeditiously and cheaply conducted by two persons, since, m order to keep it in constant operation, there is always sufficient work for a cradler and a shoveller. In that case, one of the miners attends the cradle, whilst the other, who is provided with a couple of buckets or pans, fills them alternately with dirt, always keeping a full one near the cradle, so that he can at once pick it up and empty it into the riddle box. When a cradle is worked only by one man, he has continually to stop working in order to discharge the - stones from the riddle, and fetch more dirt, and during this time the sand and clay retained by the riffle bars are liable to pack, and have to be loosened with a spoon, or scraped, before again beginning to wash. It has been found in practice that the weight of water re- quired for working a cradle is at least three times that of the dirt washed, and consequently, where there is no means of conducting a supply to the cradle, it is taken to water, and the wash dirt transported to it. It is of great advantage to the miner when he can place his cradle within a few feet of the pit from which he obtains his pay dirt, and it is also essential that he should have an adequate supply of water and a sufficient fall to enable him to get easily rid of his tailings. , The rocker is neither an expeditious nor economical method of washing, as it not only loses fine gold, but also gets. through but one- fifth the amount of work that the same number of hands can perform with a tom, and less than one-tenth of that which an ordinary sluice will accomplish, but is nevertheless peculiarly adapted to certain descriptions of diggings. In all gold-producing countries there are numerous little gullies and ravines containing coarse gold, but in which no water can be obtained for washing, except immediately after heavy rains, and GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 137 then only for a few days at a time; and in such situations the cradle can often be used with advantage. It is in the first place cheap, does not require a large quantity of water, and being exceedingly portable, cap, when the supply fails, be readily removed to the bank of some pool, where a supply of pay dirt can be obtained. The great defect of the cradle is the tendency of the sand to pack behind the riffle bars, which causes the bottom of the box to assume a plain even surface, over which gold is liable to pass off and be- come lost. It is consequently necessary, after the machine has been allowed to stand, if only for a few minutes, without rocking, to stir up the sand in the bottom before reeommencing the operation. Mer- cury is sometimes employed in the rocker, but this is not general, and its use in this apparatus is not generally to be recommended. In the early days of Californian and Australian gold mining the rocker was very commonly employed ; but now that the supply of rich shallow pay dirt has become nearly exhausted, it is but little used by European and American miners, although still a general favourite with Chinese diggers. The Tom.—The tom or long tom was almost universally employed in the Californian placers up to the year 1852, but is now rarely met with. It consists of a roughly-made wooden trough, or spout, about twelve feet in length, twenty inches in width at its upper end, and gradually widening to thirty inches at the other extremity, with its bottom covered by a plate of iron to prevent-wearing. The sides, from eight to ten inches in depth, are cut off obliquely from the bottom upwards, so that the wide end may be closed by an inclined riddle of punched sheet iron, precisely similar to that forming the bottom of the hopper of an ordinary rocker. This trough is sup- ported on trestles or logs, so as to have an inclination from the head downwards of about twelve inches, and beneath the strainer of sheet iron is placed the riffle box, which may be used either with or with- out quicksilver, and from which the rich dirt is, from time to time, cleaned out and panned up, as in the case of the rocker. _The general arrangement of the tom and its riffle box will be un- derstood by the aid of Figs. 10 and 11, which show the method of fixing this apparatus. A stream of water is brought by the spout, A, on to the tom, B, and the dirt is thrown in near its head by one man, whilst another keeps it constantly stirred, either by a shovel, or by a fork provided with humerous prongs, with which he from time to time removes the large 138 . GOLD. stones, and throws back against the current such pieces of clay as continue to hang firmly together. The number of men working at a time varies from two to four, according to the tenacity of the dirt, and the quantity of water available. The small stones which gradually - accumulate in the angle between the bottom and the perforated iron plate, b, are removed when necessary, and a fresh supply of pay dirt is continuously shovelled in at the head of the trough. Fia. 10. Pies 11. PLAN oF Tom AND RiFFLE Box. This arrangement is most applicable to diggings yielding but a limited amount of pay dirt containing coarse gold; but even when quicksilver is used behind the riffles c, in the riffle box c, the loss of fine gold is considerable, although the constant falling of the water on it generally prevents packing. — The sluice, which has now generally superseded the tom, is not only capable of washing a much greater quantity of dirt in a given time, but is also attended with a less loss of gold. Puddling Box.—The puddling box is a rough wooden case, usually about six feet square, and eighteen inches in depth, which is used for disintegrating very tough clay. The dirt is thrown into this box, and a considerable quantity of water added, with which it is stirred up by a rake, having very long and strong teeth, until the whole of the GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 139 clay is held in suspension, when a plug, a few inches from the bottom, is removed, and the slimy matters run off. More clay and water are now introduced, and the operation is repeated until the box becomes filled with gravel and coarse sand to the level of the plug hole, when it is removed for the purpose of being washed up by the pan, cradle, or some similar appliance. In California, the pud- dling tub is only employed in diggings carried on on a very limited scale, and never where the sluice or the hydraulic process can be introduced. In Australia, on the contrary, where the supply of water is often scanty, washing by the aid of a puddling machine is generally resorted to. For small operations, half a porter barrel is sometimes used, the clay being stirred with a shovel; but in works conducted on a more extensive scale, an arrangement not unlike a brickmaker’s pug- tub, set in motion either by horse or steam power, is generally used. This machine, when worked by steam power, consists of a large shallow tub with an upright shaft standing in its centre, provided with strong rake-like arms, set in motion by a mitre wheel attached to the perpendicular shaft. From these tubs the thin mud is tapped off, in the same way as from the puddling box, and the residues after- wards subjected to some process of washing. These machines are so general in Australia that in 1860 no less than 3,958 of them, worked by horse power, were in use in Victoria alone. The Sluice.—This arrangement is now almost universally ernployed by Californian miners, and by it are, probably, collected at least eight- tenths of the gold furnished by the placer mines of that country. The sluice is generally a long wooden trough, having a considerable inclination or declivity, into which the pay dirt is shovelled, and through which a rapid stream of water is continually flowing. The bottom of this trough is provided with a series of riffles, generally containing mercury, by which the gold is retained, whilst the clay, sand, and gravel are carried off by the force of the current. The ordinary sluice is composed of a series of rough wooden boxes, each twelve feet in length, generally varying from sixteen to twenty inches in width, and from ten inchey to a foot in depth, made of inch-and-half pine planks. In order to facilitate the making of these sluice boxes, the boards for the bottom are sawn, at the mill, four inches wider ‘at one end than at the other. This enables the narrow end of one box to be fitted into the wide end of another, and in this way a sluice, several hun- dred feet in length, can be rapidly put together, or, if necessary, taken apart and removed. The descent of a sluice is called its grade, and is 140 GOLD. commonly from ten to eighteen inches on each box of twelve feet in length, and, consequently, a sluice having the latter inclination would be said to have an eighteen-inch grade. The grade to be employed is regulated by the position and length of the apparatus, and the nature of the dirt to be washed. The greater the descent, the more rapid will be the current, and, as a consequence, the greater is the danger of fine particles of gold being carried off by the water and lost. If the angle at which the boxes are set be considerable, the dirt will be rapidly disintegrated, but the danger of losing fine particles will be increased ; whilst if the stuff to be washed contains much clay, a small inclination will not easily effect its disintegration. Generally speak- ing, therefore, a sluice with a rapid current of water requires to be made longer than one set more nearly on a level, and, for this reason, where a long sluice cannot be employed the inclination must be diminished. Economy and the convenience of working render it necessary that the sluice should not be raised too high above the surface of the ground, and therefore the angle at which it is laid is somewhat influenced by the conformation of the country. There are, obviously, various considerations to be attended to in finding the proper grade ; but in most instances a fall of less than ten inches, or more than twenty inches, on the length of a twelve-foot box, ‘is not regarded as suitable for the ordinary sluice. In many claims the pay dirt contains large blocks of stone and boulders, each weighing from fifty to several hundred pounds, which have to be passed through the sluice, either whole or after being broken, and in such cases a large body of water and a rapid current are essential. The upper part of a sluice is sometimes made steep in order to effect the disintegration of the dirt, whilst the lower is placed at a less inclination for the pur- pose of collecting the gold, and this arrangement is often found advantageous. The ordinary clay met with in pay dirt is entirely taken up in suspension by the water of a sluice with a moderate grade, within the first two hundred feet, and the remainder of the boxes beyond that point are only useful in collecting gold. It is scarcely necessary to observe that when the gold is coarse, the inclination may be safely made greater than when it occurs in a finer state of division. In some claims the clay is so extremely tenacious that it will roll into balls, which are carried the whole length of an ordinary sluice without being much diminished in size. This has to be carefully avoided, by breaking up the lumps at the head of the GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 141 sluice, since balls of plastic clay passing through the boxes not only do not give up the particles of gold they may contain, but are also liable to pick up others over which they may pass in their course. Sluice boxes are always provided with some sort of false bottom for the purpose of retaining the gold, which would otherwise not only be taken away by the force of the current, but the bottoms them- selves be rapidly worn out by the attrition of the stones and gravel passing over them. In the majority of cases the false bottoms employed are composed of longitudinal bars a, from two to four inches in thickness, from three to seven inches in width, and about five feet six inches in length. These are wedged in the boxes, from an inch to two inches apart, by the cross pieces 6, so that two lengths of bars are fitted in the bottom of each box, as seen in Figs, 12 and 13, PLAN oF SiuIcE Box. Hie. 1s — oo —— FILLE LiL SN ZIZIIZL WZLLLE WIZI ILI LL EE LIL ILE ZZ - SECTION OF SniuIcE Box. The whole of the boxes are thus fitted with these bars, and the bottom of the sluice consequently represents a series of rectangular depressions, of the thickness of the bars, and several feet in length, in which the gold, mercury, and amalgam are caught. It is evident that the larger pieces of gold will be readily caught by such an arrange- ment without the use of quicksilver; but in order to retain the finer particles, the employment of this substance becomes essential. 142 GOLD. When the sluice boxes have been all joined together, and the - bars wedged into the bottom of each, the apparatus is ready for working ; for although the boxes are generally made of planks rough from the saw, the swelling of the wood, on the introduction of water, and the clay which gets into the joints, as soon as the wash dirt is thrown in, quickly closes them, and renders the whole arrangement _ water-tight. The pay dirt is now shovelled in at the head, the number of men employed being regulated by the size of the sluice,'. and the nature of the dirt, which the eurrent rapidly disintegrates, carrying off the clay in suspension, and rolling the pebbles and boulders onward by the force of the stream. The first dirt thrown in closes the joints of the troughs, and fills the spaces between the riffles, but nevertheless leaves a sufficient number of pits and inequalities for retaining the particles of gold and amalgam. The amount of dirt which can be thrown into an ordinary sluice in a day by one man, depends on the compactness and state of agere- gation of the deposit, and varies from about two to five cubic yards. About one hour and a half or two hours after the commencement of sluicing, some mercury is poured into the head of the apparatus, from whence it gradually finds its way downwards, in the direction of the current, but is still chiefly retained by the upper boxes of the series. Smaller quantities of quicksilver are also introduced between the bars, along in various places in the boxes; and the greater the amount of fine gold present, the larger must be the quantity of mercury used. When the gold contained in the dirt is exceedingly fine, an amal- gamated copper plate is sometimes resorted to. This plate is generally three feet in width, and six in length ; is set nearly level, and, when the sluice is avery large one, the stream is frequently divided into two or three separate portions, each of which is conducted over a distinct amalgamated plate.* A well-amalgamated copper plate is considered as effective for saving fine gold, as an equal surface of pure mercury, and is not only cheaper, but also more easily managed. The copper plate is,in most instances, placed at a considerable dis- tance from the head of the sluice, and the dirt and water falling upon it first passes through a sheet iron screen, having apertures half an inch in length, and a sixteenth of an inch in width. The amalgama- tion of the copper plate is effected by first washing over its upper face with dilute nitric acid, and then rubbing on, with a rag, quicksilver * For the purposes of hydraulic mining sluices from four to seven feet in width are frequently employed. GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 143 on which a little diluted nitric acid has been first poured, so as to form a certain amount of nitrate of mercury. When a plate has been thus well covered, this operation need never be repeated, it being only necessary to sprinkle its surface occasionally with a little fresh quicksilver, in proportion as the gold caught converts it into a solid amalgam. ‘In order that these plates should act satisfactorily, it is essential that the current should be slow, and the water shallow, since other- wise a considerable portion of the fine gold might escape without coming in contact with the face of the plate; and it is for this reason that in large sluices it is usual to divide the stream, and to pass each portion over a separate surface of amalgamated copper. Wherever a particle of gold has attached itself to the face of an amalgamated plate, others will be found to arrange themselves around it, evidently becoming more readily attached to those portions of the surface on which gold has been already caught, than on those on which no deposit of this metal has previously taken place. When a newly amalgamated plate is first used, its surface is apt to become tarnished by the formation of subsalts of copper, which forming a green slime, interfere with the adhesion of gold. This should be carefully scraped off, and the place from whence it has been removed rubbed with a little fresh mercury. The larger the amount of gold deposited on the surface of a copper plate, the better it is considered for the purpose of arresting the progress of fine particles of that metal ; but as the accumulation of a very large quantity of auriferous amalgam might give rise to losses through theft,-it is injudicious to allow too ereat a thickness to accumulate before being removed. For this purpose, the plate is taken up and heated over a fire, until the hand cannot bear to remain on it beyond about a second, when the amalgam be- comes softened and loosened, and can be easily removed by scraping. The plate, after cooling, may. now be again rubbed with quicksilver, without the aid of nitric acid, and is again ready for use. A copper plate, to be employed for this purpose, should not be too thin, since it would quickly become permeated by the quicksilver, and break almost as readily as glass ; a plate of one-sixteenth of an inch in thickness will, however, with careful management, last, several years. It is evi- dent that the coarser gold will be caught near the head of the sluice, and the finer particles be arrested further down, in proportion to their state of division. When dirt contains a large proportion of coarse gold, the mercury is frequently introduced, at a distance of from forty 1aa wae GOLD. to sixty yards from the head, so as to catch only the fine gold in the form of amalgam. The collection of the dirt which accumulates in the bottom of the sluice, and the separation from it of the gold, amalgam, and quick- silver, is called the cleaning up, and the time between one cleaning up and another is called a run. In most cases, an ordinary sluice runs only during the day, but, in some instances, the work is continued throughout the whole twenty-four hours. A run commonly lasts about a week, and the cleaning up is not unfrequently reserved for the Sunday. This usually occupies about half a day, and consequently, on account of the loss of time entailed, must not be too frequently repeated. In some claims it is not done until the riffles are so worn and damaged, as to require to be overhauled and repaired. When a-cleaning up has been decided on, no more dirt is thrown into the sluice, and the water is allowed to run through it until it passes off quite clear at the lower end. Some six or eight sets of bars are now taken up trom the head of the sluice, and the dirt is washed down ; whilst the gold and amalgam, which had been caught between them, is arrested by the first remaining set of bars, from whence it is taken out with a scoop into a pan or bucket. Another six or eight sets of riffle bars are now taken up, and the operation . repeated, until the whole length of the sluice has been cleaned up. The amalgam and mercury taken from the sluice are first sepa- rated from any admixture of sand by panning, and then strained, either through buckskin, or a piece of close canvas, which allows the liquid quicksilver to pass through, but retains the more solid amalgam. In order to obtain the gold in a metallic state, the amalgam must be subjected to a degree of heat capable of volatilising the quicksilver, which is thus expelled, leaving the gold in the form of a porous mass, of a light yellow colour. This operation is most economically performed in a cast iron retort, provided with a refrigerator, by which the mercury is condensed, and can be collected for subsequent use; but in many cases, and particularly in small claims, the miners drive-off the quick- silver by heating the amalgam on a shovel, or on an iron plate, by which method of proceeding it is of course volatilised and lost, besides exposing those around to the danger of injury from the metallic vapours evolved. The amalgam obtained, after squeezing the super- fluous mercury through cloth or buckskin, is generally calculated to afford from thirty-five to forty per cent. of retorted gold. As before stated, the riffle bars are often between five and six feet GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 145 in length, and sawn in the direction of the grain of the wood; but these, in claims where large quantities of pebbles and boulders are enclosed in the dirt, are rapidly worn away, and in some cases the bars are cut across the grain of the timber, and placed end upwards in the sluice. Riffles so constructed are found to last three times as long as those cut in the ordinary way, but it is generally difficult to get them more than about three feet in length, and consequently they require a little more time for fixing than the usual longitudinal bars. These block rifles, instead of being placed longitudinally in the boxes, are sometimes fixed transversely across them, and at distances of about two inches apart. In small sluices, the bars are not always placed either longitu- dinally or transversely, but sometimes in a series of ZIG@ZAgS, aS seen in Fig. 14, ZIGZAG RIFFLES. The first bar in the sluice is nailed at an angle of 45° with the course of the box itself, but does not touch the opposite side, be- tween which and its extremity is left a space a, of about an inch in width. Immediately below this open space another bar is fixed, at right angles to the first, touching the side of the box beneath the opening, and stopping an inch short of the other side. This is con- tinued until near the lower end of the sluice, where there are either longitudinal riffles, or transverse blocks, as before described. When this arrangement of the bars is employed, it is evident that, although a large proportion of the dirt and water will pass over them directly down the trough, the heavier particles will sink to the bottom of the boxes, and being directed by the oblique riffles, will assume a tortuous course through that portion of the sluice. At a short distance from the head of sluices of this description is placed a vessel containing mercury, in which is a small hole, fron. whence it is allowed, very slowly, to escape into the sluice. This quicksilver runs down the | i dees he GOLD. arrangement, following the course of the riffles ; and overtaking, and coming in contact with, the particles of gold, unites with it, and forms an amalgam, which is retained in that portion of the sluice provided with ordinary longitudinal riffles. It is necessary that these, and all other descriptions of sluice, should be carefully watched, in order to prevent any jamming of the larger boulders, or any local accumulations of dirt, which would interfere with their efficient action, and result in loss of gold. In small sluices, it is sometimes customary not to allow the large pebbles to run throughout their whole extent, and stones of more than a few pounds in weight are therefore thrown out by a man provided with a prong, having numerous blunt parallel teeth, which, without being liable to injure the wood of which the boxes are made, enables him to remove the stones. Another contrivance for collecting fine gold is to impregnate the wood of which the riffles are made, with mercury. This is done by means of an ordinary gas-pipe, which is first ground to a thin edge at one end, and then driven into the wood forming the block riffles. On subsequently filling this pipe with quicksilver, the pressure of the column forces it into the pores of the wood, which afterwards acts somewhat similarly to the amalgamated copper plates before described, except that the resulting amalgam is removed by simply scraping the surface of the blocks. This process is not, however, often adopted, and is not generally to be recommended, since it requires more time to prepare the blocks than to amalgamate an ordinary copper plate, besides which its action is, on the whole, not so satisfactory. When two companies are working claims side by side, a double sluice is, for the sake of economy, sometimes employed. In this case the boxes are made of double the usual width, and are divided in the middle by a longitudinal partition, so as to form two distinct sluices. This arrangement is also employed in claims where, to prevent loss of time, one side of the trough is made use of, whilst the other is being cleaned up; or in localities in which the supply of water is, during a portion of the year, sufficient for w orking both sluices, whilst in thé dry season the quantity at command is only enough foes one. The wnder-current sluice, another modification which is often found advantageous, is represented Fig. 15. In this arrangement a grating is placed in the bottom of the lower extremity of the last box in the series, and beneath this is introduced another sluice with a lower gerade and fresh supply of water. The GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 147 impetus acquired by the large boulders, in the first sluice, causes them to roll off over the grating, and, together with a portion of the water, to escape at the lower end; whilst the introduction of clear water, the less inclination, and more moderate current, determine the arrest of inany particles of gold that would, under ordinary circumstances,’ be carried off and lost. t iii. tT LC ae a | | if zy ~~ UnpEr-Current Suvuicr. The rapid wearing of all kinds of wooden rifiles, and the facilities they afford for stealing the auriferous amalgam by night, has led to the introduction of what are known as roc: s/ wices, but these are atteuded with the disadvantage of being more difficult to clean up, and consequently to prepare for working after being cleaned up, than any of those before described. The sluice itself is formed of the ordinary rough wooden boxes, which are coarsely paved with lenticular rolled pebbles, laid on edge, and which, when the wash dirt has passed over them for a short time, become securely embedded by the sand which collects between them. In tail sluices the paving stones employed are generally larger than those used for the bottom of an ordinary sluice. These stone bottoms are only employed in wide boxes, and have gene- rally an inclination of about an inch to the foot. When the sluice is cleaned up, the stones have necessarily to be removed, and the bottom of the boxes repaired before again commencing to wash ; but this, with L 2 4 hod 148 GOLD. experienced hands, is performed with considerable rapidity, since a miner, accustomed to the business, will pave some 200 feet of an ordinary sluice in the course of a day. Tail sluices are arrangements for collecting gold still retained by the dirt which has passed through the ordinary sluice, and escaped being thoroughly impoverished in its progress. They are usually placed in a ravine through which the tailings from one or more sluices of the ordinary construction flow, and are only cleaned up after the Tait Suuices, Yusa RIver. (From a Photograph.) expiration of several weeks, receiving, in the meantime, no further attention than is necessary to prevent their choking. Tail sluices are generally large, long, and paved with blocks of stone, or wood placed on end, and often afford large profits to their proprietors. Both the dirt and water with which they are supplied is furnished by the sluices emptying into them, and they are in some instances made double, so that one side may be in working order whilst the other is being cleaned up. Many of the tail sluices on the Yuba are GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 149 of extraordinary length, and some of them have been constructed as much as twenty feet in width. Fig. 16 is a view of two of the tail sluices on this river. All the varieties of the sluice which have been hitherto described require wooden boxes or troughs, through which the water is con- ducted ; but in localities where there is a large supply of water, plenty of pay dirt of low produce, and the necessary declivity, a sluice is sometimes improvised without the use of wood. Such arrangements are called ground sluices, and in order to prepare one, a small cutter is first made with a sufficient inclination through the dirt to be washed, and into this is directed a stream of water, by the action of which the channel rapidly becomes deepened and enlarged. As soon as the sides and bottom of this ditch have ceased to become rapidly eroded by the action of the current alone, the miners begin to assist the operation by pinching off scales of ground from the bank, which, falling into the stream, are acted on precisely as in the case of the ordinary board sluice. No mercury or riffles are employed in the ground sluice, but unless the bottom consists of a rough and irregular bed rock, a few large stones should be roughly thrown in for the pur- pose of arresting the gold, which, if the surface were not more or less uneven, would be liable to pass off and be lost. When a considerable amount of dirt has been passed through a sluice of this description, the water is diverted, and the auriferous matters, thus partially washed, collected, and cleaned up in a tom, cradle, or short box sluice. The ground sluice is seldom employed on claims where mining is continuously carried on, and is most advantageously introduced in localities in which water is abundant for a few days only, after heavy rains, and consequently where it would not be judicious to erect large and expensive sluices. When, as is sometimes the case, either in hydraulic or other mines, a sluice passes through an adit level, or day tunnel, it is called a tunnel sluice, but these differ in no respect from other sluices except in their situation. River Mining—River mining consists in turning the stream of a river, by means of a dam in connexion with a ditch or large wooden flume, and subsequently washing the dirt, found in its bed, for the gold which it may contain. The streams selected for this purpose are generally mere mountain torrents, of which the banks are steep and irregular ; and consequently a ditch being impracticable, recourse is had to a rough wooden trough or flume. River mining can only be successfully carried on during the summer and early fall, when the © hou) 7 GOLD. water is not only low, but the miner will not be subject to have all his work destroyed by a sudden freshet, which might sweep before it his flume, dam, and all his tools together. This branch of mining is, however, subject to many disadvantages, from which the other deserip- tions are comparatively free. In the first place it cannot be carried on during more than half the year, and as the miner has no means of prospecting under the surface of the water, and thereby ascertaining the value of the dirt, it may, after he has expended a large amount of time and labour, prove almost worthless when the diversion of the stream has been effected. Secondly, he is constantly exposed to the danger of floods, which may, by carrying away his flume and destroy- ing all his work, suddenly deprive him of the advantages to be derived from his outlay of capital and labour. These disadvantages, coupled with the fact that the principal river washings have been already exhausted, have almost done away with this description of mining in California. In some: few instances enter- prises of this kind have been attended with highly remunerative results ; but in the majority of cases, the gold extracted has not repaid the labour and capital expended to procure it. A long flume of a sufficient capacity to carry off the whole of the water of a consider- able river, is in itself an expensive piece of work ; but when it is taken into consideration that a greater or less amount of leakage from the dam has always to be contended with, and that water is constantly finding its way into the river bed from the various ravines trending in that direction, it becomes evident that the difficulties of river mining are of no ordinary character. It is therefore necessary to provide machinery for pumping out this influx of water; and as large rocks, often weighing several tons, are frequently met with, they have to be removed, by means of cranes, before the most valuable dirt can be reached. River mining is consequently never attempted by single individuals, but is always carried on by associated companies, either entirely composed of working miners, or by miners assisted by the storekeepers and other substantial inhabitants of the neighbourhood. In the latter case, those who are not directly connected with the business pay their proportion of the expenses in money, the merchants supply the necessary provisions, the saw-mill proprietors the wood, and the carpenters make the flumes, whilst the miners prepare the dam, and perform any other work that may be required. Beach Mining—Beach mining is. the process of extracting gold from the sands on the sea-shore, and has been extensively carried on GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 151 between Cape Mendocino in California, and the mouth of the river Umpqua in Oregon. The beach is here narrow, and hes atthe foot of a bluff of auriferous sand, which, in stormy weather, is undermined by the waves, and the lighter constituents being washed away, leave sands which are often rich in gold. The gold is here found in a finely divided state, associated with the heavier and darker coloured sands, the position of which is frequently changed by the action of the tides and currents. In this way, a part of the beach which may, on one day, be deeply covered with sand, in which particles of fine gold can be readily seen, will, on the following, be left either bare, or covered with sand containing little or no gold, and it therefore requires con- stant attention on the part of those directing the operations, in order to select the most auriferous descriptions for treatment. The Companies engaged in this kind of mining usually consist of about ten men, including the foreman, who every morning rides along the beach for a distance of about two miles, on either side of the camp, for the purpose of ascertaining where, on that day, the richest sands are to be met with. When this has been determined, each man of the company proceeds to the spot with two pack mules provided with raw hide sacks, a/forjas, in which the sand is collected and carried to the washing place, which is sometimes several miles distant. Sea water is occasionally employed for this purpose, but fresh is generally preferred; and for this reason, the sand is in most cases transported to a running stream at no great distance from the shore. It sometimes happens that rich sand is not met with within twelve miles of the camp, but in such cases it requires to be highly auriferous in order to support the expenses of transport. The richest sands are found far down the beach at low tides, and consequently when such a tide occurs during still weather, every exertion is made to obtain as large a supply as possible ; since with high tides and a rough sea, there is little to be done in this class of mining. The sands thus obtained, being entirely free from clay, are very readily treated, and a couple of days’ working with a sluice will generally effect the washing of all the sands collected during a month. Water Supply.—In proportion as the shallow placers in the ravines and river beds of California, from which the first supply of gold was obtained by simple means and at a small cost, became more or less completely exhausted, the necessity of devising some ready method by which the deep placers could be economically worked, naturally forced itself on the attention of the mining community, In order to accom- 152 GOLD. plish this object, it was necessary to convey a copious supply of water to auriferous deposits far above the level of the rivers in the vicinity, and often situated at a great distance from the present streams of the country. This required the expenditure of large sums of money for the construction of the canals and aqueducts, by which it was brought from springs and reservoirs, at elevations such as to command the largest and most important diggings. This demand for the association of labour and capital soon called into existence numerous canal and ditch companies, the shareholders being for the most part miners, whose limited resources generally obliged them to borrow money from the local bankers, at rates of interest varying from three to five per cent. per month. In this way the Middle Yuba Canal Company was organised in 1853, the water being brought from a point on the Middle Yuba a little below Woolsey’s Flat, where the river was dammed and the aqueduct commenced. The total expenditure involved in this enterprise, including the various branches, ditches, reservoirs, and extensions, has amounted to $600,000 or about 120,000/.; and the works are now capable of supplying thirty-eight cubic feet of water per second, which could at a comparatively small expense be increased to sixty cubic feet. The first-named quantity is considered equivalent to nearly 1,500 inches, miner’s measurement, and the second to 2,280 miner’s inches.* The Eureka Canal was commenced in 1856, and has cost, including the various reservoirs and branches, $1,000,000, or 200,0002. The Eureka Lake is the largest reservoir now in connexion with this aqueduct, although it has been proposed to connect it with the Truckee Lake, which is a still more considerable body of water. At the outlet of the Eureka Lake a substantial granite dam raises its waters to the height of forty-two feet above their natural level. This is retained by a natural abutment of granite, capable of receiving, if necessary, an additional height of twenty feet. The width of this structure, at the base, is 120 feet, its height is seventy feet, and its length from bank to bank 250 feet. Its water face has a double lining of securely-fastened two and a half inch planking, and the flow of water is regulated by a sluice placed in a tunnel of strongly-arched masonry. The capacity of this reservoir is estimated at 933,000,000 cubic feet, or about five months’ full supply of the canal. During from four to five months in * The miner’s inch of water, in California, is the quantity which will flow through an opening one inch square under a mean head of six inches, and the working day is generally calculated at ten hours. oe GOLD WASHING IN CALIFORNIA AND AUSTRALIA. Loe each year, however, it obtains. the necessary amount of water from other sources. The snow accumulates in the Sierras, in great quantities during the winter months, and the melting of this not only supplies the flow of the streams, but also fills, to overflowing, the various mountain lakes and artificial reservoirs, in which the waters are stored in reserve against the droughts of Jatesummer and autumn. Besides this main reservoir, there are several others, of which Lake Faucherie is the most important. The Eureka Canal is constructed partially of earth and partially of a wooden fluming: the dimensions of the main flume are five feet nine inches in width, and three feet in depth, with a fall of sixteen feet per mile* The discharge is ninety-six and a half cubic feet of water per second, or 3,667 miner’s inches. We shall therefore be below the truth if we assume that this canal is capable of supplying, after allowing for leakage, 3,000 inches of water in a working day of ten hours, which is equal to 7,200 inches during the twenty-four hours, or, as the discharge per second is ninety-six and a half cubic feet, it will afford 8,337,600 cubic feet of water in twenty-four hours. Among the most remarkable objects that strike the traveller on first visiting the mining regions of California, are the lofty aqueducts, con- structed of trestle-work, for the purpose of conveying water across deep valleys and ravines. The Magenta and National aqueducts are the most considerable constructions of this description on the line of the Eureka Canal. The Magenta aqueduct is 1,400 feet in length, whilst the length of the National is 1,800 feet. The greatest height of the former is 126 feet, and that of the latter 65 feet. The dimen- sions of the flume are seven feet in width by fifteen inches in depth, and its inclination one foot in a hundred. In order, as much as possible, to avoid the action of the wind, which often blows strongly up the valley, the sides are made low, and considerable width given to the bottom. The legs of the trestles were all cut out of trees which grew in the vicinity, and are without a splice from foundation to top. The sides of the flume are made of whole scantlings, seven and a half inches in width, and thirty feet in length. The trestles are placed thirty feet from centre to centre, and are well and securely braced. This aqueduct was put together in sections of thirty feet, and each, when completed, raised into its place from the spot on which it was constructed, by which means the use of scaffolding * . . . 5 « z % . . When a less inclination is given, the water is liable to freeze in winter. 154 GOLD, was rendered unnecessary. The agereeate length of all the ditches belonging to the Eureka Company is about 200 miles. The foregoing description of the works of the Eureka Lake Water Company will afford some idea of the extensive scale on which such enterprises are conducted in California, as nearly all the more im- portant mining districts now receive a plentiful supply of water by similar means. The following woodcut, Fig. 17, will serve to illustrate WARS AN 4 SS WT / Wy oY BOE an < =) \Vh FLUME NEAR SMARTSVILLE, YUBA CouNTY. (From a Photograph.) the method adopted for the construction of high aqueducts for mining purposes. | Hydraulic Mining.—In order to treat most successfully the exten- GOLD WASHING IN CALIFORNIA AND AUSTRALIA. L55 sive beds of detritus forming the deep placers previously described, the following conditions are involved :— 1st. Whatever may be the depth of the auriferous gravel, the whole must be removed down to the bed rock. 2nd. This must, as far as possible, be effected by the force of a column of water, since manual labour becomes too expensive when from 1,500 to 4,500 cubic yards of dirt have to be disposed of during each working day of ten hours. 3rd. The mechanical disintegration of the more or less indurated eravel must go on contemporaneously with the washing of the result- ing debris, and be effected by the same supply of water. 4th. Provision must be made for readily disposing of the large amounts of refuse resulting from the removal of such vast masses of auriferous gravel, In practice these conditions are fulfilled in the following way :— After having selected a sufficient extent of suitable ground, the water from a canal is brought, by side flumes or aqueducts, to the head of the mining ground, with an elevation of from 120 to 160 feet above the level of the bed rock, where it is conducted into a wooden tank, into which it constantly flows. This box is provided with a valve, and from it the water is conveyed to the bottom of the claim by means of a strong sheet iron rivetted pipe, from eight to fourteen inches in diameter, communicating at the bottom with a thick rectangular cast iron chamber, in the sides of which are apertures provided with slide valves and union joints, to which can be fitted strong flexible hose terminating in bronze nozzles from two and a half to three inches in diameter. The arrangement of the bulk head or pressure box, into which the water is conducted at the head of the column, will be understood by reference to Fig. 18. The flexible hose are usually made of closely-sewn heavy duck, and will, without any external support, bear the pressure of a column of about fifty feet in perpendicular height ; when however, as is most frequently the case, the pressure employed is greater than this, they require to be strengthened by iron rings. The bands employed are placed over the hose at intervals of three inches from each other, and connected by means of four longitudinal cords, dividing the circum- ference into equal divisions. These crinoline hose are very flexible, and will, if well made, support, without danger of bursting, the pressure of a column of water a hundred and eighty feet in height. Instead of increasing the strength of the canvas hose by the use of 156 GOLD, iron rings, they are sometimes tightly covered with a netting of cord, half an inch in diameter, forming meshes two inches square. In some claims also the cast-iron chamber at the bottom of the pressure pipe is dispensed with, and a separate iron pipe connected with each nozzle, or two or more hose joined to each by means of TF pieces; but the use of one large pressure pipe with the close chamber at the bottom is, in most cases, to be preferred. From each of these ISSN \ ON “Yj; My > Ulf iC \\ Se PressuRE Box, Yupsa Rrver. (From a Photograph.) nozzles streams of water are directed against the face of the gravel to be washed, with a force which can only be compared with that of ordnance, and the power developed by this means, where the supply of water is large and the height of the column considerable, is per- fectly astonishing. The volume of water employed varies in accordance with various local circumstances ; but it is not uncommon to see four or five such streams acting simultaneously against the face of the same bank—five hundred miner’s inches of water constantly dis- charged against the face of a bank, under a pressure of from sixty to a hundred pounds to the square inch, aided by its disintegrating and softening action, bring down large sections of the gravelly mass, GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 157 which fall with violence, and render it necessary for the workmen directing the operation to exercise great caution in order to avoid accidents, The number of men necessary to carry on the operations of a hydraulic claim is very limited, since, in addition to those engaged in directing the nozzles, only one person is generally employed in attending to the sluice, so as to prevent its being choked by the dirt washed down from above. The following woodcut, Fig. 19, shows the method of applying the jets of water against the side of a bank of dirt. Fra. 19. HyprauLtic Minineg, WASHING DOWN BANK. (From a Photograph.) The debris thus produced becomes rapidly disintegrated, and, borne along by the resistless force of the water, is carried forward to the sluice, through which it passes with the whole volume of the turbid stream. Banks of more than eighty feet in height are generally worked in two benches. The upper half is never so rich as the lower, but is 158 GOLD. usually less compact and more easily removed by the action of water. The lower section, on the contrary, is often very closely cemented together, and most frequently requires the aid of gunpowder in order to loosen it, so as to enable the water to remove it with sufficient rapidity. For this purpose a tunnel is driven into the bank, at the level of the bed rock, for a distance of some fifty or sixty feet, and from its extremity another drift is extended on either side, at right angles, in which a large quantity of gunpowder is placed. The charge usually varies from fifty to two hundred barrels, which after being securely built in, is fired by a slow match, and by its explosion loosens a large mass of the compact conglomerate, which is afterwards readily acted on by the force of the currents of water brought to bear against it. When the conformation of the country admits of it, a tunnel is sometimes brought in from the nearest and most convenient ravine, at a considerable depth in the bed rock, at a gradient of from one in twelve to one in twenty, and varying in leneth from a few hundred to several thousand feet. Such tunnels have not unfrequently occupied from three to four years in driving, and have cost very large sums of money. On the extremity of this long tunnel a shaft is sunk, through which the pay dirt is washed, and the level itself becomes-a channel in which the sluice boxes are fixed, for the double purpose of directing the stream and collecting the gold. In such cases it is usual to employ a double sluice, in order that one side may be cleaned up whilst the other is in active operation, by which means all loss of time in working the claim is avoided. When this method of proceed- ing is adopted, the debris produced by the united action of the jets of water directed against the bank is rapidly carried forward by the current to the mouth of the shaft, down which it is precipitated with ereat violence, and being often accompanied by boulders of a hundred or two pounds in weight, a powerful disintegrating action is the result of the fall. In some claims a system of tunnels is extended in the bed rock, very much as in a coal mine; and after dividing the ground into separate blocks by proper levels, they are washed away by the hydraulic process, after which the whole mass settles down and is easily disintegrated by the action of water. The sluices employed in connexion with hydraulic mining are made wider than those used for other purposes, and are sometimes provided with wooden riffles, kept apart by shps of wood; in others their GOLD WASHING IN CALIFORNIA AND AUSTRALIA. 159 bottoms are paved with stone, as previously described. When wooden riffles are employed, they are composed of blocks of wood cut trans- versely across the tree, and placed end upwards in the sluice box. In this case the cavities which occur between the different blocks form the spaces in which the gold is collected, and are found very efficient for this purpose. A good general idea of the appearance of the sluice belonging to an ae hydraulic claim is afforded by Fig. 20. s Bia 20: SLUICE AND TUNNEL, TIMBUCTOO. (From a Photograph.) Rude as this method of saving gold appears, experience has shown that a larger proportion of the metal is collected by it than by any other process, and that at the same time the cost of handling a cubie 160 GOLD. yard of dirt is infinitely less by the hydraulic, than by any other system of mining. In fact, it would be utterly impossible to treat such enormous masses of dirt, as are now daily operated on, by any other known means. | As an illustration of the amount of work which can be performed in a given time by hydraulic mining, we give the results obtained at the Eureka Claim, near San Juan, California, where the bed of pay dirt is about 135 feet in depth.* The upper portion of this deposit to the depth of seventy feet does not contain a large amount of gold, but is easily washed, whilst the lower portion, having a thickness of sixty-five feet, is much richer, but cemented together, and the work is therefore carried on under conditions’ of considerable difficulty. The pay dirt is reached by a bed-rock tunnel of a great length, which cost on an average $8 per foot, and of which the total expense was $28,000. The work is carried on by means of four jets d'eau, discharging together about 208 gallons per second, or 12,500 gallons per minute, under a pressure of 140 feet. The whole of the operations are conducted by four men, and after the expiration of ten working days, the washing down of fresh earth is suspended and the sluices cleaned up. During this period of ten days about 36,500 cubic yards of gravel are worked over, the cost of working being nearly as follows: Cost 164 GOLD. hands, and the coarser particles of stone and pebbles picked out. The miner now takes a large shallow basin, called a batea, and with a circular motion throws the dirt into the air, allowing the wind to carry off the lighter portions, and catching the remainder as it falls in the batea. This operation is repeated until what remains in the basin contains a large proportion of gold, when its further purification is effected by blowing with the mouth. This operation is similar to the old method of separating corn from chaff, and is conducted in very much the same way. Instead of using the wooden dish, two men sometimes take a hide, or blanket, in which they throw up the dirt for the purpose of exposing it to the action of the wind. The dry digger never goes very deep for his dirt, but unless it be rich in gold this method of operating cannot yield him remunerative returns, Instead of removing the surface earth, he frequently digs a pit six or eight feet deep, and then burrows after the pay dirt. This method of mining, which is not entirely confined to dry washings, is called coyoting, from the supposed resemblance of openings so made to the burrows of the coyote, or Californian wolf. A *- CHAPTER IX. VEIN MINING IN CALIFORNIA AND AUSTRALIA. QUARTZ MINING—TESTING GOLD QUARTZ—BATEA—HORN SPOON—ARRASTRE— CHILIAN MILL—STAMPING MILL—AMALGAMATING IN BATTERY—IRON BAT- TERY BOX —SCREENS— SINGLE CAMS—SEPARATION OF GOLD—BLANKETS—AMAL- GAMATED COPPER PLATES—CLEANING UP—SETTLING PITS—AMALGAMATOR— ATTWOOD’S SYSTEM OF AMALGAMATION—LOSS OF GOLD—CONCENTRATION OF TAILINGS—ROCKER—CONCAVE BUDDLE—BRADFORD’S SEPARATOR—EXTRACTION OF GOLD FROM SULPHIDES—BAUX AND GUIOD’S AMALGAMATOR—CHLORINA- TION PROCESS—ANALYSES OF CALIFORNIAN PYRITES—RETORTING—MELTING— TABULAR STATEMENT OF THE OPERATIONS OF THE PRINCIPAL CALIFORNIAN QUARTZ MILLS. THE processes employed for the extraction of gold quartz differ in no respect from ordinary mining operations applied to the working of regular mineral veins, and will consequently require no special de- scription. When the conformation of the country admits of working by means of a day level, it is driven in from some convenient valley in the neighbourhood of the vein, and the rock is obtained by stoping in the usual way. If, on the contrary, there be no facilities for this method of commencing the work, shafts are at once begun from the surface, either perpendicularly, so as to intersect the lode at some convenient depth, or, still more frequently, an inclined shaft is put down on the course of the vein itself. When the mine is worked by means of an adit level, the rock broken in the interior is trammed through it into the open air for subsequent treatment; but if the ex- traction be conducted by the aid of shafts, the auriferous quartz is drawn to the surface by skips or waggons running on inclined tram- ways In conuexion with a horse whim or steam-engine. In the case of very narrow veins some of the enclosing rock has frequently to be broken with the lode in order to afford room for the miner, whilst, in wide ones, it often happens that a portion only is sufficiently rich to pay the expenses of extraction and treatment, and the remainder is consequently allowed to remain in the mine. Sometimes also the 166 ; GOLD. walls of a vein, and particularly the foot wall, contain a sufficient amount of gold to make its extraction a matter of importance, and when this occurs a portion of the enclosing rock is necessarily exca- vated. In some veins the rock is, generally speaking, barren, contain- ing traces merely of the precious metal, the gold only occurring in paying quantities in pockets, at considerable distances from each other. In others the pay rock forms bands or streaks, running more or less parallel with the walls of the lode, and frequently separated from the non-productive portion by a distinct heading or band of country rock. Other veins are productive throughout their entire width, but seldom contain visible gold. These veins are not unfrequently lamellar in their structure, and contain thin interfoliations of slate parallel with their walls, as in the case of the Norambagua lode in Grass Valley. The most profitable leads are usually those which afford a large supply of rock obtainable at a cheap rate, and uniformly yielding an amount of gold in excess of the cost of extraction and treatment. In all mines, however, the produce is, to a certain extent, variable, and im the majority of cases the best rock occurs in shoots having a known inclination in the direction of the extension of the vein in length.* From the general irregularity of the produce, it is impossible to ascertain the average yield of vein-stuff without crushing and experi- menting on large quantities; but the most usual method of judging, approximately, of the value of rock, is to pulverise a small quantity and wash the resulting powder in a batea or horn spoon. In selecting the rock for this purpose, it is evidently of the greatest importance that it should represent a fair average of the vein or streak from which it is taken, and consequently several hundred-weights should be broken from the whole area of the exposed surface, taking care that every part be represented by samples of nearly equal weights. The whole must now be broken by a hammer on an iron plate, into pieces of about the size of walnuts. The resulting heap is then carefully mixed, by turning over with a shovel, and subsequently cut through the middle, so as to leave a trench through its centre, extend- ing to the floor on which it has been placed. The two sides are atterwards carefully scraped down, and removed as a representative sample on which the yield of the vein is to be estimated. For the * These pay shoots have generally the direction of the striz formed by dynamic action on the walls of the vein. . MAS Sod VEIN MINING IN CALIFORNIA AND AUSTRALIA. 167 purpose of a rough approximation this may be at once pulverised in a mortar or otherwise, and its contents judged of in accordance with the results obtained by washing. Where, however, greater accuracy is aimed at, and the original heap contained a large quantity of broken rock, at least a hundred-weight should be scraped down from the sides of the cutting, and this, after being further reduced to the size of peas, must be again cut through, and a sample of about four pounds obtained, by the means employed in the first instance, as the final sample. This is pulverised in a mortar, and the whole of it passed through a sieve of wire gauze, of forty holes to the lineal inch, after which it is ready for treatment, either by washing or assay. The most accurate results are obtained by carefully washing a four- pound sample in the batea (Fig. 22), which is about twenty inches in diameter, and two and a half in depth. Higa 22. BATEA. After having in this way concentrated the gold in about an ounce of sand and pyrites, this residue may be either subjected to assay, or the sulphides dissolved by nitric acid, and the gold extracted by amalgamation with a little mercury, which is subsequently volatilised, and the gold weighed. In either case, calculations are made on the four-pound sample, and when the residue’ has been subjected to fusion very accurate results are obtained. When amalgamation of the residue is resorted to, allowance must be made for the increase of weight arising from the impurities usually contained in the gold of the district. The spoon employed for washing small samples of pulverised quartz is made by cutting a large ox horn as shown at Fig. 23, and is generally about three inches in width and eight or ten in length. In this spoon about a pound of the powdered quartz is carefully washed, and from the results obtained the miner is enabled, by 168 GOLD. practice, to judge, with a certain degree of accuracy, as to the pro- bable yield of the rock. The quartz, after being broken from the vein, must be finely pulverised before the extraction of the gold it contains can be effected. Various contrivances are used for this purpose, but one of the simplest forms of apparatus employed is the arrastre. Fig. 23. Horn, sHowina Meruop or Curtine Spoon. Arvrastre.—The arrastre consists of a circular pavement of stone, about twelve feet in diameter, on which the quartz is ground by means of two or more large stones, or mullers, dragged continually over its surface, either by horses or mules, but more frequently by the latter. The periphery of the circular pavement is surrounded by a rough kerbing of wood or flat stones, forming a kind of tub about two feet in depth, and in its centre is a stout wooden post, firmly bedded in the ground, and standing nearly level with the exterior kerbing. Working on an iron pivot in this central post is a strong upright wooden shaft, secured at its upper extremity to a horizontal beam by another journal, which is often merely a prolongation of the shaft itself. This upright shaft is crossed at right angles by two strong pieces of wood, forming four arms, of which one is made sufficiently long to admit of attaching two mules for working the machine. The grinding is per- formed by four large blocks of hard stone, usually porphyry or granite, attached to the arms, either by chains or thongs of raw hide, in such a way that their edges, in the direction of their motion, are raised about an inch from the stone pavement, whilst the other side trails upon it. These stones each weigh from three to four hundred pounds, and in some arrastres two only are employed; in which case, a single mule is sufficient to work the machine. The following woodcut, P > 1 ee VEIN MINING IN CALIFORNIA AND AUSTRALIA. 169 Fig. 24, is a sectional view of a Mexican arrastre, as usually con- structed ; in which Ais the upright shaft; B, arms to which mullers c are attached ; and D, the central block of wood in which the lower bearing works. CY S SSS ARRASTRE. Some of the arrastres used by Mexican gold miners, and for the pur- pose of testing the value of quartz veins, are very rudely put together, the bottom being made of unhewn flat stones laid down in clay; but in a well-constructed arrastre, intended to be permanently employed, the stones are carefully dressed and closely jointed, and, after being placed in their respective positions, are grouted in with hydraulic cement. The charge for an ordinary arrastre is four hundred and fifty pounds of quartz, previously broken into pieces of about the size of pigeons’ eggs. ‘The machine is now set in motion, a little water being from time to time added, and at the expiration of from four to five hours ‘the quartz has become reduced to a finely-divided state, and more water is added, until the contents of the arrastre assume the con- sistency of tolerably thick cream. Quicksilver is then sprinkled over its surface to the amount of one ounce and a quarter for every ounce of gold supposed to be contained in the finely-divided rock, which is generally known, with a considerable degree of accuracy, from the results obtained from previous charges. The erinding is after this continued for another two hours, during which time the mercury is divided into minute globules, and becomes disseminated throughout 170 | GOLD. the mass, which should be of such a consistency as not to allow it to sink to the bottom, but be so held in suspension as to meet, and amalgamate with, all the particles of gold. At the expiration of this time the amalgamation is considered complete, and the process of settling the amalgam from the ground silicious matter is com- menced. Water is now let into the paste so as to render it very thin, and perfectly mobile, the mules being driven very slowly, in order to allow the particles of gold and amalgam to yield to the influence of their densities, and to sink to the bottom. After having in this way slowly agitated the mixture for about half an hour, the thin mud is allowed to run off, leaving behind it, in the bottom of the arrastre, the gold combined with mercury in the form of amalgam. Another charge of broken quartz is now put in, and the operation is repeated, time after time, until it is thought desirable to stop for the purpose of cleaning up. The length of a run, or the period which is allowed to elapse between one cleaning up and another, varies accord- ing to circumstances. In the roughly constructed arrastre, having a bottom of uncut stones laid in clay, the run is seldom less than ten days, and is sometimes extended to three weeks or a month. In this case the amalgam settles in the crevices between the paving stones, which have to be dug up, and all the sand and mud between them carefully washed. If, however, the machine be well constructed, and provided with a closely-paved bottom, the cleaning up is more frequently repeated, since the quicksilver and amalgam do not find their way so readily between the stones, but remain on the surface, from which they are easily collected in an iron vessel, for subsequent treatment by straining and retorting. The arrastre does its work slowly, and consumes a large amount a power in proportion to the quantity of rock crushed, but is an excellent amalgamator, and is often valuable for the purpose of testing newly-dis-. covered veins, and ascertaining their approximate yield. It is also the arrangement most commonly adopted by a miner, who, having found a rich pocket in his vein, is desirous of converting a portion of it into money, and of ascertaining whether it be likely to continue produc- tive, before incurring the expense of erecting more costly and compli- cated apparatus. A modification of the arrastre is not unfrequently employed for the treatment of pyrites separated from tailings by washing, and is generally considered to be well adapted for that purpose. The Chiltan Mill—The Chilian Mill consists of a vertical runner, VEIN MINING IN CALIFORNIA AND AUSTRALIA. 171 frequently of granite, revolving on a horizontal arm projecting from a perpendicular shaft, to which motion is given either by water or steam power, or by being attached to horse gearing. The basin in which the runner revolves is usually slightly conical, and may be made either of stone or cast iron. In this arrangement the grinding area is regulated by the difference of the circumference of the circles described on the bed stone, by the inner and outer edges of the runner. In the majority of cases the Chilian mill, instead of having only one runner, has two, one on each side of the vertical shaft; and in such mills they are fastened at different radial distances from it. The method of working rock by the Chilian mill is very much like that employed with the arrastre, but the former is now seldom used, as the latter is generally considered to be a more efficient machine. In order to show how expensive and inefficient this method of crushing is, we quote the following particulars relative to a Chilian mill, employed at the Silver Works of Constante, in Spain, given by Mr. Darlington, in an article on lg ite and grinding machinery, contributed by him to “ Ure’s Dictionary : ”— Diameter ofedgerunner .... . . .. 6G feet. Width = . sos + os + « Centre, 20 in. ; edge, 16 in. Weight s,, "s9 ceil Pek ai ane ee ATER LS OGL. Speed is “ most a.) «op Seb Seu Derminute, Diameter of interior circle. . . . . 4 feet. Size of stuff previous to its being gr eee . 10 holes to the lineal inch. 7 » afteritsleavingthemill . . 60 ,, i ae Quantity of stuff reduced per 10 hours. . . 350Ibs. mormeepower employed » 2. 6 we tk Stamping Mill—tIn addition to the arrastre and Chilian mill, there are various other contrivances for the reduction of ores, and the ex- traction of the gold they contain; but although a vast amount of ingenuity has of late years been expended on this subject, none of the numerous modern machines can in any way compare in efficiency with the ordinary stamping mill. This may he said to be the only apparatus extensively employed for the reduction of auriferous rock in all parts of the world, and, in spite of local peculiarities, differs but little in its arrangements from the same machine, as applied to the crushing of tin and lead ores in various parts of Europe. The stamping mill essentially consists of a series of heavy pestles, working in a rec- tangular mortar, each of which is alternately lifted by means of a cam, and subsequently let fall with its full weight upon the ore to be L72 GOLD. operated on, and of which, after being previously reduced to fragments of proper dimensions, a constant supply is introduced into the mortar, or battery box. When quartz mining was first practised in California, the lifters or stems of the pestles employed were made of wood, furnished with cast iron heads, attached by means of a wrought iron shank driven into the lifter, and secured by two strong rectangular bands of flat iron. In most mining districts in which these wooden stems are used, the lifting of the pestle is effected by a large wooden or cast iron drum, around the periphery of which cams are arranged in a spiral form, which, coming in contact with tongues, or tappets; fixed in the lifters, they are raised to a certain height, and, being suddenly released by the continuous motion of the axle, fall with their whole weight on whatever may happen to be beneath them. In California, however, another arrangement is employed for imparting motion to the pestles or stampers of a battery with wooden stems. Instead of a large cylindrical axle, a wrought iron shaft is made use of, and on this | are keyed a series of long curved cams, which enter mortise or slot holes, in the several stems, and cause them to be alternately lifted and released, precisely as in the case of the ordinary stamping mill, pro- vided with tappets and a drum axle. When wooden stems are made use of, they are usually about six inches square, and cut out of ash, or some other hard wood, having a straight grain. These wooden stems with square heads have, however, been almost universally superseded by the rotary stamp, with a round stem of iron, to which a circular motion is given by the friction of the cam in lifting, and which, being continued up to the moment of its release, is prolonged during its descent, thus imparting a grinding action to the cylindrical head at the moment of its coming in contact with the rock to be broken, The rotary stamp is said to be more efficient than the rectangular one, and to grind a larger quantity of rock in a given time ; but how- ever this may he, it is certain that the faces of the heads wear more evenly, and that a rotating battery requires less frequent repairs, than one made on the old principle. The battery box is generally com- posed of one solid casting, and usually receives either four or five stampers; when additional reducing power is required, other similar boxes are placed on the same line. In most instances, such batteries are arranged in sets of five stampers in each mortar, two of which are placed side by side in the same framing, ten stampers being thus set in motion by one shaft. Two five-stamp batteries, of a construction VEIN MINING IN CALIFORNIA AND AUSTRALIA. bby gs: frequently employed, are represented Plate II., fig. 1 being a back elevation, and Fig. 2 a transverse section; the iron rods A are the stamp stems, B the shaft, and c the cams. This shaft is provided at one end with a large pulley p, which is generally constructed of either kiln-dried wood on arms, inserted in a cast iron boss, and then turned off in place, or is built solid of well-seasoned planks on a bored boss, and, as in the other case, turned, after being keyed to the shaft. When several of these batteries are arranged in one house, the motive power is communicated, by means of a broad belt, to the intermediate shaft B’, which is fitted with pulleys corresponding to those on the shafts B, with which they are severally connected by belts. These belts, which are manufactured out of a combination of canvas and india- rubber, are, from the first motion to the intermediate shaft, sometimes as much as two feet in width. ‘The belts from the second motion to the shaft on which the cams are keyed, are made of a thinner material, and are from a foot to fourteen inches wide. The lift of the stampers varies from nine to twelve inches, but ten inches may be considered as about the average, and their weight, including the iron stem, varies from 550 to 900 Ibs. The order in which the several stampers, in- cluded in one box, strike their blows, in a five-stamp battery, is not always the same in all establishments, but in most instances the first blow is struck by the central stamp. This is followed by the outside one to the right, then by the second to the left, afterwards by the second to the right, and finally by the stamper on the extreme left of the series. The number of blows struck by each stamper is from sixty to eighty per minute. The first portion of the stamper @ is sometimes cast on to the stem, but more frequently it is fastened by wedges, and has a round aperture, in which is inserted the spill of the Shoe @’ firmly driven in or fastened by dry wooden wedges, which expand on coming in contact with water, and hold it securely in its place. The battery box is either of iron, cast in one piece, or its bottom alone may be of cast iron, and its sides of wood ; in which case the lower portion of it, together with the inside of the feed hopper, must be lined with sheet iron, half an inch in thickness, fastened by five-eighth bolts. Immediately under each of the stampers is placed a short cylinder of cast iron a’, which ig retained in its position, either by fitting into a circular bedding, in which it may be keyed by wooden wedges, or it is provided with a square flange, which, coming in contact with those of the other dies and the sides of the box, act as distance-pieces, by which it is kept in its proper position, These, 174 GOLD. and the shoes of the stampers, are, when worn out, readily repl by new, a considerable economy of time and money being the re: the paris worn out are merely coarse castings of chilled iron, withe any kind of fitting. The hole is for the purpose of forcing in a di above the spill of the shoe, and thus removing it when a new one is — required, whilst the hole z’ is employed in sie same way for getting off the boss from the stem. In Grass Valley, and some of the other oS more important mining districts, the boxes E are, almost without _ exception, composed of single iron castings; but in localities where __ amalgamation is conducted in the battery itself, the sides and ends are sometimes of wood, the bed alone being made of iron; and whenthis method of construction is adopted, two plates of amalgamated copper, one-eighth of an inch in thickness, are often bolted at 6 on either side of the row of stampers. The rock to be crushed is introduced by a shovel at c, and a plate of perforated sheet iron, fastened either in a wooden frame, or retained in its place between the two rectangular iron bands, tightened by cotters, is introduced before the opening d. The battery bed, whether entirely of iron, or consisting only of an iron bottom, with lined wooden sides, is firmly bolted to a block of Be wood, at least two feet square, and of which the dimensions, when ; ; very heavy stampers are employed, are even much greater. This — aa 7 either forms, as in the drawing, a portion of the general framing of __ the arrangement, or is now more frequently, to prevent jarring, made — “a quite independent of it. It is, however, essential that this portion of the structure should be well bedded on a solid foundation, and,if possible, rest directly on the bed rock. Occasionally quartziscrushed dry, but much more frequently water is admitted, and for this purpose _ a gas-pipe ¢ affords the necessary supply, which enters the boxes . through the branch pipes /, fitted with cocks for regulating the quantity introduced. The studs g, against which the cams come a | in contact, and by which the stampers are raised, are fitted me the iron stems by means of keys, which admit of their positions - being readily shifted, when rendered necessary by the wearing ge: the shoes. The props # shown in one of the batteries, but omitted in the other to avoid complication, are used for keeping up the stampers, - either when the battery box is being cleaned, or when a portion of the machinery is thrown out of action for the purpose of repair ; to do this they are successively pushed forward, so as to catch beneath the several bosses g, when lifted by the cams to their full height. Wher VEIN MINING IN CALIFORNIA AND AUSTRALIA. 173 not so employed the props are allowed to fall back out of the way of the stems, as shown in the sectional drawing. The size of the apertures in the gratings or sieves at d, differ in accordance with the fineness of _ the gold contained in the rock treated, and is also, to a certain extent, varied in conformity with the particular views of the superintendent of the mill on that subject; but it is evident that with very small apertures the amount of quartz crushed, all other conditions being equal, will be less considerable than when a coarse screen is employed. The size of grating commonly made use of in some of the best mills in the Grass Valley district ,is shown Fig. 25, which is known as “ No. 8.” Fig. 25. STAMP GRATE, witH Rounp Ho uss. (Full Size of Apertures.) In order to combine strength with the largest possible open surface, the apertures are sometimes made of an oblong form, and arranged as in Fig. 26. Stamp GRATE, WITH OsLone Ho tes. (Full Size of Apertures.) In some establishments these gratings are fixed perpendicularly, as seen in Plate II. ; but more generally they are shehtly inclined outward, and this arrangement is evidently attended with certain advantages. 176 GOLD. When the grating is placed perpendicularly, a particle of quartz or other pulverised matter, splashed against the screen by the fall of the stampers, can only pass through it in case of being projected directly through one of the openings, and should it strike against a portion of the solid plate between the holes, will run down with the water on the inside, and again settle in the battery box. If, on the contrary, the erating be placed at a considerable inclination outward, as shown Plates III. IV. and VIIL, a particle of pulverised rock, which has not been projected immediately through the grate, may, on running back with the water over its inner surface, pass through one of the apertures and escape into the trough on the outside of the battery. In all machines of this description, it is of importance that each particle of the rock operated upon, should escape from the action of the stampers, as soon as it has become sufficiently reduced in size, and with this view the grate surface is in the Californian mills extended as much as possible, being generally made of nearly the full length of Fig. 27. Fia. 28. Iron Battery Box, the battery box. With a view of supporting the grating, and protect- ing it against injury from the impact of the water dashed against it by the falling stampers, the sheet iron plate is externally strengthened by the application against it of some thin iron bars, When the high cast iron mortar is made use of, which is now generally the case, it has the form represented Figs.,27 and 28, VEIN MINING IN CALIFORNIA AND AUSTRALIA. jr, which the first is a transverse section, and the second a front eleva- tion; the dies are fitted on the bottom A, aud the quartz fed through the opening B, whilst the screens are fastened, by nails or screws, to a frame which is firmly secured in grooves provided for its reception at the ends of the mortar, and by two lugs at the bottom of the opening C. In some cases, instead of employing a double cam, as seen in Plate II. fig. 2, a single one is made use of. This has generally the form shown Fig. 29, and possesses the advantage of allowing the axle to be placed nearer the stamp stem than it can with any other cam, and also that by its use a greater number of blows can be struck per minute, without danger of breakage. Fig. 29. SINGLE CAM. The auriferous material having been reduced to the state of a finely- divided powder, it becomes necessary to provide means for the con- centration and separation of the gold, which is more or less perfectly effected by an almost infinite number of different contrivances, varying slightly in their details in almost every establishment that may be visited. However much the processes employed may differ in this respect, only two decidedly distinct systems are now practically in use in California, viz. amalgamation in the battery ; and crushing without the use of mercury, amalgamation being subsequently effected by means of appliances specially designed for that purpose. Amalgamation in the Battery—When this method is adopted, the batteries are often provided with amalgamated copper plates d (Plate II. fig. 2), about five inches in width, extending the whole length of he: box ; one on the feed side and the other at the discharge, the latter being ore by the sheet iron lining of the feed hopper, | N 178 | GOLD. and each having an inclination of from forty to forty-five degrees towards the stampers. When these are not employed, spaces ae the accurmmiaae of amaleam are allowed between the dies and the sides of the box, and vertical iron bars are placed inside the gratings, between which the hard amalgam is found to collect. The copper plates are covered with mercury, by means of a rag dipped in dilute nitric acid, with which quicksilver is rubbed over the surfaces to be coated, in the same way as on those used in ordinary sluices. Quicksilver is also sprinkled into the boxes, by the feeder, at intervals of about an hour, and in quanti- ties varying with the richness of the rock operated on. One ounce of gold requires for its collection about an ounce of mercury; but when the gold is in a finely-divided state, the addition of another quarter of an ounce of this metal is thought advantageous. The proper proportion is, however, readily ascertained by closely watching the discharge. If any particles of amalgam which may pass through be hard and dry, a little more quicksilver must be introduced ; but if, on the contrary, they be soft and pasty, or globules of mercury make their appearance, the supply in the battery must be diminished. When the proportion of mercury has been properly adjusted, the amalgamation of the gold is very completely effected, except in cases in which the ores contain large quantities of lead or antimony, and have been previously burned for the purpose of expelling their more volatile constituents, by which treatment the particles of gold often become coated in such a way as to interfere with their combination with mercury. When the proper proportion of quicksilver has been regularly introduced, and the rock contains coarse gold, from sixty to eighty per cent. of the gold saved is caught in the battery; but when, as in the case of some of the ores of Nevada, the gold is in a very finely-divided state, and is associated with ores of silver and other sulphides, the results obtained are less satisfactory. The alloy resulting from the treatment of such ores contains silver, and in some cases affords from 300 to 400 thousandths only of gold, often producing a spongy amal- gam of a dark colour, made up of an aggregation of numerous finely- divided particles. Kustel is of opinion that this effect is partially due to the presence of manganese, but it appears difficult to understand how this substance should influence, to any important extent, the combina- tion of gold and mercury. ‘This amalgam is exceedingly light, and is, therefore, difficult to collect, either by riffles, copper plates, blankets, or any of the other appliances commonly employed for the purpose. — Nenbery & Alecander Lith 43 Castle S¢Holborn Id STAMP BATTERY STAMPS 550) Ges: WET CRUSHING & AMALGAMATING IN BATTERY. —_ . — Scale, %% Inch — | Feet Keltrence A Starnp (tliers or sterns a. » heads a shou a dies Be CGarm-shatt B. Second metiov shatt 6 Amalganiuted copper JHhates C. Cams © heed: hopper PD. Dring pall d Crating E battery boxes or collers ef Water pupes CG. anklet board g Losses by which stamps are ltted he. Props for stampirs wal Dritt: holes. E&EN.Spen 48,Charing Cross London PLATE ff VEIN MINING IN CALIFORNIA- AND AUSTRALIA, 179 When, therefore, ores contain much lead or antimony, amalgamation in the battery is not to be recommended, since this spongy amalgam is more difficult to retain than the most finely-divided gold, and a large proportion of it floats off’over the blankets, riffles, or copper plates, which may be arranged for the purpose of arresting its progress. There is, besides, no evidence that battery amalgamation possesses, under any circumstances, a decided advantage, for gold ores not asso- ciated with sulphide of silver, over stamping without the use of mercury, and in some of the most productive gold districts it is seldom resorted to. In order to collect the particles of gold and amalgam escaping from the battery box, various ingenious contrivances are employed ; but as these arrangements differ but little in their details, whether mercury be employed in the battery, or the amalgamation entirely effected after the escape of the pulverised material through the screens, we will proceed to describe the system generally in use in the northern quartz mines, in which the various arrangements are of the most improved description. Blankets—At Grass Valley, which, from the richness of its quartz veins and the excellency of the machinery employed for the reduction of the ores, may be considered as the head-quarters of quartz mining in California, the rock is generally crushed without the introduction of quicksilver into the mill. In this district the sand and water issuing from the battery are conducted over blankets spread. on the bottoms, and lining the sides of shallow troughs or sluices, inclined at an angle of from three to four degrees with the horizon. Beyond the blankets there are, in most cases, riffles or amalgamated copper plates, which are again followed by some contrivance for collecting the pytites remaining in the tailings. At the further extremity of this system of appliances there is sometimes a long tail sluice for the purpose of arresting any auriferous material that may have escaped being caught by the other arrangements. The blanket boards are from fourteen to sixteen inches in width, inside measure, and three inches in depth, being so laid, with a recular longitudinal inclination, that transversely the bottom is perfectly level. It is necessary that this should be carefully attended to, in order that an equal depth of water may, when the mill is in action, flow over every portion of its surface, and thus prevent the occurrence of a rapid current on one side, whilst an accumulation of sand is taking place on the other. The blankets employed are, for the most part, N 2 180 GOLD. woven expressly for the purpose, of coarse grey wool, and are made of such a width that, when laid in the troughs, and fitting closely over the bottom and sides, they hang down about six or eight inches be- yond the top of the woodwork ; and in order that they may be readily adjusted, and that no portion of the stream may flow down behind them in the angles, a triangular piece of wood is sometimes fitted into the corners made by the junction of the bottom and sides. The section of one of these troughs (Fig. 30) shows the position of the blanket when fitted in its place. Fie30: SECTION OF BLANKET BOARD. In laying these blankets in their troughs, they are so placed as to overlap each other, like tiles on a roof, in order that the water flowing from one may run directly over the other, being prevented by the lap given to them, from finding its way between the blankets and the bottom. The troughs are also themselves made in two or more lengths, and are so arranged that the water in passing through the first, falls into the second, from a height of about three inches. The general disposition of the batteries and blankets in a well- arranged Californian establishment, will be understood by reference to Plate III., in which fig. 1 is a sectional elevation, and fig. 2, a plan of the apparatus. The battery box A is fitted in front with a water-tight wooden trough B, running its whole length, and provided with an aper- ture b, opening on the blanket board c, and with a second aperture 0’, at its inner end, which, like the first 6, can be closed by a small wooden slide, or by placing a bit c* plank before it. Immediately before the centre of each battery is placed a blanket board c, and, between each pair a third c’, to be used when either of those on each side of it is thrown out of action, for the purpose of removing the blankets. The troughs © and c’ are sixteen inches in width, three inches in depth, and have a length of twelve feet; these empty themselves into the troughs D D’, having the same width, depth, and inclination, but only nine feet in length. When the batteries are in their normal VEIN MINING IN CALIFORNIA AND AUSTRALIA. 181 state of working, the water and crushed ore flow from the apertures 8, passing through the troughs c, and running over the surface of the blankets with which they are lined; a large portion of the gold and iron pyrites thus becomes entangled in the fibres of the wool, and remains behind, whilst the lighter particles of quartz are carried off by the force of the current, and escape at the lower end of the troughs. If this were allowed to go on without interruption, the fibres of the- blanket would soon become so charged with the heavier fragments of crushed ore as at length to cease to act, and the whole of the products of stamping would pass off and be lost. To obviate this, the blankets are frequently washed up, and are then again ready to arrest any particles of gold or pyrites with which they may come in contact. In well-managed mills the blankets at the upper end of the arrange- ment are now washed every fifteen minutes, and this operation is conducted as follows:—The orifice 8, opening from the trough B, on one of the blanket boards ¢, is closed, and the aperture 0’, communi- cating with the board c’, standing between the two batteries is opened. This has the effect of leaving the first trough c without water, whilst the stream which before flowed over it is directed through the central trough oc’, The blanket over which the current is no longer flowing is now taken up, being at the same time so folded as to prevent the loss of any portion of the adhering matter, and then taken to a rect- angular tank prepared for the purpose, where it is carefully washed, and again laid in the trough from whence it was taken. The flow of water and sand from the battery is now cut off from c’, and admitted into its original channel; the same operation being repeated on the trough belonging to the other battery. When the blankets in the intermediate trough require changing, it is done whilst the others are in use. The blankets at the upper end of this system only, are changed so frequently as above mentioned; whilst those on the lower boards D D’, often remain some hours without being washed up. In some mills instead of the intermediate trough o’, there are two blanket boards to each battery, in which case one is being clecned up whilst the other is in operation. The cistern, or tank, Fig. 31, in which the blankets are washed, is always situated in the immediate proximity of the troughs containing the blankets requiring most frequent washing, and is generally four feet in height and four feet square at the top, but somewhat smaller at the bottom. On one of its sides is an inclined ledge on which the blankets are rolled after washing, and when again laid down they are 182 GOLD. rapidly unrolled from the bottom of the trough upwards, so as to fall directly in their places. Section OF WaAsHING TANK. Sometimes, although rarely, ox hides have been employed instead of blankets, and are placed in the troughs with the grain of the hair against the current, but these are only used in mills of very primitive construction. Sheep skins have also occasionally beeu tried, but these, like ox hides, make bad substitutes for blankets. In some mills, a small stream of clear water is admitted into the troughs at the head of the blankets, for the purpose of rendering the mixture of sand and water issuing from the battery so dilute as to enable the gold and pyrites to settle with greater facility, and this is by some muill- managers considered advantageous; but when the volume of water passing through the troughs is thus increased, their inclination should be made proportionately less considerable. In the majority of cases the gold retained in the battery, together with that collected on the blankets, will represent at least nine-tenths of the total amount obtained from the rock under treatment; but there is, nevertheless, a notable quantity of the precious metal which passes over the blankets, and of which it is desirable to recover the largest possible amount. Amalgamated Plates—With this object amalgamated copper plates, often arranged in the form of riffles, are employed, and at the end of these are cisterns or tyes for the collection of the auriferous pyrites, which is subsequently concentrated and treated for the gold it encloses, At some of the mills in Grass Valley, after running over two blanket boards, respectively twelve and nine feet in length, and having an inclination of three and a half degrees, the water 1s conducted through troughs EX’ (Plate III. fig. 2) eleven inches wide, of which the bottoms are formed of amalgamated copper riffles, and which have the same VEIN MINING IN CALIFORNIA AND AUSTRALIA. 183 inclination as the blankets. From this, the current passes through troughs F F’ set with a less inclination, and of which the bottoms are also formed of amalgamated plates, whilst at the end of these are two reservoirs for the retention of tailings. The plates ¢, forming the bottoms of the riffles in the troughs E EF’, are made so as to slide easily in and out of their places for the purpose of being cleaned, or re- amalgamated, and are about eight inches in length. The riffle plates in the troughs F F’, are also movable, although con- siderably longer than in those above them ; but it is probable that, if instead of contracting these spouts they had been widened, or still better, if two of them had been employed to carry off the current flowing from each of the riffle boxes E E’, and a little fresh water ad- mitted for the purpose of diluting the mixture of water and pulverised ore, the fine particles of gold would have had increased facilities for settling and becoming attached to the surface of the amalgamated plates. Cleaning up, &c.—The stampers, except when undergoing repair, or stopped for the purpose of cleaning up the gold which accumulates in the battery boxes, are kept constantly at work day and night, the fre- quency with which the boxes are cleaned of course depending on the richness of the rock operated on. Generally speaking, however, the cleaning up of the battery box takes place at least every week, and often more frequently, particularly when mercury is intro- duced during the process of crushing. When quicksilver is used in the battery, a very large proportion of the gold obtained is taken from it in the form of amalgam, and even when this metal is not introduced the cleaning up of the battery affords a considerable percentage of the produce, which accumulates in the cavities around the dies, in the form of metallic spangles. The coarser the gold in the rock treated, the larger will necessarily be the percentage of the total produce retained in the battery. Instead of blankets, employed as above described, Brunton’s separators, with revolving woollen cloths, have been sometimes used ; but these not having been found efficient, have been generally abandoned. Settling Pits—When settling pits are used for the purpose of col- lecting the tailings for subsequent treatment, it is necessary that at least two of them should be provided, so that whilst one is being filled the other may be cleaned up, but in many cases a long pit resembling a Cornish tye is substituted, which, instead of being allowed to fill, and then emptied, is constantly under the superintendence of a lad, 184. GOLD. who shovels the sand out of it as rapidly as it is brought in by the current, thus causing an amount of agitation, resulting in a further portion of the lighter particles flowing off, and conducing to a greater degree of concentration in the product obtained. It is, moreover, necessary that every mill should be furnished with at least two tanks for washing up blankets, so that one may be ready for use whilst the other is in course of being cleaned up. In some mills, also, the tailings, instead of being allowed to accumulate in a reservoir or tye, prepared for that purpose, and from which they are subsequently removed by manual labour before being submitted to further treatment, are con- ducted directly into concentrating apparatus, from the end of troughs lined with amalgamated plates. Amalgamator.—The separation of gold from the matters caught on the blankets, and collected in the washing tanks, is generally effected in California by a very simple piece of apparatus, introduced, many years since, into the northern mines by Mr. M. Attwood, Figs. 32, 33. This machine consists of two wooden rollers A, eight inches in diameter and two feet in length, furnished on their circumference with numerous small flat knife-bladed pieces of iron arranged around them with their edges at right angles to the axes of the cylinders, and working in cisterns containing mercury ; above these rollers, which are set in motion by the pulleys B, over which a belt is stretched go as to cause them both to revolve in the same direction, but contrary to that of the water flowing through the apparatus, is a hopper ©, for receiving the sand to be washed. Another pulley D, is connected by a second belt to a rigger keyed on a small shaft fixed in the roof of the mill house, and communicating motion to the whole arrange- ment. Below the cylinders 4, is a riffle board £, having an inclination of seven degrees from the horizontal, and generally covered with plates of amalgamated copper, which can be readily slipped out for the purpose of having the gold amalgam, which may become attached to them, removed. When copper plates are not employed for this pur- pose, the steps of the riffle are reversed and charged with mercury. To use this apparatus, some of the sand taken from the cistern in which the blankets have been washed, is placed in the hopper, and — a small stream of slightly-warm water allowed to play on it from c’, in such a way as to gradually wash it under the spiked cylinders A, and from thence over the amalgamated riffle board g.* This riffle board is * The use of warm water is found to facilitate amalgamation, particularly during cold weather. ; ) S & RIFFLE AT | | LEY &¢. trom i est 2 | ee — It PLATE UT ory Ss eeMe OF 3B LAN KES © & orhtenih secs REFERENCE. EMPLOYED AT lees Battery bo or Coffer. Bee Fea CRASS VALLEY &c. Pee Coen ptortlan hem boarde C. . 5. __ Openings on blanket board C’ C._ Blanket boards C! _ Intermediate blanket board. D._ Second blanket boards. 1B ak gh D! _ Second intermediate blanket board. EEFF Amalgamated copper riffle. ee. Mevable riffle plates Llerattion Scale Valach to a Focet. Newbery & Alewander Lith $3 Castle S*Holbon VEIN MINING IN CALIFORNIA AND AUSTRALIA. 185 usually nine feet in length, is divided into several channels, and has at its end a cistern for retaining the pyrites and other matters, which, not combining with mercury, escape amalgamation. As the material operated on in this machine is always highly auriferous, and consequently very valuable, great care is taken to exactly regulate the feed at the upper end, and to keep the surface of Fig. 32. nn (i mu Ww): I rey — | | | a! PLAN oF AMALGAMATOR. the riffles perfectly bright, and clear of any accumulation of pyrites. A boy is therefore stationed at the riffle board, who skims off any scum or impurity which may accumulate on the surface of the plates, and collects it for subsequent treatment in small cast iron arrastres. The sulphides deposited in the tank at the extremity of the riffle board are sometimes ground with mercury, in a Varney or Wheeler pan, and, after thus extracting as much gold as can be so obtained, they may, if they 186 | GOLD. still retain a sufficient amount of gold, be drawn off, and, after settlin are collected and sold for treatment by smelting or chlorination. — In many establishments, however, the pyrites from the tanks at the end of the amalgamators, undergoes no further treatment, but is col- lected and sold as an auriferous sulphide of iron, or it may, previous to being sent to market, be subjected to a simple washing in a rocker, or otherwise, for the purpose of eliminating the sand. The annexed diagram shows the various processes to which gold-bearing quartz is subjected in the neighbourhood of Grass Valley, and Sx at a glance the series of operations which the rock undergoes in some of the best mills in that district. | | | BATTERY ( Gold te ——_——____.__ eee | Pyrites to Wasling Tank, Tank. ———- “SIO URIG = | a ee 2 i) - | \ i : = > Amalgam to aes 44 v ; AS al € = 3 5 : ‘ Skimmings fot irs rast] Amalgam to—» be Westie { Retort Got to— bY Scum, &e. j J & -Amalgam to —— cues ERS E | Pan os ———> Amalgam to ———_______~ z ) : ee Residues to— ————~ 3 Market : / y |? Pyrites &e. ~ Concentrator \ Pyrites to— 2 (Gssebet a Riae mm wR a 2 B 3 rv ou i Bhai’ Bs ex <—odInTg TEL It must, however, be understood, that there are scarcely two mills in which the various manipulations are conducted in precisely the VEIN MINING IN CALIFORNIA AND AUSTRALIA, 187 same way, and consequently in the chart of operations mere non- essential differences have been disregarded. Attwood’s System.—Mr. M. Attwood, of San Francisco, has recently ~ designed an arrangement, of which a drawing is given, Plate IV., for saving the gold issuing from a stamping mill. In this Plate, fig. 1 is a sectional elevation ; fig. 2, plan; fig. 3, lower end of tyes ; and, fig. 4 end of steam chest. | In this arrangement Mr. Attwood does not make use of blankets, but the ground ore issuing from the battery screens, flows directly on to the amalgamator, where it is gently stirred by the action of the cylinders A, turning in the direction indicated by the arrows, and then passes on to a riffle board B, covered by amalgamated copper plates, where a great portion of the amalgam, escaping from the cast iron mercury boxes a, will be collected. In order that the mercury in the boxes under the rollers may not become too cold, and its affinity for gold be thus rendered sluggish, they are cast with a double bottom, through which a current of steam can be made to pass, and which is easily regulated by an ordinary tap. From the riffles B, the ground material passes into the tye o, of which the bottom is inclined at a considerable angle, and which is provided at the lower end with a slot c, for regulating the depth of water within it. This is done by means of the stops ¢’. In order to catch any globules of soft amalgam or mercury, which may become detached from the surface of the amalgamated plates, a small cistern D, running the whole width of the riftle board, is provided; in this is an agitator d, turning in the direction indicated by the arrow, and which constantly keeps the box; to the depth of its arms, free from accumulations, so as to form a depression in which the mercury and amalgam may become deposited. | To use this apparatus, one of the stops c’ is placed in the slot ¢, and the mill started in the usual way ; the sand which has passed through the amalgamator soon reaches the tye, and the heavier portions begin to accumulate behind the stop, whilst the lighter particles are carried off by the current. The removal of the light sand is facilitated by gently sweeping the surface of the deposit upwards against the stream with a light broom, a boy being stationed there for that purpose ; and when the pyrites which is deposited, accumulates to the height of the top of the first stop, another is inserted, and the operation carried on continuously. When one of the tyes has been filled in this way, the tongue E is so turned as to direct the sand and 3 188 GOLD. water into the other, Shh is thus filled whilst the first is being emptied. It is evident that by this means the pyrites will be collected in the tyes in a very concentrated form, and that the amount of labour re- quired is but small; we have, however, never seen this apparatus in operation, and are without any precise data showing its efficiency, as compared with the blankets and riffles now in general use. System employed in Australia—Port Phillip Company.—Mr. Bland describes the treatment to which the auriferous quartz is subjected, as follows :*— “The quartz when brought to the surface is separated into two lots. The small size is tipped into a large hopper, and from thence drawn and delivered, direct, to the stamps, and the larger lumps are sent to the stone-breaking machines to be reduced to a size suitable for the stamps. ‘Two of these machines are in constant use, working on an average about ten hours per day. Each machine will break about eight tons per hour when in good order, at a cost, including wear and tear, of about 10d. per ton. They are driven by a shaft from one of the battery engines, and take about twelve horse-power to drive the two. The number of stamps at work is eighty, as follows :—Fifty-six heads of about six ewt. each, including lifter and tongues, driven by one twenty-four-inch engine, giving seventy-five blows per minute, taking about one horse power per head, and crushing an average of about two tons four cwt. per head, for twenty-four hours ; twenty-four heads of about eight ewt. each, including lifter, &c., dried by a twenty-four- inch engine, giving seventy-five blows per minute, taking in the agere- gate about thirty horse power. These stamps crush about four tons per head per diem, and they have a larger proportion of the small material sent to them. The average quantity of quartz crushed per : week, of five days, is about 1,130 tons. “The following is a return of quartz crushed for the twelve months ending September 1865 :— 54,413 tons . . 20,5960z.10dwt.12gr. . . 7 dwt. 13gr. “The gold above mentioned was collected in the following way :— Lo stamp beds ch, aan pak oO dae Mercury sboxés:).. ei Wee cr aes p..e. Blankets! 2S SA er Oe * The quartz, at the works of the Port Phillip Company, is stamped much coarser - than in California. The screens have only ten holes to the lineal inch, and hence the larger amount got through within a given time. PLATE SL. < Qa =7 oma ——= we CLLL1S 177 77m , ZZ BSSSSSSSSSS ESS SS as 43, Castle S¢ Holborn. Newbery & Alexander, Lith, ; + PLATE IV. ae ATTWOOD'S AMALCAMATOR. Reterence A Agitatung rollers with iron blades a. Mercury Troughs B. Copper Riffles C.C. Tes. : c. Apertures at bottom of Fes y c.c. Stops for do. do. D. Trough tor collecting Mercury & Amalgam j a. Agitator wu Trough Pay 2". . Vf EE. Tingue tor directing course of tailings into hres © & C zz Ce — Elevation Figs AG Tl Cc | |____t TTT tL Se il C ! IE sae —= = ——— = Son Cec OmewO iu —— a oo | i— —ail ff etter — ir —— —_——— —_—_————_|___— 506 Scale fa Inch to a Siete. = 2 7 : Newbery 4 Alewander, Lith. 43, Castle S¢Holborn. | & F.N.Spon.48,Charino: Cross.Londox VEIN MINING IN CALIFORNIA AND AUSTRALIA. 189 “The quantity of water required to work the stamps efficiently is about eight gallons per head per minute, which is 921,600 gallons per diem. The tailings on leaving the stamps run into settling boxes, where the current is checked, and the heavier material settles. These boxes are cleaned out every few hours, and the material sent to the buddle, where it undergoes a further concentration, and is dressed up to an average of three or four ounces of gold to the ton of material. This is then sent to the roasting furnace, and afterwards ground in Chilian mills with mercury, and an average of about eighty-five per cent. of the assay contents of the gold is thus extracted. The cost of operating on the pyrites, including the buddle, roasting, grinding, loss of mercury, &e., averages about 2/. 14s. per ton, or about 17. per ounce of gold obtained. | “The expense will diminish as the quantity of pyrites increases, and improves in richness. “The quantity of quartz crushed, and yield of gold from the com- mencement of the Company’s operations in 1857 to the 31st July, 1866, was as follows :— Quartz crushed. Yield of Gold. 308,661 tons. 180,723 oz. 15 dwt. 10 gers. Equal to six tons of 2,000 Ibs. each,” Loss of Gold, &e.—In California the tailings escaping from the last of the appliances employed for the separation of gold, are never care- fully and regularly assayed, and consequently it would be impossible to arrive at a correct estimate of the losses resulting from the imper- fections incident to the modes of treatment adopted. It would, how- ever, seem that there is comparatively little difficulty in effecting the separation and amalgamation of the free gold, and that the principal losses attending the working of ordinary gold quartz, arise from the escape of small particles of this metal enclosed in pyrites, and which the concentrating apparatus fails to collect. Nevertheless, in some instances the surface of the gold would appear to be coated with a thin glaze of silica, or some other substance which protects it from amalga- mation, and in such cases its combination with mercury can only be effected by grinding in a pan, arrastre, or some similar contrivance. The only data relative to this subject which we have been able to pro- cure, have been obtained from the officers of the Port Phillip and Colonial Gold Mining Company, at whose establishments, in Australia, the tailings are regularly sampled and assayed, and found (see table, 190 GOED, page 116) to contain on an average about 2 dwt. of gold, of which some portion is again recovered from the washed sulphides, by roasting and grinding in Chilian mills. The weight of the stampers employed in the Californian mills differs considerably, and, as a natural consequence, the amount of work done by each in a given time varies in nearly the same ratio. In the neighbourhood of Grass Valley, heavy heads are almost univer- sally employed. At the North Star works, the stampers, including the stems or lifters, weigh 9 cwt. and crush weekly 132 tons of quartz, or very nearly two tons each in twenty-four hours. The stampers at Allison Ranch are of the same weight, and perform the same amount of work. At the Eureka mill the stampers weigh 840 lbs. and are esti- mated to crush about two tons each in the course of the twenty-four hours. The table at the end of this chapter, constructed from data collected by Mr. Ashburner in 1861, gives the cost of stamping, weight of stampers, loss of mercury, and many other particulars re- lating to the various quartz mills then at work in California, since which period the cost of treatment has been somewhat reduced.* Concentration of Tailings——In the earlier days of quartz mining, the pyrites and other metallic sulphides were generally allowed to escape with the earthy and silicious portions of the vein-stuff, and a considerable loss was naturally the result, although an attempt to extract the gold which they enclose was sometimes made by roasting the quartz in kilns or heaps, before subjecting it to the action of the stamping mill. This was, however, found to be of little prac- tical advantage, and quartz is therefore now stamped without any kind of preparation beyond that of spalling, or breaking it into frag- ments of a convenient size, but much care is devoted to recovering from the tailings the largest practicable proportion of auriferous material. The machinery and contrivances employed with this object are of the most varied description, and it would be therefore impossible to attempt a description of the whole of them, and we shall consequently * An interesting paper has been recently published by the Geological Survey of California, entitled ‘‘ Mining Statistics, No. 1. Tabular Statement of the Condition of the Auriferous Quartz Mines and Mills in that part of Mariposa and Tuolumne Counties, lying between the Merced and Stanislaus Rivers, by A. Rémond.”— Philadelphia, 1866. From this it would appear that the cost of milling at the present time is lower than when Mr. Ashburner compiled his tables ; but the information afforded being of a comparatively local character, we abstain from making extracts. VEIN MINING IN CALIFORNIA AND AUSTRALIA. 191 confine ourselves to noticing such as are most commonly made use of in the best-conducted establishments. Rocker—tThe rocker consists of a trough about twelve feet in length, fourteen inches in width, and ten or twelve inches deep at the sides. In appearance this contrivance is not unlike a school form, of which the top constitutes the bottom of the trough, and of which one leg is shorter than the other, so as to give a slight inclination to the machine. The two legs, which are very short, are rounded at bottom, like rockers, and kept in their positions by articulations which allow of the arrangement working from side to side, this motion being com- municated to it by means of a crank, or eccentric and small sweep rod, attached to a pulley, driven by a narrow belt. The trough thus formed is rocked at the rate of forty-five strokes per minute, with a one-inch throw, and is furnished with an end at the higher extremity only, the other remaining open, and forming a spout for the escape of water and sand. Water is admitted at the upper end by means of a flexible tube, and the bottom is lined with sheet iron to prevent wearing. To use this machine, the workman stands at one side of it, near its upper end, and after having turned on the supply of water, he throws in a few shovelfuls of the sand, which has been collected either in the settling pits or tyes. The rocking motion, together with the stream of water, aided by the judicious use of the shovel, causes the lighter silicious particles to be carried off, whilst the heavier pyrites remains in the trough of the rocker. This is removed by the shovel, and another charge of unwashed tailings introduced, the opera- tion being carried on continuously in the same way. This machine washes the pyrites very clean, but appears to allow too large a pro- portion of it to be carried off in the final tailings. Concave Buddle—This apparatus, invented by Mr. Hundt, a Prussian engineer, and patented in this country by a Mr. Borlase, has been successfully introduced at the Port Phillip Company’s works in Victoria. This arrangement possesses the advantage of affording a large working area at the head, and at the same time effects a better separation of the waste than can be produced by round buddles of the ordinary construction. Also, when the lighter portions of the tailings have become separated from the heavier near the periphery of the circle, the area over which they are distributed gradually diminishes, which by increasing the rapidity of the flow, enables them to be more readily and effectually carried off. In Australia this apparatus is employed for concentrating tailings from which a large 192 | GOLD. proportion of the gold has been previously extracted by the usual . appliances. The woodcuts, Figs. 34, 35, represent a plan and section of one of the best forms of the concave buddle. Fie. 34. SS Q SSS $y SECTION OF CoNcAVE BUDDLE. The spout bringing in the mixture of water and sand is represented by A; Bis the outlet for carrying off the earthy impurities, or final tailings ; Cc, shaft communicating motion to the buddle arms d, the dis- tributing launders ¢, and pipes g’ attached thereto ; f£ pipe for supply- ing clean water to the annular cistern g, from whence it passes by the pipes g’ with rose apertures at the ends, and serves to dilute the mixture of water and tailings discharged by the launders e, on the annular in- cline at the periphery. The whole of this arrangement revolves: on the shaft D; 2 is a circular pit, into which the final tailings fall, previous to being carried off by the channel B. To the wooden bars k, are attached pieces of canvas which sweep over the surface of the stuff deposited in the buddle, and keep it even and free from ruts. The tailings, entering the receiver h, are distri- buted at the periphery of the buddle through the four launders e, which at their extremities are turned at right angles to the direction of their motion, when in action; and at the same time clean water is distributed by the apertures pierced in the terminations of the pipes g’. VEIN MINING IN CALIFORNIA AND AUSTRALIA. 193 The speed given to this arrangement of arms, launders, and pipes, | revolving on the shaft D, varies in proportion to the state of division of the sands to be treated; when these are rather coarse, the machine may make from six to eight revolutions per minute, but when very fine stuff has to be dealt with, the speed is considerably increased. The influx of tailings and water must be regulated in accordance with the speed of the arms and the density of the stuff operated on; and although no very definite instructions can be given with regard to this subject, a short trial of the apparatus will enable any intelligent workman to make the necessary adjust- ments. The bed may be from twelve to eighteen feet in diameter, and have an inclination of from six to nine inches from the edge to the centre. NINA BN igi / im gS od, il) p= y PLAN oF ConcAve Buppte. At the Port Phillip Works, the tailings cleaned by machines of this description are subsequently roasted, and passed through Chilian mills; but where, as in California, the enriched pyrites has to be . transported to considerable distances, it would require to be more than ©) 194. » “GOLD, once passed through the machine, or, after being once buddled, the heads might be further enriched, either in the rocker, or by a hand buddle or shaking table. A buddle of this kind can be filled in about four hours, and forms an excellent apparatus for enriching ores with but little waste. If it be intended to dress sulphides directly from the riffles, so as to render them almost entirely free from silicious matter, the first heads will require to be re-washed at least once, and the second heads twice; but when this is done, it is necessary to be provided with other buddles besides those which first receive the tailings direct from the riffles, and which will be constantly in use for that purpose. When the tailings to be washed are not conducted directly from the blanket boards, but are taken either from tyes or the heads of other buddles, they are charged with a shovel into a hopper con- nected with a circular sieve, working in water, which discharges into the spout A. ' Bradford's Separator—vVarious modifications of this machine are employed in the mines of Grass Valley, and particularly at the Norambagua mill, about three miles south of the town. This machine is nothing more than a very compact form of the shaking table, by which the pyrites and other sulphides are discharged over the head of the platform, whilst the lighter silicious matters escape at the lower end. In order that this may be effected without too great an ad- mixture of quartz with the pyrites on the one hand, or without a considerable quantity of pyrites escaping with the quartz on the other, very nice adjustment is required; but, if carefully attended to, this machine appears capable of affording satisfactory results, and the washed pyrites retains but a small amount of impurity. It is, how- ever, evident that when the pyrites is thus rendered free from any admixture of silicious sand, there is some danger of a loss taking place through the escape of a portion of the sulphides from the other extremity of the table. These tables are, in California, sometimes employed for the direct concentration of tailings flowing from the riffles. The tailings enter by a spout, five inches wide, but which expands at the extremity into a fan-shaped form, so as to be of nearly the same width-as the table itself. This has its end closed by a fillet, in which is a line of numerous small holes, fitted with regulating pegs. The table is formed of a perfectly flat sheet of copper, two feet two inches in width, and about three feet in length, suspended by iron VEIN MINING IN CALIFORNIA AND AUSTRALIA. 195 rods in such a way that its degree of inclination can be readily varied by means of simple regulating gear. In order to render the motion perfectly regular, the table is held in its position by means of spiral . springs, attached near the middle of each side, and connected with a wooden framing. The necessary shaking motion is imparted to the table by rods on either side, moved by eccentrics on a shaft, on which is a small fly wheel, which is driven by a pulley and belt connected with a conical roller, opposite to which is a reversed roller of the same kind, with which it is connected by a belt, by changing the position of which, the speed may be easily regulated. The throw of this table is about two inches, and the speed at which it works very great. When this machine is in operation, the pyrites is discharged over a lip into a small box, whilst the impoverished tailings pass off at the other extremity, and are washed away by a . stream of water. This is a very ingenious apparatus, and may be made to do its work remarkably well; but the rocker is, nevertheless, more frequently employed, and possesses the advantages of being cheaper, doing its work more expeditiously, and not requiring such nice adjustment. In addition to the contrivances which have been described, innu- merable appliances have been invented, and in many cases patented, for the reduction and amalgamation of gold quartz, and the concentra- tion of tailings. An immense amount of ingenuity has been expended on various machines for effecting all these operations at a cheap rate, and some of them bear evidence of great mechanical skill: up to the present time, however, it may be certainly said that most of them have been more extensively advertised than employed. Extraction of Gold from Sulphides—The Hepburn and Peterson, as well as the Wheeler, Varney, and other pans, extensively employed in Nevada for the treatment of silver ores, are sometimes used for this purpose; but as these machines were originally designed for the extraction of silver from its ores, they will be described under the head of silver. | The arrastre, used in the Grass Valley district for the treatment of scrapings taken from the copper plates of the amalgamator, and other residues rich in gold, consists of a basin of cast iron, four feet in diameter, and of which the mullers are also generally of iron, although they are sometimes, but more rarely, made of stone. These are set in motion by a central shaft connected by a belt with the other machinery of the mill, the cleaning up being effected in the usual way, except : 02 196 GOLD. that, as the iron pan is free from joints in which an accumulation of mercury and amalgam could take place, it is more easily managed than the same machine with a stone bottom. | In some establishments, as at Allison Ranch, the tailings are passed through a series of iron basins warmed by steam, and provided with mullers, not unlike, in their construction, those of the ordinary Wheeler pan; but they are less efficient than the pans employed for the treatment of silver ores, and are by no means generally adopted. Bauxz and Guiod’s Amalgamator—This machine, which is repre- sented Fig. 36, is occasionally used for the extraction of gold from tailings. Baux and Gutop’s AMALGAMATOR. In this apparatus the water and ores are introduced at the bottom of the pan, through a hopper bolted on its side, and the discharge of tailings is so arranged as to be from the highest point, which is the centre of the lid, whilst the substances being ground are thrown by centrifugal action upon a bed of mercury lying in a groove around the internal circumference. This apparatus 1s worked continuously, the tailings from the blankets entering at a, and flowing off by the spout B, cast on the cover of the machine. Chlorination Process——Several establishments employing this pro- cess are carried on, on a small scale, in the neighbourhood of Grass Valley ; and when the gold is in a finely-divided state, satisfactory results are obtained. The concentrated tailings are first roasted in reverberatory furnaces of the ordinary construction, generally heated by wood, until no further | VEIN MINING IN CALIFORNIA AND AUSTRALIA. 19% smell of sulphur is evolved, a little charcoal or salt being sometimes added, towards the close of the operation, for the purpose of decomposing any sulphates or arsenical salts-which may have been formed. This roasting is conducted at a very low temperature, and consequently ordi- nary bricks are alone employed in the construction of the furnaces, which are of sufficient capacity to work a charge of from a ton and a half to two tons. After the expiration of from six to eight hours the charge is withdrawn and spread evenly on the floor to cool, after which it is repeatedly sprinkled with water, and turned over in order to get it regularly and suitably moistened throughout, since on the degree of humidity of the mass greatly depends the success of the subsequent operations. When properly moistened, the roasted pyrites is intro- duced into large wooden tubs, about seven feet in diameter, and from twenty-five to thirty inches in depth. These tubs are provided with false bottoms, beneath which chlorine gas is introduced, and allowed to permeate the mass of damp auriferous oxide of iron. At the bottom of each tub are two holes, one for the introduction of chlorine through a lead pipe connected with a leaden gas generator, and the other for running off the solutions. The gas is produced from a mixture of common salt, peroxide of manganese, and sulphuric acid ; and after covering the tub, and keeping up the evolution of gas during from twelve to fifteen hours, the cover is removed and clean water introduced. Water is thus added until it reaches the surface of the charge, when the discharge pipe is opened and the liquid, containing chloride of gold in solution, drawn off into glass carboys. Solution of sulphate of iron is now added, which precipitates the gold in the form of a dark brown powder, readily separated by decantation, and filtra- tion, and subsequently melted into bars, which generally contain about 995 thousandths of gold. This process, when the gold is in a finely-divided state, affords good results; but the larger particles of metal not being dissolved in the time necessary for effecting the solution of the smaller ones, they are often partially attacked only, and unless great caution be exercised, a loss is the result. A sample of the residues from the chlorination vats of one of the establishments at Grass Valley, afforded us, by assay, 18 dwt. of fine gold per ton. The compositions of three samples of pyrites concentrated from tailings, are given in the following analyses by Mr. F. Claudet, who has kindly communicated his results, 198 GOLD. | ANALYSES OF AURIFEROUS CALIFORNIAN PYRITES, CONCENTRATED FROM TAILINGS. | From Froin North Star, | Grass Valley. near Sonora. Grass Valley. Up MUt cree 46°700 37°250 43°720 AYBCLIOA ooe Uee 0°310 8°490 1°360 Fron) 2) 286) oe 41°650 36°540 39°250 Copper . “3? FY. trace trace 0°220 Fea, Ge RGR re 0°400 trace Goldie aca tad 0:037 0°302 0°026 . OUmer I 3.. “lanites te 0°036 not determined 0:012 (abe Hig usc ed . bE 0°150 Biligaus sais pee 10-970.) + Je. 175180 . 14'230 | 99°703 100°162 | 98'968 Per Ton of 20 ewt. | oz. dwt. gr. | oz. dwt. gr. oz. dwt. gr. | Gold. Head 19 a"tG | 98 13 0 810 0 | | Silver!) oY. i 11169" 318-0” | | Amalgamation im Pans.—Instead of stamping auriferous quartz, either with or without mercury, in the battery, and subjecting the sands flowing from the gratings, to the different operations which have been described, they are sometimes, on issuing from under the stampers, at once collected in settling pits, from whence they are removed by manual labour, in order to be afterwards ground in pans, similar to those employed for working silver ores, and which will be described when treating of that subject. However suitable this method may be for operating on small quantities of very rich quartz, it is evi- dently not adapted for working large amounts of moderately auriferous rock, and we are not aware of there being, at the present time, any establishment operating extensively and regularly on this principle. Retorting—The amalgam of gold and mercury collected during the progress of the, various operations connected with the treatment of gold quartz, 1s first filtered, in order to remove the excess of mercury, VEIN MINING IN CALIFORNIA AND AUSTRALIA. 199 and afterwards retorted and melted into bars for the market. In California this expulsion of the redundant mercury is generally effected by well wringing the amalgam in a buckskin, although a piece of closely-woven canvas may, after being wetted, be employed for the same purpose. The amalgam is in this way formed into balls of about the size of large apples, which, after being well squeezed, afford from 35 to 40 per cent. of retorted gold. The retort commonly employed in quartz mills resembles in form and size a large black- lead crucible, furnished with a well-fitting cover, kept in its place either by a screw clamp, or by a clamp and wedge, and into which is screwed an inch iron pipe bent, with a gentle turn, at right angles, and, at a distance of about thirty inches, again so bent downwards as to form another angle. | Before using this retort, it must be slightly covered on the inside, by the use of a rag attached to a stick, with a paste made of water and clay, or sifted wood ashes, to prevent the adhesion of gold in case of too much heat being accidentally applied. The lumps of amalgam are now introduced, and the face of the lid carefully luted with a mixture of clay and wood ashes, after which it is placed on the retort, and securely fastened in its place by means of the clamp. The crucible and its charge are now introduced into the furnace employed for melting retorted gold into bars, and which for this purpose may be fourteen inches square, and 1 ft. 8 in. deep above the fire bars. The end of the pipe will now be a short distance only from the floor of the furnace room, and beneath it is placed a vessel of water into which a piece of canvas, which is bound round it so as to form a short hose, is allowed to dip; the level of the liquid being constantly maintained by the flowing off of the water in the receiver, in proportion as the condensed mercury accumulates. The conden- sation of quicksilver is often effected by means of wet cloths bound around the descending limb of the pipe, and which are constantly kept cool by the application of water: the same result is sometimes more neatly and readily produced by the application of a Liebig’s condenser. : When it has been thus arranged in the furnace, the: fire may be lighted and gradually increased, until the retort has acquired a dull red heat, care being at the same time taken to effect the perfect con- densation of the mercury by a constant supply of fresh water to the eduction pipe. The heat is thus kept up for several hours, according to the size of the retort and the amount of amalgam operated on ; but the 200 GOLD. production of a decided light red heat, visible in daylight, should be avoided, since at that temperature the gold might not only be partially melted, but the retort itself seriously injured. When the pipe begins to get cool, and no more drops of quicksilver are observed to fall from its extremity, the operation is completed, and the fire may be with- drawn; but the cover should not be immediately removed, since a hot retort, even after the operation has been slowly and carefully con- ducted, gives off mercurial vapours, which would be, if inhaled, highly injurious. The water covering the mercury in the receiver, should, during a properly conducted retorting, remain perfectly clear and free from turbidity, since if it becomes milky it may be regarded as a proof that the heat employed has been too great. A forced retorting saves little or no time, and the mercury under such circumstances . is imperfectly expelled, whilst the retort itself is rapidly destroyed, and soon rendered unserviceable. In order to obtain satisfactory results, the retort should be heated gradually, kept a long time at a black red heat, and allowed to cool before being opened. The fuél employed in the furnace is either coke or charcoal, and as soon as it has sufficiently cooled, the retort may be opened, and the spongy gold, which is of a light yellow colour, may be removed for the purpose of being melted into bars. When very large quantities of amalgam have to be dealt with, a fixed retort not unlike those employed in the manufacture of coal gas may be made use of, and, particularly when - employed for the retorting of silver amalgam, is frequently made of a large size. Melting Retorted Gold—The fusion of retorted gold is commonly effected in the furnace employed for the distillation of amalgam in the small crucible-shaped retort. The melting is performed in black-lead crucibles, and the fuel employed, coke or charcoal. The crucible should be annealed by being gradually warmed, before being subjected to the full heat of the furnace, and a small quantity of borax is placed in it with the retorted gold. The gold from the retort being porous, occupies a considerable space, but after melting takes up much less room; so that as soon as the first charge has become fused, the cover may be removed and a further addition of retorted gold made. When the gold has become thoroughly fused, the crucible is withdrawn by the aid of a pair of strong tongs, furnished with jaws for enclosing and supporting its sides, and the metal is poured into moulds of cast iron, In order to render the handling of the pot perfectly safe, and to prevent any chance of the slipping of the tongs, its handles VEIN MINING IN CALIFORNIA AND AUSTRALIA. 201 should be provided with a movable link, which, by keeping them tightly together, prevents the jaws from relaxing their hold on the crucible. ; TABULAR STATEMENT, Or THE OPERATIONS OF THE PRINCIPAL QUARTZ MILLS RUNNING IN CALIFORNIA IN THE YEAR 1861.—-By W. ASHBURNER.* Ne Oe (es = 3 3 ae eo Pf te A) S. (68) a lEe.i\$8/ 88 (FS) Fa |28l ying | aa] ee Name and Locality | Water, or s 6 q ea a a5 = ~ > aoe 3 a. =P) és bey $8 ne D - of Mill. Beam. | 2S (SH se iesosis 5) 8S SSel seve Bl ton les! oo S| ‘om |nl [A Sele Ss) 4, (35 a, ay | a ae eae AS NSS! So ees pe SSO er eS 8 jae ‘ > a2e(° ide |o Smls ) oe. S 84 A S o | S 4 °8 o aie , ie = 7 Os . ot 25 2a Eee — ieee | a | ee es ee a Mariposa County. me e He) LODE: | Rods, SBentonm- . ..- »| Water |64) 550 60 |12| 1:00 | 5 | 80 -- |0°0027/$3°53, $8°98 |$°559) $1-04 Bear Valley. . .| steam | 8) 1000 65 |12| 1°97] ... | 20 0°158 |0°007 | 6:00) 25°24 |1°618} 3-10 Mount Ophir . .| steam |24; 500 5G IcLO VSOrr 26 | 0176 |0°019 | 6:00) 16°94 |1°909] 9:96 Princeton . . .| steam |12) 600 60 |14| 1:27] 5 | 23 07118 |0°026 | 5°43) 27°42 |1°423) 3-18 TUOLUMNE CouNTY. Unione... «| water |20 500 60 | 13) 0°98 | ... | 20 ee |0°031 |13 00) 50°00 |3°145| 3-81 Bigatti -2. + - =| “steam 10 500 OS) PelS OOD es 8% | 0°130 |0°030 | 5°00) 25°36 |2°820) 9-83 Lomberdo’s. . .| water 8 650 58°14) 1°83') ... | 15 «» {0°016 | 8:00} 20°00 |1°243) 1-64 Hnveke. s.. «| water’ |20 600 65) 11 | 1°08 | ... | 40 Sc5 aoe, Pearoal L200) ces 1:03 Confidence . . .j| steam {10 480 54°} 12|-0°78 | 9 | 10 0°175 |} «.. |-1°60) 10°00 |2:204| 9-29 Telegraph . . .| water {10 475 G2uh cen sea O 8 ae sean eo OO) S000 Hes. 2-00 Knox and Co... .| water | 5 te eSeuiitisetn || recs hale we: cor seo |, 6°00) 20°00: |. 1°25 Yaney (Dry). . .| water | 6) 9800 Soo | eeset Pe ees soe | ar ay mfr aaa — Pe CAlLAVERAS COUNTY. | Crystal(Dry) . .| steam /12) 600 60 | 10] 0-91] 6 8 0°500 |0°128 | 1°50) 80°00 |3:916) 98:31 Angels Q. M. Co. .| steam [16 490 50 it -e. | 0:62 | 10. | 24 0°130 |0°125 | 2:00) 5°00 |1°827| 9:03 Blue Wing (Dry) .| steam |24 ay Hot Gera ase ae 8 a: one ie Ace AMADOR COUNTY. Oneida . .. .| steam (16 aes 52 | 10 wes et LO 0°250 |0°089 | ... | 10°50 |2°351) 9-84 Eureka cen 40} 590 | 80|10| 1:19 |’ 6 | 60 | 0-066 |0-064 | 2°50) 10-25 |0-963] 1-32 Badger (Upper) .| water /|16 400 80) LO ORE coe 29 « |0°055 | 2°50) 10°25 |0°646] 0-67 mier(uower) .| water 12 400 SOLON OSL. Pesan p20 «- |0°057 | 2°50) 10°25 0-759] 0-78 Herbertville (Dry). | steam (30 500 65 |} 12] 0°98 | ... | 14 0°371 |0°114 | 4°50} 20°00 |3:043| 4-59 American Q.M.Co.| steam /20| 575 70 |10| 1:01] ... | 25 | 0°160 |0°067 | 2°93) 10-00 |1-476] 1-79 Spring Hill. . .| steam [31/400 & 600} 70 | 10 sos rk OO 0144 |0°050 | 2:00) 10°00 |1:394| 1-63 EL Doravbo County. Empire (Logtown). | steam (10 600 CO ASH 1LetS |) 6 12 0°145 |0°054 | 2°75) 10°00 |0°990! 1-49 Union(AurumCity)| steam (10 450 TOM ecw ly hoee a 20 0°175 aoe eee | 30°00 |2°046| 2°05 Tulles(GrizzlyFlat)| water |11/1000°500| 42|...| ... ceenimecs ay. tas 500) 10°00: b> 2. ae PuLuMAsS County. Hurekaes 25. os . water |28 ie Psy ese i eee Sail seas oy Zac HON aie Lo Aeie Waeaen 6:27 Mammoth .. .| water {12! 800 40} 8| 0°65 | ...-} 10 conn HOCO2 20s sen PaO COC) sep : SIERRA CounrTy. Sierra Buttes . .| water |24 600 50 | 10) 0-76 | 9 | 30 . |0°027 | 5°87] 14°82 10-633] 1°36 Independence . .| water 12 550 48 | 9| 060] 8 | 10 «- |0°033 | 5°00, 15°00 |0°858] 2-90 NEVADA CouUNTY. Nevada Q. M. Co..| water |12 850 COPA ba eS: Ls «- |0°198 | 4:00) 17°14 |1°466| 2-65 Gold Hill. . . .| steam [21 730 52 | 14} 1.34 |} 14] 35 0171 |0°044 | ... leustom|1°600| 2°30 Massachusetts Hill} steam |16|) 1000 55 |12| 1:67 | 4 | 33 0°183 |0°024 |26:00] 70°00 | ... 2°91 Empire No.1 . .| steam ae Hey leeselekses 0°104 |1°120 |. ... BcOOue ees 1°37 eNO, . 9. |. Steam 6 900 62 |14/ 1:97 | 5 | 18 0°141 |0°109 |10-00| 28-00° » 1°66 Orleans wie ea Steam |) 9 606 32 {10} 0-48 | 24] 8 0°241 |0°046 | 3°00 ai 3°23 Allison Ranch . .| steam | 8} 950 DOW PLoate ee (ik Oe tele 0°176 |0°023 |20-00) 50°00 |1°678) 3-60 Lady Franklin -| steam | 8 950 CON L402 rar 22 OL30 0:01 1°279| - 2°05 Forest Springs. .| water (10! 800 60 | we | oes 4 8°76}... |0°044 |15°00| 52°35 |1°343] 2-98 | * Geological Survey of California, vol. i. p. 475, 202 The present average cost of treating gold quartz 5 estimated by Mr. Ashburner as follows :— — 7 any - In Water Mills, water free . purchased , In Beas Mills : ‘ \ i ‘ , . ‘ Ac 4 ‘ - . a4 bis “ae ¢ <4 P . \ \S . ~— 5 ese ~ Pes tr > ie A ra 6 Ps al . . 9 e } , . CHAPTER X. VEIN MINING IN HUNGARY AND BRAZIL—SODIUM AMALGAM. AURIFEROUS VEINS AT SCHEMNITZ— STAMPING MILLS—HUNGARIAN BOWLS— SHAKING TABLES—CONCENTRATION OF AURIFEROUS SLIMES — GOLDLUTTE SCHEIDETROG—RESULTS OBTAINED—MODE OF OCCURRENCE OF GOLD AT MORRO VELHO—STAMPING—STRAKES—TREATMENT OF FIRST TAILINGS— TREATMENT OF SECOND TAILINGS—AMALGAMATION OF CONCENTRATED ORES— LOSS OF GOLD AND MERCURY—COST OF WORKING—APPLICATION OF SODIUM AMALGAM—NOT GENERALLY EMPLOYED IN CALIFORNIA-—ADVANTAGES STATED TO RESULT FROM ITS USE. Huncary.—The metalliferous deposits of Schemnitz, in Lower Hun- gary, are generally regarded as being true veins, although they do not always exhibit distinct walls separating them from the enclosing rock, which is, however, in the neighbourhood of the veins, usually more or less decomposed, and often contains a considerable amount of iron pyrites. Some of these lodes are sixty feet in width, and have been worked to a depth exceeding two hundred and fifty fathoms. The veinstone is principally quartz, through which are disseminated, in a finely-divided state, galena, iron pyrites, gold, and sulphide of silver. Stamping Mill—These ores are treated in stamping mills, con- structed according to the usual continental system.* Each stem or lifter consists of a wooden beam, usually made of oak or beech, twelve feet in length and six inches square, the lower ex- tremity of which is provided with a head of hard white cast iron. These are cast with a shank, which is inserted into the wood, and securely held in its place by two strong iron bands, driven on over the lifter and tightly wedged. The stamper thus prepared weighs two hundred and fifty pounds, although in some cases they do not exceed * Our data relative to the treatment in Hungary of gold ores by amalgamation, have been chiefly derived from a paper published in 1846, by M. Pache ; and as we are without any precise information relative to the modifications which may have been since introduced, the descriptions of the various processes must be considered as applying to that date. The title of the paper referred to is as follows :—“ Sur la Préparation mécanique des Minerais dans le district-de Schemnitz (Basse Hongrie), par M. H. Pache.”—Ann. des Mines, Tome x. série 4. 204 . COED; one hundred and twenty pounds in weight. The axle is of wood, nineteen inches in diameter, and provided with iron journals, the stampers being lifted by means of wooden cams and tappets. Each pestle has a lift varying from eight inches to a foot, and strikes, on an” average, seventy blows per minute. The battery box is composed of thick planks, firmly put together; and the bottom on which the stampers fall is prepared by tightly beating in, with a heavy iron ram, fragments of hard quartz, which are introduced in successive layers. These mills are generally so constructed as to be self-feeding, although in some cases they receive their supply of ore from a small inclined hopper, into which the stuff to be stamped is thrown by manual labour. They have no gratings, and discharge the pulverised ore over the edge of an.aperture running the whole length of the battery box, the height of which, from the face of the stampers, can be regulated by means of a sliding apron. The stamping is conducted wet, about three cubic feet of water per minute being supplied to each battery of five stampers. The apparatus employed for the extraction of gold at Schemnitz is represented, Plate V. fig. 1, being an elevation, and fig. 2, a plan of the arrangement; B is the last battery of a range of stamping mills; A the axle, 6 the table before flosh holes, ¢ the canal through which the stamped ore escapes from the battery box; d, e, 7, are three canals or spouts at different levels, for the passage of slimes. Hungarian Bowls, &e.—The eight amalgamating mills, 1, 2, 2, 4, and 1’, 2’, 3’, 4’, are disposed in two rows, of which the first is placed four inches above the other. The divisions g are seven inclined planes having the same flooring, but separated from each other by partitions two inches wide, and an inch and a half deep. The distance between these divisions is eighteen inches, and the length of the table six feet ten inches, with an inclination of fifteen inches between its two ends. Each of these inclined planes is completely covered over by two pieces of canvas a little wider than the platform, and slightly exceed- ing half its length. : The mills are composed of a cast iron basin, a, Plate V. fig. 3, half an inch thick in the metal, twenty-two inches in diameter at top, and seventeen and a half inches at bottom, with an internal depth of seven inches. This basin is simply placed, without any special foundation, on the floor, to which it is secured by means of two iron ears. The wooden cylinder 0 is bolted vertically in the centre of the pan, and is bound at top and bottom by iron rings, whilst at its upper extremity VEIN MINING IN HUNGARY. 205 is an iron thimble, for the reception of the lower end of a vertical shaft. The runner, figs. 4, 5, 6, destined to revolve in this basin, is of wood, the pivot ¢ of the spindle being so placed as to be exactly vertical, both with regard to the bottom of the basin and the face of the wooden block forming the revolving portion of the mill. This adjustment is readily managed by means of the tripod e, f, g, at- tached to the wood at its extremities, and of which the central boss h fits on to the square part of the spindle. The circumference of the wooden block a’ is bound by two strong iron hoops, its lower face being provided with twelve blades or stirrers of thick sheet iron, driven into the wood, and projecting about half an inch, arranged as the radii of a circle. The space between the runner a and the pan a receives 28 lbs. of mercury, the distance between the two surfaces being regulated by means of the nuts, 7,7’. Formerly this was so arranged that the blades penetrated slightly beneath the surface of the quicksilver, but it has been ascertained that the amalgamation pro- gresses more rapidly, and with less loss of mercury, when the lower edges of the iron stirrers are kept slightly above its level. The dis- tance allowed between the circumference of the runner and the inside of the pan within which it revolves, is about one-sixth of an inch, and the upper extremity of each vertical shaft.is retained by two bearings, Kk’, fig.1, These shafts have also a coupling in some portion of their length, which enables one or more of the runners to be. thrown out of action, without interfering with the remainder. Motion is communicated to the various mills by means of two mitre wheels, one of which is attached to the axle, whilst the other is keyed on a shaft on which is a pulley, /, around which is an endless strap bearing on the riggers of all the mill runners, as shown by the dotted lines. The relative diameters of the mitre wheels are so cal- culated as to cause the runners to make eighteen revolutions per minute. Higher and lower.speeds have occasionally been given to these mills, but the above number of revolutions per minute has been found to afford the most satisfactory results. It has also been ascertained that from eight to nine mills are required for the treatment of the sands and slimes resulting from the action of every ten stampers, which amounts to about seven thousand pounds in the course of twenty-four hours. The working of this apparatus pro- ceeds concurrently with that of the stamping mills, and requires but little supervision. The slimes are discharged into the canal or launder, c, from which they pass through a screen of wire gauze, m, 206 GOLD. by which any impurities, such as fragments of wood, are separated ; and then flow into the canal d, from which they pass through four small spouts into the basin-shaped cavities in the runners of the mills 1, 2,3, and 4. The slimes now descend go as to come in contact with the mercury contained in the basins, a, where they are constantly agitated by the iron blades fixed in the revolving wooden blocks, and finally rising through the annular cavity, between the edge of the runner and the inside of the basin, escape by the lip 2 into the mill immediately below it. Here precisely the same action takes place as in the first ; and the slimes flowing off into the canal e, are distributed over the inclined tables, g, by means of apertures prepared for that purpose in the side of the launder. Once every month the mills are thrown out of action, and the whole of the mercury removed. The quicksilver is now subjected to two successive filtrations, and an amalgam is obtained, which usually contains from twenty-eight to thirty-three per cent. of gold, and which is treated by distillation. The mercury separated by filtration, and which still retains a little gold, is returned to the pans, and the apparatus again put into operation. The monthly loss of mercury in an arrangement of eight mills, is usually from two anda half to three ounces. | One boy readily manages the supervision of from ten to a dozen of the tables, y, and every two hours removes the cloths from each in succession, and, after having washed them in a tank prepared for the purpose, replaces them as before. In the case of ordinary ores, affording from fourteen to fifteen loths per thousand quintals (about three dwt. per ton), eight loths are extracted by the mills, and from five to six by the inclined tables, so that from one to two loths only are obtained from the slimes by smelting. The sands and slimes passing off from the tables are collected in settling pits and labyrinths, from whence they are subsequently removed for concentration, prin- cipally on shaking tables. : Shaking Tables—The shaking table employed at Schemnitz, which is somewhat peculiar in its construction, is represented Plate V. figs. 7, 8,9, and 10; the first being an end, and the second a side elevation. The part a of the table is called its head, 6 is the tail, and ¢ (figs. 9 and 10) is known as the tongue. Of the four chains by which the table is suspended, the two at the tail are the longest, and are attached to the wooden rollers d, furnished at each end with ratchet wheels by means of which their length may be easily VEIN MINING IN HUNGARY. 207 reoulated.. The wooden axle e is furnished with either two or three cams, which successively throw forward the lever /, articulated at g, carrying with it the rod hk, which pushes the table in the same direc- tion, as long as the cam continues to act on it, but, as soon as it is released, allows it to fall back with a sudden jerk into its original position, the tongue ¢ at the same time striking against a stout bar placed before two of the pillars of the framework for that purpose. The elasticity of this bar causes a series of vibrations in the table, which gradually become less, until it is again forced forward and thrown by the cam as before described. The position of the elastic bar forming the stop is easily regulated by wedges, whilst the length of the rod # admits of being adjusted by the use of the screw 2, and wheel and pinion £X’, in such a way as to increase or diminish the throw of the apparatus. Above the axle of each table is a wooden platform, on which are stored the slimes to be treated, and which are from thence transferred to the cistern /, of which the bottom has a considerable inclination. Below the semicircular opening m, in this box, is a small spout or gutter n, leading to the higher end of the inclined plane o. This head-board is composed of two distinct planes, placed one above the other, but both inclined at the same angle, and on the upper one are arranged a number of little wooden buttons, o’, by the arrangement of which the regularity of the flow of slime over the whole surface is readily secured. In some cases, a strainer of wire gauze is placed across the head of the lower portion of the table head, for the purpose of collecting chips or any other impurities that may have accidentally become mixed with the slimes. The two launders, g and g, run the whole length of the establishment, the first being used for the purpose of supplying clean water, and the second for carrying off the impoverished slimes. These tables are set in motion by water-wheels, one horse power being sufficient to keep in operation ten tables, each of which is capable of washing the slimes produced by four stampers. The working of these tables is conducted as follows:—Slime is thrown with a shovel into the cistern 7, and a small stream of water allowed to fall into it, which, mingling with the slimes, escapes by: the aperture m, and descending in an even flow over the inclined plane 0, covers the whole width of the head of the table. In order to facilitate the mixture of the slimes and water, it is generally necessary to use a shovel, by which the contents of the box are occa- sionally stirred ; and when the sands mixed with the slimes are some- 208 | 7 GOLD. what coarse, a small wooden hoe is employed to rake the deposit, on the head of the table, gently against the current. The tension of the table, or the sine of the angle formed by the suspension chains with the perpendicular, from the point at which they are attached, is made to» vary in accordance with the nature of the slimes to be treated, although those of the lower end 8, generally remain the same for all descriptions of slimes. The tension of these chains is generally about five and a half inches, but for the chains of the .head a, it is not more than two inches for coarse slimes, whilst for very fine slimes it may be as much as eight inches. The extent of the throw of the table is also made to vary in accordance with the nature of the stuff to be wrought. For coarse slimes it may be as much as five and a half inches, whilst for very fine ones ’ it is sometimes reduced to two inches. The number of oscillations of the table is so managed that it shall be constantly in motion, with- out any period of repose, the number of throws per minute, for coarse slimes, being about sixteen, and for very fine ones, from thirty-five to forty; but it must be remembered that in each case the elasticity of the bar against which the tongue is made to fall, produces from ten to fifteen secondary oscillations, gradually becoming less decided, until the table is again thrown forward by the cam. . After the apparatus has been in action a certain period, varying according to the nature of the slimes worked, from a few hours to two, or even three days, the deposit of enriched matter, towards the head of the table, accumulates to a depth of some six or seven inches, so that the operation could no longer be continued without danger of its flowing over the sides. The apparatus is then stopped for the purpose of being cleaned up; and as the deposit varies in richness in different parts of the table, it is divided into three distinct portions, each of which is differently disposed of. Even that at the head is, however, rarely sufficiently rich to be sent directly to the smelting works, and is generally again worked over. The deposit in the middle, which is divided into two classes, is invariably re-treated, whilst that at the lower end is usually rejected as useless. The different products — thus.obtained from the first table are further enriched by being subse- quently re-treated on separate tables. At Schemnitz, in addition to shaking tables, sleeping tables are some- times employed for the concentration of the finer slimes, but these are of the usual construction, and are rather used for the purpose of washing lead slimes, than for those of which gold forms an important constituent, > VEIN MINING IN HUNGARY. 209 Having described the amalgamating mills and shaking tables, it remains for us to follow the treatment of the rich auriferous materials collected on the cloths spread on the inclined tables, and subsequently accumulated in the tanks into which they are washed. The final washing of these rich deposits is a delicate operation, performed first in the gold box (goldliitte), and afterwards in a kind of scoop- shaped batea, called a scheidetrog. Goldititte—This apparatus is represented, in plan and elevation, Plate V., figs. 11 and 12. It consists of an inclined trough, twelve feet in length, and twenty inches in width, with an inclination of about three feet on its entire length. Its end and vertical sides are nailed to the bottom, and are ten inches in depth. The upper portion of the plank forming the bottom of this arrangement has, cut in its surface, numerous small riffles, which form zigzags, running at an angle of 45° with the upright sides. Ata distance of seven inches from the upper end of this box, is a dam a, rather shallower than the sides, behind which a stream of water is introduced by means of a tap, and which, flowing evenly over its upper edge, distributes itself regularly on the auriferous slimes placed at 6. The bottom of this arrangement must be so fixed on the woodwork which supports it, that its transverse section is at all points perfectly level. The workman stands on the plank, ¢, and the three rectangular reser- voirs, d, ¢, f, are for the purpose of receiving the products of the operation. The working of this arrangement is conducted very much like that of an ordinary sleeping table. The ore is added in small quantities with a shovel, water is allowed to play over its surface so as to distri- bute it in the box, and then clean water alone is made to flow over it : whilst, at the same time, its surface is gently swept upwards, in a contrary direction to the current, with a brush or small heath broom. The products obtained are :— Ist. A coarse argentiferous slime containing gold, galena, and iron pyrites. : 2nd. A fine slime containing the same substances. ord. A concentrated slime, rich in gold. a The two first products are usually re-washed in the same apparatus before being sent to the smelting works, The third, on the contrary, contains nearly the whole of the gold, and is at once washed in the scoop-shaped batea. P 210 GOLD. Scheidetrog.—This instrument is represented, in plan and elevation, Plate V., figs. 18 and 14. It is neatly cut out of a single block of wood, elm or sycamore being generally employed for the~ purpose. The workman holds this below the lower end of the washing box, and when in that position, the auriferous slimes are carefully brushed into it by the aid of a broom, assisted by a gentle current of water. He now holds it in both hands, placing his thumbs in the semicircular depressions a a’, and stationing himself before a tank of water, he begins giving to the instrument a motion similar to that of the shaking table, striking at each oscillation the end 0 against his thighs. After work- ing in this way during a few minutes, the greater portion of the sulphides are washed off, and, in order to eliminate the remainder, he holds the batea in a slightly inclined position with the left hand, whilst with the right he directs on it a small stream of water from a horn in which a minute hole has been bored. This operation is com- menced at the upper end of the instrument and gradually continued downward, by which means the gold, gradually freed from impurities, begins to make its appearance in the form of a pale yellow crescent- shaped streak. The product of each operation thus conducted is washed into a receiver, the contents of which are again re-washed, in the same way, at the close of the day’s work. The final product thus obtained is amalgamated, by agitation with mercury, and after filtra- tion in the usual way, retorted, and melted into bars. The relative values of the products obtained at Schemnitz from ores operated on in this way, after deducting the cost of metallurgical treatment, were, in 1846, nearly as follows :— Per cent. CONG ee So tes nae Stade agen eee mea le Silver ree Wits Mee caer ce eee Res Monte Ahr pee) send. ys tee oe i ee Obie... Sa: oe Brazit.—The rock treated at the Morro Velho mines is principally a mjxture of magnetic, arsenical, and common iron pyrites, finely disseminated in, and intimately mixed with, a quartzose gangue. The composition of what is called pure ore may be taken at about forty- three per cent. of silica, and fifty-seven per cent. of pyritous matter. Of these minerals, arsenical pyrites is usually the most auriferous, although it does not occur in large quantities. Pure specimens of fel ce la hah nscae PrN EON ee ese og ete yaa’ WISCHEWNIT?. LOWES " a a sll Wile Biot a DE ari : ~ a la AE on ae inia.. Ws naaanalh pre ere Se weal ea a YY, Yy cant é Jasna a soe ee Scale of Fig’ J a oF COLD AT SCH LOWER HUNGARY. EMNITZ, MACHINERY EMPLOYED For THE EXTRACTION REP E RB GCE Be, Figs) and 2%. Cushing and Amalgamating Apparatus A. Cam-axle of Stamps B. (Coffer of stamps b. lable before Flash holes” od.et Spouts at difkrent levels tor the passage of slimes 12.34 and 12:34 Amalyamating bowis 9: _ frelined planes or strakes ICA Bearings of Mill shatie — Pulley m Sheet of wire gauxe Fig 34.5 and 6 Details of Bowls a Cast Iron basin. — a’ Wooden. runner 6. Glinder w Centre of pan. — c. Spindle ef g. Iriped fitting on vertical shati hu. tt Regulaung nuts Figk78,I and 10 Concentrating Apparatus. a.b, Shalung table. — c Tongue d. Vboden’ roller towhich table is suspended © lam-axte. — ¢ Lever guing motion to table 4, Bearing of Lever arm Rod which pushes table backward t. wating screw. k ald i Wheel and puuo0n Ll. Same cesterr — m Opening wito quitter rn. 0 Inclined plank Regulating butions. — pg Launders kig> Wand 712 (reldlitte C._ Stage for Workman. det Recer tanks Fig’ 13 and 14. Scheidetreg. a.a. Handles. — bh. Rim at back G8 5E8Saq,, Oo "e555 i &FEN.S pon 48.Charing Cross,Lon VEIN MINING IN BRAZIL. 211 this substance afford, by assay, from four to six ounces of gold per ton, and wherever crystals of this mineral make their appearance the yield of the precious metal is large. Cubical pyrites is of more frequent occurrence, but is far less rich in gold ; solid specimens of this substance, but slightly mixed with quartz, yield about an ounce and a half of gold per ton by assay. Magnetic pyrites constitutes the largest proportion of the sulphides found, but this is very slightly auriferous, since pure specimens generally yield rather less than four dwt. per ton. Branches of clay slate are often found in the principal veins, and this rock, under such circumstances, commonly affords, by assay, from five to seven and a half dwt. of gold per ton. Quartz without.any admixture of sulphides has never been found to be auriferous, and it is a remarkable fact that the smallest speck of gold is rarely seen, previous to concentration, in any of the ores from this mine.* Spalling.—The ores on being drawn from underground are delivered on the spalling floors, where they are broken into fragments of a proper size for the stamping mills; and the clay slate, and other com- paratively sterile rock, are picked out and thrown into separate heaps. Iron hammers were, until 1857, employed for breaking the ore on the spalling floors, but in that year cast steel was substituted for iron, the result of which has been a saving of at least fifty per cent. on the annual cost of these tools. Stamping.—The stamping mills employed at Morro Velho are worked by water, and are of the ordinary Cornish form of construction, except that each lifter is provided with four iron guides for keeping it in its proper position. A new stamp head weighs 230 Ibs., and when entirely worn out is reduced to 59lbs. The average weight of a stamp head may thus be taken at about 150 lbs., and the period of its duration at four months. The total weight of a new pestle, 7. ¢. head, lifter, tongue, and all the other work attached, is about 640 lbs. ‘The lift of the stamper is from ten to twelve inches, the number of blows struck per minute varying from 60 to 80, in accordance with the greater or less supply of water for the wheels. The battery box, or coffer, differs slightly in dimensions in the different mills, but is composed of wood lined with sheet iron. The heads are generally worked about three inches from each other, * We state this on the authority of Mr, Hockin, the Managing Director of the Company. Pp 2 212 ~ GOLD. and the same distance from the sides of the coffer. The height from the bottom of the coffer to the grate openings is a matter of great importance, and one that requires much attention, since on this greatly depends the degree of fineness to which the ore will be crushed, as well as the amount passed through the apparatus in the course of twenty-four hours. The stamping mills in this establishment are self-supplying, a blow being given to the feeding hopper, by a peg driven in the central lifter of each set, whenever the absence of ore in the coffer admits of its falling sufficiently low to come in contact with it. It therefore follows, as the stamps do not work on iron blocks, but form their own beds of tightly-compressed ore, that as the heads wear, the bottom of the coffer will grow higher, and the space between the grated open- ings and the faces of the heads become proportionately less. In order to keep a series of stamping mills in a regular and efficient state of working, considerable attention is required to be bestowed on their adjustment; and when the bottom of the coffer has become too high, the working of the heads is so arranged, that before feeding themselves with fresh ore, they shall so far wear down the stamp bed as to reduce it to its proper level beneath the grate opening. This adjustment is readily effected by taking out the pin from the middle lifter, and shifting it higher or lower, as the case may require. It is probable that this operation may have given rise to the term apphed to the regulation of stamps, which is called “ pitching.” The grates employed at the St. John d’El Rey mines are nineteen inches in length, nine inches in width, and made of sheets of copper one-eighth of an inch in thickness. These are pierced with conical holes one-twelfth of an inch in diameter on the outside, tapering off on the other to one-forty-eighth of an inch, where a projecting burr is raised, which is placed toward the inside of the coffer. Copper plates have been found, on the whole, more durable than iron ; besides which they possess the advantage, that when worn out they are readily con- verted into gun-metal by the addition of a little tin, and can then be employed for axle bearings and other purposes. Results obtained.—The rock stamped at Morro Velho is reduced to the state of a mixture of fine sand and impalpable slime, the relative proportions of which will be seen from the following tabular state- ment of experiments :— VEIN MINING IN BRAZIL. pA ks TABLE I.* , From From Size of Mesh. ) Mixture from | Herring’s Lyon’s : Stamps. Stamps. | Of 1,000 grains sifted, on sieve of 10,000 per cent. per cent. per cent. | holes per square inch— Spe a 88°25 95°25 | 93:22 eeor pasa through. . . . ... . 11°75 4°75 6°78 100°00 100°00 100°00 Did not pass through 2,500 holes to MERE ee ge 0°50 0°25 0°33 This auriferous material issuing from the stamping mills is associated with gold in three different states, viz— 1st. Free gold capable of concentration by washing. 2nd. Ditto in a lamellar form lable to be carried off in suspension by water. 3rd. Mechanically combined gold, enclosed in particles of pyrites, but capable of being liberated by further grinding. _ The following table, from the notes of Mr. Dietzsch, affords much practical information relative to the stamping mills now in operation at this establishment :— TABLE II. g : g Se F : Dimension of deems gaan of Ore stamped. Name of MES emin S Stamps. ee eee lial Th. js wie oe lee Tons Ibs peck Blog } lia- ; T ; iz =¥ = 4 °| length. | width. | depth. chee et width. Serie abe co cae iy in. fi. in. | ft. in. | ft in. | ft. in, | fi in. ieee, | OOlOD110),..4 2 2/1 312 0|40 6| 3 8] 36°73] 1°22 2,733 Cotesworth. | 12;61)/11;4;2 2)1 1/1 6131 0|3 O/] 1692] 1:41 3,158 Susannah . 9/65/12) 6) 2 3)1 312. 0/19 2/4 4 | 10°94] 1:21: | 2710 Pere. | 24/78/12)... 2 611 612 0142 6| 6 0 | 34:56) 1°44 3,225 Seeeaere ) 3G 67/12) 41,2 211 3 | 1°10 151 0} & Oo} 6610]: 1°83 4,100 Addison . | 24/73/12} 4/2 2/1 3/110/42 0/6 O0| 35:54] 1°48 3,315 135 * From MS. notes of Mr. F. Dietzsch, Superintendent of Reduction Works. 214 GOLD. Strakes.—The slimes and water issuing from the gratings in front of the coffers, to which a certain amount of clean water is added, are conducted over inclined platforms about eighteen inches in width, and from twenty-seven to thirty-five feet in length, which have a fall of one inch per foot. The first sixteen feet of these strakes are covered with bullock skins two feet two inches long, and of the width of the strake, tanned with the hair on them; a series of baize cloths, each two feet ten inches long, are employed below these, which are again followed, at the lower end of the arrangement, by another series of overlapping skins. A certain quantity of finely-divided gold is caught even on the last of these skins, whilst a considerable propor- tion, estimated at ten per cent. of the total amount present, is carried off in suspension by the water. The skins and strips of baize are removed and washed at regular intervals during the day and night, the time allowed to intervene be- tween each washing up, depending on the nature and richness of the ores treated. In each of the houses erected over the strakes, are boxes or tanks, in which the skins and pieces of baize are carefully beaten and washed, and of which those destined for the reception of the most concentrated slimes are divided by partitions into three separate divi- sions. Into one of them the first three skins from the upper end of the strakes are washed, and into the second is removed the ore collected on skins 4 and 5 of the series, whilst the third division contains water in which the final washing of skins 1, 2, 3, 4, and 5, is effected, after having previously removed the coarser particles in one of the other divisions. The skins and cloths below No. 5 are washed in the same way, but into separate tanks, from which they are subsequently removed and washed over another series of skins and cloths, in order to effect their further concentration, The deposit on the first three skins, known as head sand, amounts to about 0°42 of a cubic foot per ton of ore stamped, and contains from twenty-seven to thirty ounces of gold per ton, all of which, with the exception of about one ounce, is in a free state. This sand is sent without further preparation to the amalga- mating house. The middle sand consists of the deposit collected on the skins Nos. 4 and 5, and contains about six ounces of gold per ton, of which some sixteen dwt. only are mechanically combined with particles of pyrites, This sand is further enriched by being washed over another system of strakes, VEIN MINING IN BRAZIL. 215 The deposit taken from the third compartment of the tank in which | the upper.five skins are finally washed, is called swim sand, and being exceedingly fine, could not be safely subjected to concentration, and is consequently sent, with the head sand, directly to the amal- gamating house. All the products caught below the fifth skin are known as fad sands, and are like the middle sand, concentrated by being washed over a second system of strakes. The apparatus employed for this purpose consists of three strakes, each covered with four skins and seven cloths. At the Herring, Lyon, Powles, and Addison stamps, the skins and cloths are changed every hour, whilst at the others this is only done every two hours. Previous to 1854 the strakes above described con- stituted the only arrangement for the collection of the auriferous materials issuing from the batteries, but in that year some extra strakes were added, as it had been long known that a considerable amount of the precious metal passed off in the slimes. These extra strakes are so fixed as to receive the slimes from the lower end of the original ones, after being first diluted by the addition of some clean water, and the sands collected are subjected to amalgamation without further concentration. The saying of gold effected by these additional strakes amounts to about 38 ounces per month. The valuable nature of the products resulting from the above pro- cesses of concentration, renders it necessary that all parts of the esta- blishment in which they are collected should be protected from theft, and for this purpose the strake heads are securely railed off, and the tanks in which the head sands are washed provided with locked covers. In Californian mills, where the amount of blanket surface employed is proportionately much less than at Morro Velho, that part of the establishment which contains the various contrivances for the separa- tion of gold from the crushed rock, is securely enclosed in a wooden building, under the immediate control of the chief amalgamator. No part of the gold-saving apparatus is, as a rule, kept under lock, with the exception of the tanks, when full, in which the blankets are washed, and the rollers with the mercury boxes of the amalgamators, which are frequently secured by locked covers. | The following table gives some important details relating to the strakes employed at the Morro Velho mines :— 216 GOLD. TABLE III. %e is _ ep a en "he eae g fs BG ee loa ae E Name ea = 3 DQ wn c2 oe Rs | aa oy of Stamps. el ae 3 c= 5 oe ox om ae Ba gla) | 2 7 ee | 3. | es | ss eae oS oq 2 S mM Qy 5 a| &§ E 4 a & E 4 ie ft. sift; an. cub. ft. liyon *.~.,-1°30 4-36) ST-107 1 a 1,719 | 46°83 | 36°73) 288] 210 | 20°00 Cotesworth | 12} 13| 30 6/1 At 545° | 32°21 | 16°92 104) 65) Be Susannah.| 9] 8/27 O/1 6 324 | 29°61 |-10°94| 48/484 S35 Herring .| 24] 29 hes. -O4ck-i¢ 1,232 | 35°64 | 34°56] 228] 174 | 18:00 Powles;.- 2.06 12:4341-33 e744 34 1,821 | 27°55 | 66°10| 336] 252 | 28°47 Addison (5.1024.1°20 1,31 104 105 1,352 | 38°04 35°54] 240] 170 | 17:00 135 |158 6,993 200°79 }1,244] 919 | 91°72 | My. Dietzsch remarks that straking may, on the whole, be considered a cheap, simple, and economical process, by which 67 per cent. of the gold originally present in the ore is obtained in a highly concentrated state, whilst the 33 per cent. which escapes is in two distinct forms. Ist. Light free gold. 2nd. Gold enclosed in the coarser particles of pyrites. The first, which has, to a great extent, been laminated by the action of the stampers, exposes so great an amount of surface, in proportion to its weight, that it cannot be economically saved by any known process, and floats off with the lighter portions of the slimes. It is difficult to determine the exact amount of loss resulting from this cause, but from experiments which have been made on the residual sands, it is believed to be about 10 per cent, of the gold present in the original ore. The second, which is in the form of fine gold en- closed within particles of pyrites, is partially recovered by separating the coarser from the finer sands, and subsequently grinding them in arrastres, and subjecting the resulting secondary slimes to the action of another system of strakes. fe-treatment of First Tailings—This is effected by running the whole of the waste from the different systems of strakes above described, through ordinary tyes, similar in construction to those represented Plate IV. oc’, in which small wooden stops are from time to time placed at the end, thus allowing the slimes to run off, whilst the coarser sands remain behind, These tyes are arranged VEIN MINING IN BRAZIL. 217 in couples, so that whilst one is being cleaned out, the other may be in operation. When one of these tyes has been thus filled, the sand from it is taken out into another box, from which it is conveyed by a stream of water into arrastres, which have an opening in the side about a foot from the bottom. Into these arrastres, of which there is a series, driven by water power, the coarse sands are constantly flowing, mixed with a stream of water; and becoming ground under the mullers, are so reduced in size as to float, and then escaping through the apertures in the sides, are concentrated on a system of strakes. It is evident that the action of these machines will be continuous, since the supply of sand to be pulverised is constantly flowing in, and being heavier than the finer particles, it will sink to the bottom, where it remains until it has been ground into an impalpable state, when it escapes in suspension over the strakes. ; Each arrastreis supplied with three cubic feet of water per minute, each cubic foot holding in suspension 1°75 Ibs. of sand, and discharges over three strakes, 15 feet in length, covered with either five or six skins. The quantity of sand passed through in the course of twenty-four hours, is about three tons. The deposits collected on the first skin are regarded as head sands, and washed off every two hours into tanks, from which they are sent directly to the amalgamating house. These sands usually contain about 163 dwt. of gold per ton. The deposit on the second skin is removed every four hours, and, like that on the first, subjected to direct amalgamation, whilst the other skins are only washed every twelve hours, and the slimes afterwards subjected to concentration. Below the first series of strakes, a number of extra strakes are laid down, which are worked precisely lke those attached to the first system before the stamping mills. Re-treatment of Second Tailings—Up tothe year 1855, the tailings from the system of apparatus before described were treated as worth- less, and sluiced into the river accordingly, although it had been determined, by numerous experiments, that they still retained a notable amount of gold. At that period, however, a distinct system of works was erected on the banks of the river, and at a low level, for the elaboration of the whole of the refuse escaping from the upper floors. These are provided with a series of tyes, in which the sands are separated from the slimes, and from which they are subsequently 218 GOLD. taken to be again ground in stamping mills and arrastres.* The sand from these tyes contains about 11 dwt. of gold per ton. As these sands could not be advantageously ground in stamping mills, without the admixture of some coarse and hard material, they were for some years stamped with the addition of a portion of a deposit, known as “ Cascalho,” containing small quantities of gold ; but in 1861, the supply of this substance having become to a great extent exhausted, the refuse portions of the lode, picked out at the spalling floors, were substituted for it. The result of this experiment proved highly satisfactory, and consequently the employment of these wastes, which contain a small amount of gold, has been since continued. The system of enrichment on strakes is conducted precisely as in the case of the upper floors, and about 16 cubic feet of concentrated sand is daily produced. These sands, however, contain large quantities of decomposing sulphides, giving rise to the formation of sulphates of iron, which rapidly flour and sicken any mercury brought in contact with them, and the tailings are consequently not adapted for direct amalgamation. They are therefore again further concen- trated, by being passed over another set of strakes, until they have become reduced from 16 to 13 cubic feet, and are then carefully washed -in a batea. This batea is a shallow wooden bowl, used in the same way as the tin dish of the Californian miner, and in which some six or eight pounds of sand are operated on at a time. The product of this last washing chiefly consists of finely-divided gold, associated with small quantities of various mineral impurities, from which it is separated by trituration with mercury in large Wedgewood- ware mortars. Amalgamation of Concentrated Ores—The apparatus employed at Morro Velho is represented Plate VI. In this drawing fig. 1 shows the machinery in elevation, and fig. 2 in plan, whilst fig, 3 is a vertical section of the triturator, or “saxe.” The water-wheel A, by means of intermediate gearing, gives motion: to a set of barrels H, 4 feet in length, and 2 feet 5 inches in diameter, each having a capacity of 20 cubic feet. The charge of each barrel is 16 cubic feet, or one and a half ton of wet sand, and 60 lbs. of mercury. There is also a sufficient amount of clean water at the - * The stamping mills employed at this part of the establishment have no grates, but, like those of Schemnitz, discharge once over sluices or dams. VEIN MINING IN BRAZIL. 219 - same time introduced, to give to the slimes the necessary degree of fluidity to enable the globules of quicksilver formed to become properly incorporated, without allowing them to become sufficiently mobile to admit of the settling of the mercury and amalgam at the bottom. The barrels, when thus charged, are allowed to revolve in accordance with the nature of the ores treated, and the state of the atmosphere at the time, during from thirty to thirty-six hours; and the bungs L, being then removed in succession, the contents of the barrels are dis- charged into the hoppers M. The stop-gates a are now slightly raised, and a small stream of water is introduced into the hoppers, which gradually washes their contents into the spouts N, where an additional supply of clean water is added from the launder F, and the united streams, carrying with them in suspension a portion of the slimes from M, fall into the transverse conduit o, from whence they pass through the funnels 0, into the trough, or saxe w. The saxe consists of a trough, sixteen feet in length, and two feet in width, divided into six compartments by the partitions w, and provided with a movable agitator, or runner v, which can be removed at pleasure by being vertically drawn out of the trough w. This is supplied with rakes, fixed on the faces of solid wooden blocks w’, corresponding to the number of divisions in the saxe, and supported on a bar, running on guide wheels, in such a way, that the depth of the rakes can be easily regulated by means of screws; a certain amount of play being at the same time allowed them by the intro- duction of springs. Motion is given to the rakes by the eccentric Q, and the rods §, U, and bell-crank 1, the rod u being at one end connected with the movable bar of the runner. The working of this apparatus is conducted as follows :—The contents of the barrels are first discharged into the hoppers M, and from thence slowly washed, by a constant stream of water, into the saxe through the funnels 0, traversing the two central runner-blocks, and discharging beneath the surface of the mercury, whilst the rakes are slowly drawn backwards and forwards, by the action of the eccentric Q, over the surface of the mercury, which accumulates in the trough of the saxe w. In this way the globules of quicksilver and amalgam are deposited from the diluted slimes, in the bottom of the various divisions, while the slimes themselves flow regularly through the apertures in 220 GOLD. the divisions, shown by the dotted lines, fig. 3, and, escaping at each end, pass over strakes y, covered in the usual way with bullock skins, | by which a large portion of the mercury, which might otherwise be lost, is collected. It will be observed, by referring to fig. 3, that the central division of the saxe is not, like the others, provided with an aperture; and consequently the slimes entering by one funnel are discharged to the right, while those arriving by the other escape to the left of the apparatus. Extra strakes are arranged below the first, which are worked with the addition of clean water, as in the system of supplementary strakes employed below the stamping mills, and the supply of clean water admitted on the strakes Y is regulated by means of the stop-cocks x. The usual loss of gold per ton of ore treated is, at the St. John d’El Rey mines, estimated at about 2 oitavas or nearly 5 dwt. per ton. The mercury can be drawn off when re- quired, and the amalgam is cleaned up, strained, and retorted every ten days, the gold being then melted into bars. The loss of quicksilver, taken on the average of the last three years, has been 2°923 oz. per ton of ore stamped. The average cost of ex- tracting the mineral from the mine, and its reduction, including every expense incurred by the Company for general management, &e. &e., for the last ten years, has been 25s. per ton; out of which the cost of stamping alone has been 2s. 10d. per ton, SopIumM AMALGAM. The extraction of gold by amalgamation has, hitherto, been often attended with difficulties occasioned by the presence of compounds of sulphur, arsenic, antimony, bismuth, or tellurium in the ores; which by covering the gold with a thin film of tarnish, prevents its entering into combination with mercury. The use of sodium amalgam, how- ever, is stated not only to facilitate amalgamation under such circum- stances, but also to prevent the “sickening” of mercury, which in the presence of certain chemical compounds, and among others sulphate of iron, is apt to take place. It is also claimed for sodium amalgam that by its use the “flouring” of mercury when ground with com- pounds containing sulphur, arsenic, tellurium, &e. may to a great extent be avoided. Two claimants dispute the honour of having first discovered these properties of an amalgam of sodium and mercury, but the truth would appear to be that the discovery was made by each, almost at the same time, and without any knowledge of what was being done by the an uy un ——4 e— a —— ss —— iN i | CE TT OTA MN SBSYDHRHASHTSSRENAHCHRADASOBWA ~ ¥¥ SEN . Mouth of Hand Burg. _ Boxes urder H with, Stop-gate aviront.« _ Launder to conduct sand tromM to O. _ Main sand launder cover Saae W. . Pintory Wheel workang av B. _ Bceatrie working orv awe of P. . Fron Bell-crants connected with GC. . Runner of Saxe _ Stop-gate wv tront of M. d _ Doaistons of Saxe. _ Rakes. heter cence. Water-whee. . Crown Wheel. Piracry Wheel working vB. Wrought Tron’ Shate Saddles tor D. Spout supplyurg wate over NV. Wooderv Cog Wheels fired on D, Wooder Barrds. Brass Cog Wheels fievcod or Handrworking iWwG. \ Movable Saddles tiaed to Kh Lever tor moving J. Trow bar cornecting wah T. Right Angle Bell-cronk. LTrov bar connecting T with V. Jame, Stop Cocks or taps. Sdarv Strakes. Aqueduce bringuig water av M. Pu ae E.& FN. Spon.48,Channg, Cross,London. a8 eT Ht ‘Na LATTA eT I —__ Scale of Feet. SODIUM AMALGAM, 294 and other. Dr. Wurtz of New York applied for an American patent in November 1864, whilst Mr. Crookes made a similar application in England in February 1865, and consequently before anything was known in Europe of the existence of the American patent. It must, however, be conceded that the first application for a patent was un- doubtedly made by Dr. Wurtz. Not having any personal experience of the effects produced by the addition of sodium amalgam to mercury employed for the amal- gamation of gold ores on a large scale, the following description of its action is given on the authority of the inventors of the process, and has been chiefly derived from an article by Dr. Wurtz, published in the American Journal of Science and Arts, vol. xli. March 1866, and from a pamphlet on the same subject, published for private circulation, by Mr. Crookes. It may be remarked that at the date of our leaving the mining districts of California in December 1866, _ although its use had been extensively experimented on, it had not become generally adopted, and that the evidence with regard to its efficiency was considered to be of a conflicting nature. It may, never- theless, be regarded as certain, that no time was lost in practically testing the efficiency of sodiuin amalgam, and that, had it possessed all the advantages claimed, its use would have long since become general. A quantity of sodium amalgam dissolved in a hundred times or more its weight of quicksilver, is said to communicate to the whole a greatly enhanced power of adhering to metals, and particularly to those which, like gold and silver, are situated towards the negative extremity of the electro-chemical ‘scale. This power of adhesion in the case of the two metals is so great, that the resistance which their surfaces, when in their native state, often oppose to amalgama- tion (a resistance much greater, and more general than has been hitherto recognised, and due to causes as yet uninvestigated) is instantly overcome, whether their particles be coarse or impalpable. _ Even an artificial coating of oil or grease, which is usually such an enemy to the combitanen of mercury with other metals, forms no obstacle to immediate amalgamation by this prepared quicksilver. The atoms of quicksilver are, as it is described, put into a sort of polaric condition, by a minute addition of one of the metals which range themselves toward the electro-positive end of the scale; so that its affinity for the more electro-negative metals is stated to be so greatly exalted that it seizes upon, and is instantaneously absorbed by their 222 GOLD. surfaces, Just as water is absorbed by a lump of sugar, or other porous substance soluble in it. . Such quicksilver even adheres strongly to surfaces of iron, steel, platinum, aluminium, and antimony; an adhesion which, however, in the case of these metals is not a true amalgamation, there being no penetration into the substance of the metal; so that the superficially adherent quicksilver may be readily wiped off, just as water may be removed from glass: the only metal as yet experimented on, which cannot be enfilmed by the use of sodium amalgam, appears to be magnesium. Application of Sodium Amalgam to working Ores of the Precious Metals.—This consists in adding from time to time, to the quicksilver used in amalgamation, about one hundredth part of its weight of sodium amalgam. The frequency with which the amalgam is to be added cannot be exactly specified, as it will be found to depend on a multitude of circumstances, such, for instance, as the temperature, the purity and quantity of the water used, the ratio borne by the surface of the quicksilver to its mass, the amount and mode of agitation of the quicksilver, the nature of the process and apparatus used, the character of the ore, strength of the amalgam, &c.; so that this important point can only be determined in each case by ex- perience. Some general indications may, however, be derived from the experiments which have been made. It is said that less sodium is requisite in cases in which much water is employed, and when the water is frequently renewed, as, for instance, in the riffles of a sluice, and in all forms of amalgamators through which a continual current of water is kept running ; since mercurial solutions of sodium are but little affected by water free from acid, alkaline, or saline impurities. In cases, however, in which but little water is employed, and especially where the ore and quicksilver are ground together into a slime, the water soon becomes alkaline, and oxidation of the sodium sets in, necessitating its frequent renewal. In such cases the following mani- pulation is recommended. The whole amount of quicksilver to be used for working up a batch of slimes, say fifty pounds, is prepared by dissolving in it one per cent. of amalgam No. 2; or better, two per cent. of the soft amalgam No. 1, which dissolves more readily: * one- * No. 1 amalgam contains two per cent., and No. 2, four per cent. of sodium, and is a hard brittle solid, remarkably infusible, requiring a temperature nearly as high as the fusing point of type metal to melt it, and may be cast into ingots, and packed either under petroleum, or in air-tight iron cans filled with dry lime, SODIUM AMALGAM. 9238 half, or twenty-five pounds, is then thrown into the mill with the ore, and as the incorporation proceeds ; certain fractional parts of the other half are added at intervals, varying according to circumstances, until the whole has been introduced. If, as is usual, the quicksilver has been separated from the slimes of a previous operation, it will retain a certain amount of sodium, and therefore require fresh amalgam in proportionately smaller quantities. In sluicing operations, the soft amalgam No. 1 is, on account of its ready solubility in mercury, most recommended ; and in these cases it is practicable to test the quicksilver in the riffles, and ascertain when the magnetic quality requires restoration, by throwing in a few grains of gold dust.* Similar tests are easily applied to slimes, and in amalgamating generally, a slip of tarnished sheet copper is a suitable agent for such testings. It may be remarked that the amalgam No. 1 is at any time easily prepared from No. 2, by melting it in an iron ladle with its own weight of quicksilver. In copper-plate amalgamation,—that is, in cases in which auriferous materials are brought into contact with amalgamated metallic surfaces,—it is recommended to substitute for quicksilver itself the pasty amalgam No. 2. In these modes of amalgamation great economy in wear and tear of apparatus, as well as in first cost, is said to be effected by using plates or surfaces of iron instead of copper. The power of coating or enfilming iron is stated to render these amalgams peculiarly valuable in every form of apparatus for amalgamation, which has internal surfaces of iron; for these becoming coated with quicksilver immensely extend its chances of contact with particles of gold, so fine as to remain suspended in the water. Other important services are expected by the inventors to arise out of this power of enfilming iron, such as keeping the surfaces of stamps and of other apparatus used in crushing ores continually coated. In like manner, as the power of adhesion of quicksilver to other metals is exalted by the presence of the alkali-metals, so also is its own cohesion stated to be greatly increased. It is rendered more difficult to mechanically divide, and when thus divided again runs instantly together upon contact. Hence new results of great value are said to have been obtained. For instance, the so-called flouring or granula- tion of quicksilver, which in the amalgamation of ores always occa- * From the attraction which it appears to possess for other metals, Dr, Wurtz calls the compound of sodium and quicksilver, “ Magnetic Amalgam.” 224 GOLD. sions losses both of the quicksilver itself, and of its amalgams with the precious metals, is stated to be reduced to a minimum, or alto- gether prevented. The recovery of floured quicksilver and amalgams from slimes and similar mixtures, is also said to be greatly facilitated and accelerated thereby. For this purpose some sodium amalgam is thrown into the separator, and collects and incorporates all the scattered globules of auriferous amalgam. It is here necessary to call attention to a method of manipulation generally applicable when sodium amalgams are used, and particularly so in all cases in which the ore is ground or agitated with quicksilver in contact with metallic iron. This arises from the liability of abraded particles of iron to adhere to the amalgam. The following plan is therefore in such cases recommended. The amalgam, after separation from excess of quicksilver, and before retorting, is fused in an earthen dish or iron Jadle, with, if necessary, addition of a little quicksilver to make it more quid; and the iron, which forms a scum on the surface, is skimmed off. The excess of quicksilver may, after cooling, be again separated from the amalgam in the usual way. Any amalgam which adheres to the iron scum is readily detached by boiling in water to remove the sodium. This process depends on the fact that adhesion to the iron totally disappears with the extraction of the last traces of sodium from the quick- silver. It is in fact possible to remove all iron from the amalgam by boiling in water without any previous fusion, particularly if the water be made somewhat acid or alkaline. The presence of iron can be readily detected by the magnet, which may also be sometimes used with advantage in separating iron from amalgam after all the sodium has been extracted. There are still other substances which may be found adherent to the amalgam when sodium has been used, such as platinum and osmiridium. These, like iron, immediately detach them- selves on the removal of the sodium by boiling the amalgam in water. A mixture of platinum, or osmiridium, or both, with iron, may be freed from the latter by the magnet. The sodium amalgams prepared in this country in accordance with the recipes of Mr. Crookes, and sold by his agents, are known re- spectively as A, B, and C amalgams. | Each of these contains three per cent. of sodium, in addition to which B has a small quantity of zine in its composition, and C a little tin. An amalgam (A), of seven times the strength of the above, SODIUM AMALGAM, 295 is prepared in solid bars for shipment when the expense of freight or land carriage is great. Amalgams B and C cannot be prepared in the concentrated form. It is recommended that one part by weight of amalgam B or C be dissolved in thirty parts of the mercury which is to be used in the amalgamating, triturating, or grinding machines, and the effect which it produces on the mercury noted from time to time during the operation. If it retain its fluidity and brightness to the end of the operation, it is a sign either that a sufficient amount, or too much has been added, and a second experiment should be tried with a less quantity of amalgam. But if it be floured, or sickened, or any loss occur, more amalgam may be added until the best propor- tion is arrived at. Mr. Crookes states that amalgam B will generally be found effective, but if the ore contain an excess of any mineral which has a deleterious action on mercury, more especially if it contain bismuth, it will be advantageous to employ amalgam OC instead of B. When the best proportion of amalgam B or C is determined, small quantities of amalgam A should be introduced into the mercury, already containing amalgam B or GC, in the proportion of one part of amalgam A to one thousand of mercury. This quantity of amalgam A can be added every few hours, according to circumstances, but one charge of amalgam B or C will, it is stated, usually be suffi- cient for several days. Under some circumstances it will be found advisable to add amalgam B or C every few days, but a little ex- perience, and comparison with the results obtained by the old plan, will soon show how these several agents are best utilised. CHAPTER XI. ASSAY OF AURIFEROUS ORES—ESTIMATION OF GOLD CON- TAINED IN QUARTZ—REFINING—ASSAY OF GOLD BULLION. ASSAY OF GOLD QUARTZ—FUSION WITH LITHARGE OR RED LEAD — AURIFEROUS PYRITES — CUPELLATION — INQUARTATION — PARTING— ASSAY TABLE — TABLE SHOWING PROPORTION OF GOLD IN AURIFEROUS QUARTZ—REFINING—PLATINUM » VESSELS—CAST IRON PANS—ASSAY OF BULLION—QUANTITY OF LEAD NECESSARY FOR CUPELLATION OF ALLOYS OF GOLD AND COPPER—ASSAY LABORATORY— THE TOUCHSTONE, Assay oF AURIFEROUS OrES.—Although the exact amount of gold contained in a given specimen of rock is readily ascertained, it is often much more difficult to obtain a fair average.sample of the whole produce of a vein. When the gold is in a finely-divided state, and equally disseminated throughout the rock, this presents compara- tively little difficulty ; but when, on the contrary, it is granular, and occurs in pockets and irregular deposits, great care and labour are sometimes necessary in order to obtain representative samples of the mass. It is, therefore, of the highest importance that whenever rock is to be assayed for gold, the greatest care should be observed in preparing the samples on which the operation is to be subsequently conducted. With this view, the rock, of which it is desired to ascertain the yield, should be broken, and the heap cut through in the usual way, at least a ton being taken from each pile of importance, and reduced to fragments of the size of beans. This may be done, where machinery for dry crushing is not at hand, by means of a flat-faced hammer on an iron” plate. After well mixing, this pounded ore is again cut through, and about ten pounds of it taken for the purpose of being still further reduced in size, and passed through a sieve of fine wire gauze ; on this last from three to six different assays are made, and their mean result taken as the produce of the rock examined. By operating in this way a great degree of accuracy may be ensured; but where a less amount of exactitude is required, the quantities of rock crushed may be somewhat reduced, and the number of assays made, fewer. Instead of operating as above described, a given weight of ASSAY OF AURIFEROUS ORES. 2917 finely-powdered rock, from the last cutting, may be reduced in volume by careful washing in a batea, and the residue dried, and assayed in the usual way. From the results obtained, the amount of gold present in a ton of original rock can be readily calculated. In establishments for the crushing and amalgamation of auriferous rock, it is, however, generally of more importance to determine the amount of gold retained by the tailings, than to ascertain by assay the . actual produce of the original ore; since the quantity yielded by amalgamation on the large scale, added to that present in the result- ing sands and slimes, will, for many practical purposes, sufficiently represent the total contents of the rock. It is also desirable to know exactly the amount of gold carried off in the final tailings, in order, not only to be enabled to judge of the effect of any modifications which may have been introduced in the machinery or methods of working, but also for the purpose of ascertaining if due attention has been exercised during the various stages of the different processes to which the ore has been subjected. When required for this purpose, the tailings should be caught at regular intervals throughout the day, by placing a bucket, or some other convenient vessel, under the spout from which they finally make their escape; and when full of water and sand, it must be placed aside, in order to give the matters in suspension time to settle. As soon as the water in the bucket has deposited the whole of the solid matter which it held in suspension, it is carefully decanted off, and the deposit, accumulated at the bottom, removed into a box prepared for that purpose. This is repeated at intervals of about two hours, and at the termi- nation of the experiment the contents of the box are dried, thoroughly mixed and submitted to assay. In the case of samples of tailings thus obtained, the discrepancies between the several assays will, in general, not be very considerable, since the coarse particles of gold will, as a rule, have been retained by the blankets and other appliances over which the stamped rock has passed, and the remaining fine gold is dis- seminated with a considerable degree of regularity throughout the mass. Fusion with Litharge or Red Lead.—When the rock to be operated on does not contain an appreciable quantity of iron pyrites, or any other metallic sulphide, weigh 600 gr. in a finely-pulverised state, and inti- mately mix it with 4,000 gr. of litharge or red lead, and from 15 to 20 gr. of flour, starch, or finely-powdered charcoal.* Introduce this into a * The weight of pounded ore is fixed at 600 grains, because this quantity can be easily fused in an ordinary No. 10 French crucible. Q 2 228 GOLD. crucible, of which it should occupy about one-half the capacity, and heat it in an ordinary assay furnace, until the whole has entered into a state of perfect fusion, when the crucible is withdrawn and allowed to cool. When sufficiently cold, it is broken, and the button of lead extracted, cleaned, and cupelled. In the case of ores containing a large amount of gold, it is far better to break the crucible than to pour its contents into an iron mould; but in works in which tailings are being daily examined, the practice of pouring assays may be adopted with advantage, as from the smallness of the quantity of gold contained in the material operated on, no appreciable error will be the result, whilst, on the other hand, the saving in crucibles will be considerable. In quartz-crushing establishments generally, the assays of ores and tailings may be conveniently conducted in the furnace employed for retorting and melting, which is generally of sufficient size to admit of three or four fusions being carried on at the same time. In regular metallurgical laboratories, for the sake of durability, and to prevent the cracking of the brickwork, the outside of the melting furnace is usually secured by iron plates as shown Fig. 37, which repre- sents that employed by Mr. F. Claudet, and in which A a’ are the fire- places, B B’ the fire-bars, and 6 b' the ash-pits. The dampers C C’ permit of regulating the draught, and the mouths of the furnaces are closed by the hinged doors D D’, lined with baftle-plates. Instead of hinged doors, sliding plates are sometimes employed, and are, for general purposes, probably preferable. The dimensions of this furnace ave, 10 inches square and 16 inches in depth above the fire bars, which can, when necessary, be drawn out from the front for the purpose of allowing the coke to fall into the ash-pits 0 0’, or for unclinkering the erate. When used with charcoal, the crucibles must be supported on the bars on pieces of firebrick; but when coke is employed, it has in itself sufficient resistance to allow of their being embedded in the fuel without any other support. The best crucibles for this purpose are ordinary French pots, which, before being introduced into the fireplace, should be annealed by being gradually heated on the top of the furnace, in order to expel any moisture they may have imbibed, and which, if they were too suddenly heated, might cause them to crack. . When, in addition to gold, the rock contains iron pyrites or any other sulphurised mineral, it frequently happens that the admixture of charcoal. becomes unnecessary, and the fusion may be. made with litharge alone, since one part of iron pyrites reduces eight and a half ASSAY OF AURIFEROUS ORES. 229 parts, blende seven parts, and sulphide of antimony, or grey copper ore, about six parts of lead, to the metallic state jin ce ae IN LA | Hl eo AS | CA ATAU TAR ie ull | Hh} Hy NN Mil a Aa FATE it "na a RRL vee AN | t ee r ie. 7 ' ne “i 11 sane rion MN Ta lj —— isl co TT aa | eam —= UIA sre HIN | | Hi i i um, : , pens | | | | | nl ‘a i . - : = ia a ! \ mm TM Th | | vest ‘ | i | | | ! » q iS ham / | | Hil il CCT i HI GOTT HAT —— \ I} TN ——— | WH = et! MAN iH | ——— — He =a = i 1 ee \ | M4 OS iil —— = 1 = wn Mt ! INT —_ fn im ——— cc 5 UREA NEPEDUOTO WOON OW ONAD ON ORONOQOOONEOUOOQUBNGUE TTT TTT TT TT TTT AAD OQRUOAQUGOOQROVOOCOSQQQUNEQTOONNOSIOOOH CLA | il a TN A (8 ——/ ——— ae mi 4 iD Ep MELTING AND Waday NES Auriferous Pyrites—To determine the amount of gold contained in quartz much mixed with iron pyrites or other metallic sulphides, 230 GOLD; or to assay auriferous pyrites resulting from the concentration of tailings, the following process is generally resorted to. The amount of the substance on which it has been determined to operate, is weighed into a shallow scorifier, and then introduced into the mouth of the muffle of the cupelling furnace, care being taken not to heat it at first too strongly. The powdered ore is from time to time stirred with a bent iron wire fitted into a wooden handle, and in proportion as the sulphur is evolved, and the substance becomes less fusible, the scorifier is pushed further into the muffle, and consequently subjected to a higher temperature; the stirring, by means of the iron rod, being at the same time continued. The roasting must thus be carried on until all odour of sulphur has ceased to be evolved, and the scorifier with its contents is then withdrawn, and allowed to cool. When sufficiently cold, the roasted ore is united with six times its weight of litharge, its own weight of dry borax, and from fifteen to twenty grains of charcoal, and the whole fused in the furnace as above described. In making the addition of the reducing agent it is necessary to add such a quantity as will afford a button of lead suthi- ciently large for the collection of the whole of the gold present, and at the same time of a size convenient for cupellation, since, if the amount of lead were too small, a loss of gold would be the result, whilst a very heavy button would require a large cupel, and occupy a long time in working off.* Cupellation—This process is founded on the circumstance that when an alloy of lead and silver, lead and gold, or of lead, silver, and gold, is exposed in a state of fusion to the action of a current of air, the precious metals are neither perceptibly volatilised, nor become oxidised, whilst the lead rapidly absorbs oxygen with the formation of a readily-fusible oxide. In order, therefore, to obtain the gold and silver contained in the assay buttons, it is merely necessary to expose them, on a porous fire-proof support, to such a temperature as will cause the oxidation of the lead, whilst the precious metals are not so affected. The ltharge thus produced is absorbed by the porous body on which the assay is supported, and nothing but a button of gold or silver, or of an alloy of the two, in case of their being both present, ultimately remains on the test. These supports, which are called cuwpels, are made of bone-ash slightly moistened with water, and consolidated, by pressure in an iron mould, into the required form. 3 * Instead of operating as above, the assay may be made by scorification.—See Assay of Silver Ores. ASSAY OF AURIFEROUS ORES. oat Cupels should be perfectly dry before being used, and ought to be kept for at least a fortnight in a warm place in the laboratory, pre- vious to being employed for making cupellations. The muffle, which is made of baked fireclay, has the form of a small D-shaped retort, closed at one end, and is generally provided with openings in the sides and ends, in order to allow of the circulation of air through it. | The furnaces used for cupellation differ considerably in shape and method of construction, but the muffle, when fixed, is so arranged that whilst its closed extremity is supported by a proper shelf, the other corresponds with an opening in the front of the furnace, to the sides of which it is luted with a little clay, and has before it a small platform, on which the hot cupels can be allowed to stand when with- drawn from the muffle.* The muffle thus placed can be equally heated in every part, whilst the apertures, in the sides and end, admit of the passage through it of a current of air from the mouth, through the interior of the muffle, into the furnace itself. To light this apparatus, a little ignited charcoal or coke is thrown into the furnace, which is afterwards filled with fuel; and as soon as the muffle has become heated to bright redness, six or eight cupels, that have been annealing at the mouth of the opening, are introduced by means of proper tongs; the bottom of the muffle having been previously covered with a little loose bone-ash to prevent its being attacked in case of any litharge passing through the cupels in the course of subsequent operations, The open end of the muffle is now closed by a tile or door provided for that purpose, to prevent the introduction of cold air, and the cupels are raised to the temperature of the muffle itself. When this takes place, the door is removed, and a button, obtained from the fusion with litharge, introduced into each of the cupels by a pair of slender tongs. The mouth of the muffle may now be again closed for about a minute, in order to facilitate the fusion of the alloy ; and on its removal, each of the cupels will be found to contain a bright metallic bath, in which state the assay is said to be wncovered. Under these circumstances, the lead is rapidly converted into litharge, which is absorbed by the cupel as quickly as it is formed, whilst at the same time a little white vapour rises from the cupels, and is gradually carried off through the end, and through the openings in the sides. A circular stain is at the same time formed around the metal in the cupels, * The best fuel for the cupelling furnace is hard coke broken into small pieces. 232 SaCOLD: which gradually extends and penetrates into their substance. When nearly the whole of the lead has been thus removed, the remaining bead of rich alloy appears to become agitated by a rapid circular motion, which seems to make it revolve with great rapidity. At this stage, the rotation of the bead will be observed to cease, and the button, having for an instant emitted a bright flash of hght, becomes suddenly immovable. This is called the brightening, and a button remains on the cupel, composed of an alloy of gold, with the silver derived from the litharge, added to that which may have originally existed in the ore operated on. When the proportion of silver is, in comparison with that of gold, very considerable, and the button of alloy is itself a large one, the abrupt removal of the cupel from the muffle might cause the metallic bead to spirt or vegetate, by which a portion of the metal might be thrown off, and a certain amount of loss thereby entailed. To prevent this taking place when a large button has been obtained, the cupel must be gradually withdrawn towards the mouth of the muffle; or the cupel in which the assay has brightened, may be covered by another, kept hot for the purpose, and then removed to the small platform in front of the muffle. From the fact that silver becomes sensibly volatile at very-elevated temperatures, it becomes necessary, when this metal is present, to make the cupellations at the lowest possible heat at which they can be effected. The temperature best fitted for this operation is obtained when the muffle is at a full red heat and the vapours which arise from the assays curl gradually away, and are finally removed by the draught. When the muffle is heated to whiteness, and vapours rise to the top of the arch, the heat is too great; and when, on the contrary, the fumes lie over the bottom, and the sides of the openings in the muffle begin to darken, a little more fuel must be added, or the draught increased. Should the temperature fall below this point, and the lead se¢ in the cupels, they may generally be again started by closing the mouth of the muffle with a few large pieces of charcoal. These should be removed when the complete fusion of the alloy in the cupels has been again effected. If an assay has been properly conducted, the button obtained is round, bright, and smooth on its upper surface, and is readily removed from the cupel. Pi Inquartation.—In order to be enabled to completely remove silver from an alloy of that metal with gold, by the use of nitric acid, it is essential that the weight of the silver present should be about three ASSAY OF AURIFEROUS ORES. Zoe times that of the gold. It is consequently necessary that when the amount of gold in the button of lead is approximately known, a piece of pure silver should be added to it before cupellation, of such a weight, that with the quantity of that metal derived from the litharge (ascertained by a separate assay) it will, as nearly as possible, fulfil these conditions. The only inconvenience, however, attending the addition of too large a proportion of silver is, that the gold obtained by the subsequent action of acid is thereby rendered flocculent, and somewhat more difficult to collect. When the object of the assay is to ascertain only the amount of gold present, without estimating the associated silver, the necessary addition of this metal is best made by placing a piece of the required weight on the leaden button obtained from the fusion with litharge, and driving it into the lead by a blow with a bright-faced hammer. In the case of poor ores, containing less than 10 dwt. of gold per ton, the silver derived from the litharge will of itself frequently be sufficient for the purpose of inquartation, whilst, as before stated, for the estimation of gold in richer ores, the addition of a little pure silver before placing the leaden button in the cupel becomes necessary. When the ore treated contains silver in addition to gold, and it is desirable to ascertain its amount, it becomes necessary to first cupel the button of lead without the addition of silver: the metallic globule thus obtained is weighed, and its weight noted, as is also that of the amount of silver derived from the reduced litharge. If neces- sary for the operation of parting, more silver is now added by folding the globule obtained from the cupel, together with a bit of silver, in lead foil, and again passing it to the cupel. Lastly, the button of alloy resulting from the second cupellation, is dissolved in nitric acid, and the gold weighed. The amount of silver present in the ore will con- sequently be represented by the weight of the button of allov obtained from the first cupellation, less the united weights of the gold, and of the silver yielded by the reduced litharge. Parting.—The button obtained by cupellation is first allowed to cool, squeezed laterally between the jaws of a pair of strong pliers, and brushed with a hard brush to remove any adhering litharge, and then flattened by a bright-faced hammer on a steel anvil. After being carefully examined, in order to ascertain that it is perfectly free from extraneous matter, the flattened button is taken between the points of a pair of steel forceps, and dropped either into a long-necked flask of about two ounces’ capacity, or into a large test- 234 GOLD. tube, and about half an ounce of nitric acid of 22° Baumé =1:18 sp. gr. perfectly free from any trace of hydrochloric acid, added. The acid must now be boiled over a spirit lamp or gas jet, until all action on the alloy has ceased, and the liquid carefully decanted off. About a quarter of an ounce of pure nitric acid of 32° B.=1:28 sp.gr. is then introduced, and boiled for about ten minutes, when it is, in its turn, poured off, and the flask or tube filled with distilled water. Its mouth is now covered by a small crucible, and its position reversed in such a way, that the gold which it contains may fall through the water into the crucible beneath it; and when this has taken place, its mouth is raised to the surface of the water in the crucible, and by a sidelong movement withdrawn altogether from it. The water is now carefully decanted off, and the crucible laid in a hot place to dry, after which it is heated to redness in the muffle, and when cold the gold is removed and weighed. Instead of using a flask, a thin crucible of porcelain may be employed for the operation. Wetghing—The balance employed for assays of gold and silver should weigh to one-thousandth of a grain, and be provided with a set of decimal grain weights. A good balance should be fitted with an apparatus for steadying the pans, connected with the axis which moves the beam, in such a way that one movement of the handle first releases the beam, and subsequently the pans. The knife-edges should be made of agate, so that all the working parts may be enabled to resist injury from the fumes of the laboratory, or the effects of a damp climate. The beam of such a balance ought not to be Jess than eight inches in length, and must be divided for the use of a sliding weight moved by an apparatus provided for the purpose. The whole is enclosed in a glass case supported by adjusting screws for placing the instrument level. To prevent wearing, the weights should be handled by the aid of a pair of forceps provided with ivory points. 2 From the result obtained by weighing the gold yielded by- assay, the amount contained in a ton of ore of 20 cwt. may be readily calculated, either directly or by the aid of the following table — bo oo rt ASSAY OF AURIFEROUS ORES. TABLE Showing, from the weight of Metal obtained from an Assay on 600 grains, the amount of Gold in oz. dwt. and gr. contained in a ton of Ore.* If 600 grains | One ton of Ore will || If 600 grains | One ton of Ore will of Ore give yield of Ore give yield Fine Metal, Fine Metal, Fine Metal, Fine Metal. gr. oz. dwt. gr. gr. oz. dwt. gr. 0001 5H te ee 2 0°100 ae ak 0°002 | O24 0°200 10, 172, 28 0003 Oe a 6 0°300 16) G16 0004 0 4 8 0°400 21 15 13 0-005 0 5 10 0500 27 410 0°006 0 612 0°600 32.13 8 0°007 Peay peg Ce 0°700 ao) 52.15 0008 A ae 0800 43 11 2 0009 0° 9 19 0°900 49 0 0 0°010 0 10 18 1:000 54 8 21 0°020 Dols 2°000 108 17 18 0030 PZ-16 3°000 163 6 16 0°040 2 3138 4°000 217 15 13 0°050 2 14 10 5°000 272 4 11 0060 ay D'S 6°000 326 13 8 0°070 So t6 5 7°000 381 2 5 0-080 eis 8000 435 1l 2 0°090 418 0O 9°000 490 0 O To FIND THE WEIGHT OF GOLD IN A MIXTURE OF THAT METAL AND QuARtTz.—In purchasing fragments of rich gold quartz, it is sometimes desirable to be enabled to ascertain their intrinsic value, without separating the gold, and thereby destroying the specimen. From the * To use this table, write beneath each other, on a slip of paper, the number of oz. dwt. and gr. corresponding to the several decimal figures obtained by weighing, and add them together for the yield per ton of ore. As an example, let it be sup- posed that the gold resulting from an assay, on 6V0 gr. of ore, weighs 0°235 gr. On consulting the table we find— _ gr. oz. dwt. gr. OU 8. es aoe nae ed VUES Leal. eva ane. oer eee d oe Bis Ve ES CARES Fe Oa an hms ew Ae 12 15 20 as the yield of gold per ton of ore. 236 GOLD. known specific gravities of gold and quartz, it becomes easy, after determining the density of the mass, to ascertain approximately the. amount of each present in any particular specimen. The following Table exhibits the proportion, by weight, of gold in auriferous quartz of a given specific gravity ; the formula from which it was calculated being found as follows :— Let g be the specific gravity of gold (taken as 19). gq * of quartz (taken as 2°6). m RS + of the unknown mixture. « the unknown proportionate bulk of gold, to a unit of bulk of the mixture. Then zg is the proportionate weight of gold, and (1—~«)q is the proportionate weight of quartz, and of course the sum of these must give the weight of the unit of mixture. That is to say, vg7-+(1—a)q=m. This is a simple equation, from which we find « = rat for the proportionate bulk of the gold. The proportionate weight is ae or ; J 4g a. m —q The formula may be verified as fee Let y be the proportionate weight of the gold. Then : is its bulk, and } ; —¥ the bulk of the quartz. Hence the bulk of the mixture 2 4 au as , which gives y = = = g g 19°6 =— — =1'1585366 ; and the logarithm of- —g?t 164 as before. With the values erie Aes 5 the fraction is 0°06391. The table is read thus: Auriferous quartz, whose specific gravity is 5°2, con- tains 0°5793 of its weight of gold; or, which is the same thing, 10,000 ounces of the quartz contain 5°793 ounces of gold. TABLE Showing the proportionate weight of Gold in a mass of auriferous Quartz, when the specific gravity of the mass is known. Specific | Proportion -|| Specific} Proportion || Specific | Proportion |] Specific | Proportion | Gravity. of Gold. Gravity. of Gold. Gravity. of Gold. Gravity. of Gold, 2°6 0°0000 37 0°3444 52 0°5793 8°5 0°8042 2°65 0°0219 || 3°8 (0°3659 5'4 0°6007 9°0 0°8239 2°7 0°0429 39 0°3862 5°6 0°6206 9°5 0°8415 2°75 070632 4°0 0°4055 5°8 0°6392 || 10°0 0°8573 2°8 0°0828 A’l 0°4239 6°0 0°6565 10°5 0°8717 2°85 0°1016 42.) 0°4413 6°2 0°6727 £150 0°8847 2°9 071198 4°3 0°4580 6°4 0°6879 11°5 0°8966 2°95 01375 | 4:4 0°4739 6°6 0°7021 12°0 0°'9075 3°0 01545 =| 4°5 0°4892 6°8 0°7156 13°0 0°9268 o'1 01869 || 46 0°5037 70 0°7282 14:0 0°9434 32 02172 || 47 | 05176 72 | 0°7402 150 | 0:9577 3°3 0°2458 || 4°8 0°5310 74 0°7515 16°0 0°9703 3°4 02726 || 49 | 65438 76 | 0°7622 17:0 | 0°9813 | 35 0°2979 50 | O-5561 78 | 07724 || 180 | o-9912 | 36 | 03218 511 | o-5679 8:0 | 0°7820 | 19:0 | 1:0000 a_,_ to oN) REFINING. 37 REFINING.--SEPARATION OF GOLD AND SILVER.—The silver produced from some of the mines of the American continent, ancient European ° money, old Mexican and Peruvian dollars, and bars obtained from goldsmiths’ sweep, are composed of silver which usually contains a certain proportion of both copper and gold. The processes for the separation of these metals from each other have been rendered so inexpensive and simple, that bars containing but half a thousandth of gold can now be refined at a profit.* The auriferous silver is first melted, and granulated by being poured into water, and then attacked by boiling in a platinum vessel with from two to two and a half times its weight of sulphuric acid of 66° Baumé. Each attack is made on about 80 lbs. of the granulated alloy, and occupies from three to four hours; the operation being considered finished when effervescence has ceased, and sulphuric acid begins to be evolved. The attack of the granulated alloy by sulphuric acid is necessarily attended with a copious evolution of sulphurous acid gas, which is generally allowed to escape into the atmosphere, but may be con- ducted into a sulphuric acid chamber, and thus utilised. Before passing into the air, or into a sulphuric acid chamber, the eases and vapours are conducted for a distance of some 20 or 30 feet through a leaden tube into a receiver of the same metal, for the pur- pose of condensing the sulphuric acid distilled off, together with a certain amount of sulphate of silver mechanically drawn over with it. This liquid, which contains large quantities of sulphuric acid in solu- tion, marks from 40° to 45° on Baumée’s scale. When the attack on the granulated metal is terminated, from 4 lbs. to 5lbs. of sulphuric acid of 58°, derived from the concentration of acid liquors obtained during the preparation of sulphate of copper, are introduced into the boiler, and, after being boiled for a few minutes, the vessel is withdrawn from the fire, and its contents allowed to settle. In this way the gold falls to the bottom; the supernatant liquer is decanted off into another receiver, and diluted with water until it marks from 25° to 30° on the hydrometer. This solution is now introduced into a large leaden cistern, heated by steam, in which are hung copper plates, by which the silver is precipitated in the form of minute granular crystals. In order to * When gold bullion is refined, it must be alloyed with sufficient silver to make the proportion of gold as 1:23. It is then granulated and treated in the same way as silver bars containing gold. 238 GOLD. ascertain when the whole of the silver has been precipitated, a little of the liquor is filtered, and tested with a solution of common salt; when no further turbidity is caused by its introduction, it is evident that no traces of silver remain in the liquid. In some establishments the liquor is drawn off into leaden reservoirs, where it is allowed to remain in contact with copper plates during several days, in order that the last traces of silver may become precipitated. When the argentiferous and auriferous alloy is very impure, the solution in sulphuric acid is often turbid, and gives rise to deposits in the bottoms of the vessels in which it is allowed to stand. These sediments are transferred to a separate boiler, diluted with water, and precipitated by sheets of copper. The precipitate thus obtained is then washed and dried, and, after being melted and granulated, is again treated by sulphuric acid. The clear solutions obtained in this way are subsequently transferred to the vessels in which the precipitation of silver is effected. In some cases, instead of proceeding as above described, the muddy deposits are first washed with warm water, and then allowed to settle. The residue, which principally consists of a mixture of gold and me- tallic sulphates, is filtered, and then boiled in a platinum vessel with sulphuric acid; by which means a clear solution of silver is obtained, and the gold is deposited at the bottom of the vessel. This is again treated with sulphuric acid, after which it is sufficiently pure to be run into ingots, whilst the solution of silver is transferred to the precipitating tank. When, instead of using platinum vessels, cast iron boilers are em- ployed, the alloy to be attacked may be either in a granulated form or in the state of ingots, and the operation can be conducted on from five to ten cwt. of metal at a time. If this method be adopted, acid of a less degree of purity may be employed; and it is also found that solution is effected in cast iron vessels with a less expenditure of acid than when platinum is the material used. The solutions are transferred in an almost boiling state from the iron vessels in which they have been prepared, to a leaden tank, which is afterwards filled up to about two-thirds its capacity with mother liquors from the crystallisation of sulphate of copper. A jet of loose steam is introduced into the tank, and the liquor boiled until it has become saturated with sulphate of silver. When this takes place, the steam is turned off, and the liquid, after standing an hour to settie, is drawn, either by a syphon or tap, placed about ten inches from the REFINING. 239 bottom, into the precipitating vat. After several successive washings, the gold is removed, again boiled with sulphuric acid in a platinum vessel, and then melted into bars. The silver precipitated by copper plates is carefully washed and dried in an iron pan over a coke fire, or is formed into blocks by means of an hydraulic press. These must be gradually heated before being fused, as they invariably retain a considerable amount of moisture, and might cause the crucibles to crack if at once introduced into them. When sufficiently dry, the compressed silver is fused into ingots. The silver thus refined contains an inappreciable amount only of gold, but is still alloyed with about two thousandths of copper. In most instances the gold obtained by treatment with sulphuric acid is again boiled, in the same way, in a platinum vessel with fresh acid, and then melted into bars. In some cases the alloy is fused with three times its weight of silver, treated with nitric acid, and the residue, after being carefully washed, melted into bars. The ingots obtained at refineries working as above described generally contain about 998 thousandths of gold. The acid solution of sulphate of copper obtained by decantation from the crystals of precipitated silver, contains, in addition to the copper originally present in the alloy, that which corresponds to the amount of sulphate of silver decomposed by the copper plates. This is evaporated in leaden vessels, until it marks 40° Baumé ; when, on cooling, it deposits pale blue crystals, which contain a less amount of water of crystallisation than ordinary sulphate of copper. By means of successive evaporations, the mother liquor furnishes other crops of crystals of sulphate of copper; and, finally, a dark-coloured liquid, of from 52° to 58° Baumé, is obtained, which chiefly consists of dilute sulphuric acid, and is employed in the course of succeeding operations. Sulphate of copper, which has crystallised from solutions containing a large excess of ‘sulphuric acid, is not of a marketable quality, but requires to be dissolved in water, and re-crystallised, when it affords the usual crystals of a deep blue colour, containing five equivalents of water of crystallisation. The crystallisers are of wood, lined with lead, three feet wide, three feet deep, and four feet six inches in length. The floor of the crystallising house is of lead, and provided with gutters for carrying off, into suitable reservoirs, any liquors that may be accidentally spilt. Some experiments made in the Lille Mint, with the view of substi- 240 : GOLD. tuting iron’ for copper plates in the process of refining, did not, on the whole, afford satisfactory results. : When the proportion of silver in the alloy does not amount to from 20 to 30 per cent. of the whole, instead of treating it directly by sulphuric acid, it is first granulated, and roasted in a furnace at a low red heat. The oxidised mixture is afterwards boiled in the weak acid liquors from the crystallisation of sulphate of copper, by which a portion of the copper is removed, and the residue subsequently refined in the usual way. | ASsAy oF GOLD BULLION.—The process employed for assaying gold bullion by the assayers of the Mint and the Bank of England is similar to that employed at the Paris Mint, and the weight operated on is often the same. One-half gramme is accurately weighed, and subjected to cupellation with a proper quantity of lead, and a portion of pure silver, about three times the weight of the gold supposed to be present in the alloy. The resulting button is then flattened into a disc, about the size of a sixpence, and, after being annealed, is passed through a flatting-mill until it has been drawn into a riband from 24 to 3 inches long, which is again annealed, and coiled into a spiral by rolling between the finger and thumb. The cornet is now introduced into a long-necked flask, containing about an ounce of pure nitric acid, of 22° Baumé = 1:18 sp. gr., and boiled until red fumes have ceased to be evolved. This acid is carefully poured off, and the cornet again twice boiled, for about ten minutes each time, with acid of 32° Baumé = 1°28 sp. gr. In the two last boilings, a piece of charcoal, consisting of half a charred lentil, is introduced into the flask for the purpose of preventing the ebullition from taking place irregularly and with sudden bursts, which would be liable to break the cornet and project a portion of the liquid out of the flask. After this second attack, the cornet is washed twice with distilled water. The flask is then filled with water, and reversed, with care, into a small crucible of fine clay, into which the cornet is allowed to: fall, gently and without breaking. The water which covers the cornet is now poured off, and the crucible and its contents are heated to redness in the muffle; taking care, however, not to raise the tempe- rature sufficiently to cause the fusion of the gold. From the weight of the cornet obtained, the fineness of the alloy is calculated. The cornet, after boiling in nitric acid, is of a spongy texture, of a ASSAY OF GOLD BULLION. 24] brownish-yellow colour, and exceedingly fragile, so that it. would ‘be impossible, in this state, to touch it with the fingers without breaking it; and it is consequently necessary to transfer it carefully with the water contained in the flask. By heating it to redness, in the way described, its volume is reduced to about one-third its original size ; it at the same time assumes a metallic lustre, and acquires a degree of cohesion which admits of its being readily handled without fear of loss. The return is made to the Mint in decimals, the assayer’s weights being so subdivided as to give him the value in thousandths of the original half gramme. The Bank return is made to the one-eighth of a carat grain “better” or “worse” than standard, and tables are employed for the conversion of assays expressed in decimals, and conversely. The quantity of lead necessary for passing an alloy of gold on the cupel depends on the amount of vopper present. The following pro- portions have, after numerous experiments, been adopted at the Paris Mint. —- Amount of Gold Amount of Lead necessary in Copper Alloy. to remove the Copper by Oupellation. 1000 1 part eas Ele Met rgict oo ab 10 parts ee eed ere teeny EL By os. POON seen. a ie ee ere as. plea Me Oe ae a ae aa gem Ie 500 oO .. ithe Us oe, en ae ee ee a4 2 5. = 5.4 oy ia ge ee ea Stree. ae) BN er Ae hoe Geeky) te j4 ,, LE! MAI Ve Sen OME, Pe | For the assay of ordinary bar gold from California, Australia, or New Zealand, &c., in which the proportion of copper is always ex- ceedingly small, the gold is passed to the cupel, with the necessary amount of silver and two grammes only of lead. But even when the operation of parting has been skilfully conducted, the weight of the cornet of gold will often be increased by a very slight sur- charge occasioned by its retaining minute traces of silver. This surcharge is most observable in cornets obtained from alloys containing a very small proportion of copper ; since, in cases in which large quantities of this metal are present, and a considerable amount of lead has consequently been employed for cupellation, it is more R P42 GOLD. than compensated for, by the loss of gold absorbed by the eupel. In the assay of alloys having an intermediate composition, the loss of cold is not unfrequently counterbalanced by the surcharge of silver, and the true fineness of the alloy thus directly obtained. - - The following results of numerous synthetical experiments made in the Paris Mint, furnish the necessary data for the calculation of a table of corrections :— Fineness of Gold. ; Result obtained. Differences. 900°: boa Ae aS a Se ee ee SOO = “aa Sak BAe eo BO On Fait etre een ae FOO Se ee ee Ol vee re en B00 Sh. PSAs SOO OOS = eae BOG: eG ee seek! ABO] 3 Se eee ADO, 2 Ratha} 3 eS DOR. = eas meee eee 300 “PP a O50 TS Se eee BOO. event tke ee LI OU ee ee one a ea AO CRATE. ee ana ne DODO OF: te ae ee The above experiments were made on mixtures of fine cold. and pure copper, in the proportions indicated in the table. The last traces of silver may be removed from the cornet by treat- ing it, before annealing, with fused bisulphate of potash in a porcelain crucible. When sufficiently cool, the whole is heated with water containing a little sulphuric acid, and the cornet dried and ignited. By this means gold of almost absolute purity may be obtained. The arrangement of Mr. Claudet’s laboratory, Coleman Street, London, which is probably one of the most complete for the assay of gold and silver bullion, is represented Fig. 38. The cupellations are performed in two French cupel furnaces, made of fireclay, bound with flat iron bands, and standing in an arched recess in the wall of the laboratory, before which is an iron screen (divided in the drawing for the purpose of showing furnace) in order to prevent radiation. Slides in this screen can be raised or lowered at pleasure, and are provided with counterpoises similar to the sash weights of a window. The tongs for handling the cupels, with its pasteboard guard to protect the hands of the operator from the heat, are seen between the furnaces, whilst a side view i8 obtained of another similar pair lying on the bench beneath. Under this is kept the coke to be employed as fuel, and to the left of the furnace, lying against the wall, is the paste- board shield, with a piece of green or blue glass in it, used by the assayer to protect his eyes from injury whilst looking into the ASSAY OF GOLD BULLION. 24: Fig. 38. = A iillllll —— WH i ——s =PATAAT A PAY, YYS PIII 2 ae Be AssAyY LABORATORY. 244 GOLD. muffle. The racks in the upper left-hand comer are for the storage of cupels, which, after being made in a screw press, are laid aside in shallow iron trays until nearly dry, when they are removed, together with the trays, to the racks seen, behind the tongs, on the shelf below the furnaces, where the last traces of moisture become expelled. On either side of the furnaces are ranges of flasks for the attack of the inquartated gold, each of which rests on the top of a small button- shaped piece of metal, which has around its edge, apertures for the issue of gas jets. Each of these burners is provided with a separate tap ; and a large stopcock, seen at the end of each series, is used to turn on, or cut off, the supply. A guard with holes in it, corresponding to the different burners, keeps the flasks in their respective places, whilst their open ends are inserted into holes in the tile work at the back, which communicate with the chimney and carry off the gases gene- rated, The vessels resembling teapots are employed for pouring acid into the parting flasks. This gas apparatus, which was first employed by Mr. F. Claudet, is now adopted by most of the principal assayers, both in this country and on the continent of Europe, and has, among other simiar esta- blishments, been introduced into the French Mint. In estimating the fineness of gold, it is sometimes usual to regard the whole mass as weighing 24 carats ; and thus when gold is said to be 18 carats fine, it means that if the whole weight be represented by 24, the proportion of gold will be 18, or that the weight of gold is 18ths of the whole. Touchstone.—In order to ascertain the fineness of articles of jewel- lery, and of other small objects from which a sufficient amount cannot be scraped off for the purpose of an ordinary assay, trial by touchstone is sometimes employed. This is a method of ascertaining the approximate value of an alloy of gold with other metals by ecom- paring the colour, &c. of a minute portion of the object to be exa- mined with small bars of similar alloys, of which the proportional composition has been previously determined. These bars are called touch needles, and are rubbed on a smooth piece of black basalt or slate, called a touchstone. Sets of touch needles may consist of pure gold; of gold of 234 carats ; of 23 carat gold; and thus down to 20 carats, after which the difference between each needle may be a whole carat. ASSAY OF GOLD BULLION. 245 The marks made respectively by the several needles and the object to be tested, are afterwards wetted with a little aquafortis, and, from the effects produced, the composition of the alloy is inferred; since its fineness is supposed to correspond with that of the bar, which affords a trace on the stone similarly affected by the action of acids. In some countries where trinkets are required to be assayed in this way, a great variety of needles is necessary; but in England the touchstone is very little employed, although it can sometimes be used with advantage to indicate the quantity of silver necessary for in- quartation. The British standard for gold coin is 22 carats, and the alloy employed consequently contains 916°66 parts of gold in a thousand. The standard employed in France and America for the gold currency is 900 thousandths. shed Bac Goan ed SD — ——_ CHAPTER XII. MODE OF OCCURRENCE AND GEOLOGICAL POSITION. NATIVE SILVER—ANTIMONIAL SILVER—NATIVE AMALGAM—PRINCIPAL SILVER ORES — SULPHIDES — ARSENIDES — SELENIDES—TELLURIDES—CHLORIDE—IODIDE— BROMIDE — CARBONATE— SILICATE—CHIEF SOURCES OF SILVER — GEOLOGICAL POSITION. MopE oF OccCURRENCE.—This metal occurs in the following forms of combination :— NATIVE METAL AND ALLOYS. Native Silver—This metal sometimes occurs in a state of almost chemical purity, but it is more frequently associated witb copper, gold, bismuth, antimony, or some other metal or metals. Native silver is often found in connexion with various argentiferous ores, and has sometimes been met with in masses of considerable size. The most remarkable of these have been obtained from the mines of Freiberg in Saxony, Kongsberg in Norway, and those of Huantaya in Southern Peru, from which a specimen weighing over eight ewt. was once procured. A mass of native silver from Kongsberg, in the Royal collection at Copenhagen, weighs about five ewt. It is found both crystallised and in arborescent and filiform shapes. The filiform varieties are often composed of one or more series of octahedrons, closely united, or arranged in parallel rows ; this structure is apparent in many of the specimens from Norway ane Mexico. | ae ‘The alloys of silver and gold are exceedingly numerous, ‘and athouse native gold has never been found free from -silver, it is in some cases 248 SILVER. alloyed with that metal to such an extent, that the resulting compound can only be regarded as native silver containing traces of gold. Silver obtained from the treatment of ordinary argentiferous ores frequently contains gold, but generally speaking in small quantities only. In some districts, however, as at Virginia City in the State of Nevada, one-third of the value of the bullion ees arises from the amount of gold which it contains. Antimonial Silver,—Discrasite occurs in veins at Altwolfach in Baden, Wittichen in Suabia, Andreasberg in the Hartz, near Coquimbo, Chili, and elsewhere. Colour, silver white; composition, antimony 23, silver 77 per cent.; formula, Ag? Sb. Heated before the blowpipe, gives off fumes of amen. This substance does not occur in sufficient quantities to possess any great commercial value. Bismuth Silver—A rare alloy of silver and bismuth, with a little copper and arsenic; occurs in the mine of San Antonio, near Copiapo, Chili. It contains 60 per cent. of silver. AMALGAM. Native Amalgam.—-Is found in the Palatinate, at Sala in Sweden, Almaden in Spain, and in various mines in Chili, &c. It is frequently crystallised, of a silver white colour, is brittle, and emits a grating sound when cut. There are two known varieties: the one is repre- sented by the formula Ag Hg’, and the other by Ag Hg*. The first is composed of silver 34°8, mercury 65:2, and the second of silver 26°25, mercury 73°75 per cent. A silver amalgam of some commercial importance is found in the mines of Arqueros in Chili, and has been hence named Arquerite. According to Domeyko, its composition is represented by the formula Ag® Hg; it consists of silver 86°49, mercury 13°51 per cent. ORES. The ores of silver which occur in greatest abundance, and which are consequently the most important, are the following :— Silver Glance-—Vitreous Sulphide of Silver—This is the most im- portant ore of silver, and contains, when pure, silver 87:04, sulphur 12:96 per cent. Its formula is Ag.S. It is found in Europe in the mines of Annaberg and Joachimstahl, and other mines of the Erzge- birge ; at Schemnitz and Kremnitz in Hungary, and at Freiberg. It is MODE OF OCCURRENCE. 249 abundant in the mines of Peru and Mexico, and also in those of the State of Nevada. Stephanite.—Brittle sulphide of silver is the ore of next greatest importance. This is a double sulphide of silver and antimony, con- taining, when pure, silver 70°4, antimony 140, and sulphur 15°6 per cent. Its formula is Ag Se 4 Sb? S* It is found in nearly all the silver mines of Europe, and occurs abundantly in Mexico, Peru, and in the Comstock lode, State of Nevada; beautifully crystallised specimens have been frequently obtained from the California mine worked on that vein. Pyrargyrite.—Ruby Silver.—An important ore in the Mexican mines, as well as of those in the Reese River district in Nevada. It is com- posed of the same substances as Stephanite, but in different proportions. When pure, its composition is, silver 58:98, antimony 23°46, and sulphur 17:56 per cent. Its formula is Ag S+4 Sb? S®. Chloride of Silver—Horn Silver—This ore is composed of silver 75°33, chlorine 24°67 per cent., and is represented by the formula Ag Cl. This substance is found in most of the silver mines both of Europe and America, and occurs in greatest abundance near the out- crops of the veins. It fuses in the flame of a candle, giving off acrid fumes ; and if moistened and rubbed with a piece of iron or zinc, be- comes externally coated with a thin film of metallic silver. With a little carbonate of soda it is readily reduced before the blowpipe, and affords a button of silver. In addition to the foregoing, which yield the larger proportion of the total amount of silver annually produced, there are numerous other minerals containing this metal, but which, from their rarity, may be regarded rather in the light of mineralogical curiosities than as ores of silver. A large amount of silver is likewise extracted from galena, with which it is associated in the form of sulphide. The following is nearly a complete list of the minerals formed by the combination of silver with other bodies :— SULPHIDES, ARSENIDES, SELENIDES, AND TELLURIDES, . Silver Glance.—Sulphide of silver. . Diserasite.—Antimonial silver. . Nawmannite.—Selenide of silver ; occurs in the Hartz. . Stromeyerite.—Sulphide of copper and silver, . Eucairite.—Selenide of copper and silver ; found in Sweden. . Sternberqite.—Sulphide of silver and iron, flexible, and marks like plumbago ; found in Bohemia and Saxony. QD oP CdD 250 SILVER. 7. Hesstte.—Telluride of silver ; found in Siberia. 8, Miargyrite.—A rare sulphide of silver and antimony. 9. Pyrargyrite—Ruby silver. 10, Proustite.—Light red silver ore, composed of sulphur, arsenic, and silver ; found in Bohemia, Saxony, &c. 11. Polybasite.—A variable combination of silver, copper, antimony, arsenic sulphur, and iron ; chiefly found in the Mexican Mines. 12. Frevslebenrte.—Antimonial sulphide of lead and silver ; containing twenty- two per cent. of the latter metal. 13, Stephaniée.—Sulphide of silver and antimony. 14. Xanthocone.—Sulphide and. arsenide of silver; occurs at the Himmelsfiirst Mine in Saxony, and various other localities. CHLORIDE, IODIDE, AND BROMIDE. 15. Horn Sulver—Chloride of silver. 16. Lodyrite.—lodide of silver ; found in Mexico, Chili, and at the Mines of Hiendehveneihs, 4 in the province of Guadalajara, Spain. 17. Bromyrite.—Bromide of silver ; occurs in Chili, Mexico, and at Huelgoét in Brittany. 18. Embolite.—Chlorobromide of silver ; found in Chili, Mexico, and in the State of Honduras. CARBONATS. 19. Selbite.—Regarded as a carbonate of silver, but probably only a i mixture, SILICATE. 20... .. This combination is stated by Mr. J. Napier, Jun. to exist in the ores of the district of Reyes, Mexico.* Few metals enter into a greater variety of natural combinations, or are found over a wider geological range than silver. It is said to exist in minute traces in some organic bodies, and in the waters of the ocean. A certain amount of this metal invariably accompanies native gold, and it would be almost as difficult to find a specimen of galena from which traces of silver could not be extracted, as to meet with native gold entirely free from it, The whole of the silver of commerce is derived from the three following sources :— Ist. From silver ores proper, in which this metal predominates in value over those with which it is associated. 2nd. From refining the native alloys of gold and silver. srd. From the desilverising of lead, and the Weatment of certain ar Ae vee: ores, “ Mining and Sinclting Magazine, ae Ep. 105, GEOLOGICAL POSITION. 251 We shall at present chiefly confine our attention to a description of the principal localities producing ores belonging to the first class, since the second source of silver has been already treated of in the portion of this volume devoted to gold, and the third will receive some attention in subsequent chapters. The principal mining districts in Europe which have been exten- sively worked for ores of this description, are those of Saxony and Bohemia, some localities in Hungary and Transylvania, the neigh- pourhood of Kongsberg in Norway, and that of Hiendelaencina in Spain. On the continent of America, Mexico, and the Cordilleras of Southern America, furnish examples of the occurrence of vast deposits of these ores; whilst more recently the discovery of the Great Comstock and some other veins in the new State of Nevada, has been followed by the production of an amount of silver almost without parallel in modern history. GEOLOGICAL Position oF Sinver.—As before remarked, the rocks enclosing deposits of ores of this class differ widely with regard to their geological age. They occur in true veins in the older crystalline and metamorphic rocks, and when so situated have often been worked to great depths without any apparent change of character or diminu- tion of produce. The mines of Kongsberg in Norway and Freiberg in Saxony, are remarkable examples of this mode of occurrence. In South America, on the contrary, a great portion of the silver ores are found forming veins in calcareous rocks, and often running parallel to their stratification. The age of the silver-bearing rocks of Bolivia and Peru is apparently carboniferous, whilst in Chili the strata in which the ores of silver are most abundant are believed to belong to the cretaceous period.” * Mr. Rémond has obtained fossils in sufficient numbers from the rocks in which are situated the famous silver mines of Chafiarcillo and Tres Puntas, to fix their age as belonging to the Lower Cretaceous.—Proceedings of the California Academy of Natural Sciences, December 3rd, 1866. CHAPTER XIII. PRINCIPAL SILVER MINES OF THE OLD WORLD. SILVER MINES OF THE UNITED KINGDOM— NORWAY—SWEDEN—TRANSYLVANIA AND THE BANAT—SAXONY AND BOHEMIA—MINES OF THE HARTZ—SILVER MINES OF THE ALPS—-FRANCE—SPAIN—ALTAI MOUNTAINS—DAOURIA. SILVER mines were extensively worked in Europe long before the dis- covery of the richer veins of America, and some of them still continue in operation, affording considerable annual returns of this metal. GREAT Britany AND IRELAND.—The whole of the silver produced in the United Kingdom is extracted from argentiferous lead, and consequently an account of the different districts from which it is obtained, would involve a description of the principal lead mines of the country. It may, however, be remarked that the ores obtained from the North of England, generally speaking, contain but a small proportion of silver, usually not above 14 oz. per ton. ‘The ores of the Isle of Man are highly argentiferous, yielding from 50 to 60 oz. of silver per ton of lead, whilst the ores of Cardiganshire and Montgomeryshire are moderately so, containing, on an average, from 15 to 25 oz. of that metal per ton of lead. The lead ores of Denbighshire usually contain a very small amount of silver. Those of Cornwall and Devon are generally richer in silver than any others in the United Kingdom, with the exception of those from the Isle of Man. The Cornish ores contain on an average about 30 oz. of silver per ton. The produce of silver, separated from lead ore, raised from mines in the United Kingdom, from the year 1856 to 1865, both inclusive, has been, according to Mr. R. Hunt, F.R.S., as follows :— Ounces. Ounces. 1856. - 3 614,188 | 1861) i. 27 5GO 580 1 O50. Fema ss OOo COG LS6255 ee 9, eee tes WSoe es 8. 669,345 18635. Se £634,004 PSD a Cy ss LOT COLT 1864 7, we Ot Lae ESB0° aS DOL OO? 1805), 8 PPA SG PRINCIPAL SILVER MINES OF THE OLD WORLD. 259 Norway.—The celebrated mines of Kongsberg were discovered in 1623, and have been worked, with but comparatively little interruption, from that time up to the present. On the separation of Norway from Denmark in 1814, the present Government took the mines of the territory of Kongsberg into its own hands, and appointed a Com- mission for the purpose of deciding which of them should be re-opened. In addition to the Gottes Hiilfe their choice fell on the Kongens and Armens mines, but, at a depth of forty fathoms from the surface, the former became so impoverished that it was abandoned, and the working of the Armens alone for some time proceeded with. At the depth of sixty fathoms the condition of the Armens mine was considered so satisfactory that it was thought advisable to extend a level from it into the adjoining mine. This operation resulted in making important discoveries, and the two properties have been since worked as one establishment. During the early part of the eighteenth century the mires of Kongsberg were remarkably productive, but from the middle of that century up to 1832 their yield was comparatively insignificant. Since that time they have been regularly worked with uniform and satisfactory results, and have now reached the depth of 280 fathoms from the surface. ‘These mines are situated in gneiss and crystalline slate, of which the district for a length of a hundred miles and a breadth of fifty, 1s chiefly composed. The silver occurs in what are called Fahlbands, which consist of parallel belts of rock, of considerable length and breadth, impregnated with sulphides of iron, copper, and zinc, and sometimes also with those of lead, cobalt, and silver. The iron pyrites is often more or less decomposed, giving rise to the formation of hydrated oxide of iron, the presence of which is considered in the district an indication of silver. The direction of the ore-bearing belts is nearly north and south; they are irregular in their dimensions, but constantly preserve a certain degree of parallelism with each other, and may be traced for an extent of several miles. The amount of ore disseminated through them is usually small, but in some places it is sufficiently concentrated to admit of being profitably worked. In the Kongsberg district, there are several of these fahlbands, parallel in strike and inclination with the gneissoid and schistose strata in which they occur, and subject to the same local.structure and disturbances ot stratification. The fahlbands are themselves traversed by true veins containing silver ores, and experience has shown that these are never 254 ‘ SILVER = argentiferous except where they intersect the fahlbands. From this it would appear that the impregnation of the veins is dependent on the nature of the enclosing rock, which renders it probable that their metalliferous constituents were originally derived from the fahlbands, from which their removal and subsequent concentration have been effected by chemical action. The total produce of silver from the Kongsberg mines from 1624 to 1864,—240 years,—has been, according to official returns, as follows V1Z. -— From 1624 to 1805 . . . 2,360,140 marks,* equal to 1,332,495 Ibs. troy 27] BOS te RENGs Boe SE 38419 ~ i OL eT ee ge UB1Br 5) 4864. 2.2. 99820056) uy 463;498 45° ies The average annual produce has been— From 1815 to 1883 . . . 4,141, marks, equal to 2,338 Ibs. troy see glupaeney ees 27,493, 5 15,483 oun Pe oO ETN oe eee eee 25,454 _,, ee 14, 36]eg, ore PAE Bec ORS UY seamen 23,464 _,, Z 13,247 ,, ,, i ROAD 550 Mae. ane ies 20,552 ,, i. 11,6035 so 5 LSD E OOO awe 32,862 ,, is 18.653: .-— 5 jy ASOD RS BCS ats 85 16,092 — ,; i$ 9,084 7453 From 1859 to 1864 the annual yield has been— LO ater taarh yea Taek ae 20,515 marks, equal to 11,582 Ibs. troy TOC ns OE See Oana ay x: 10,241 "ee LROW Reon, SUNSETS oe eRe 3 8,369" 7s TEGO A eee hoa tiaeeee 13,088 ,, : 4,309 24a LEC ie ie et I Boa . 7,842 420 ST igre a isan aie) a Teh a 7,305. ae In addition to the mines of Kongsberg, some veins in the district of Skara were formerly of considerable importance, but are now abandoned, although the fahlbands of this locality closely resemble those which have proved so productive in the adjoining district. The produce, expenses, and net profits of the Kongsberg mines, during the last thirty-one years, have been as follows :— * The mark of Norway and Sweden is equivalent to 3,252 gr., or 6°775 oz. troy. PRINCIPAL SILVER MINES OF THE OLD WORLD. STATISTICS OF THE KONGSBERG MINES. | YEAR. 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 | 1849 | 185) 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 Averages. | | PRODUCE SOLD, EXPENSES. Net PRorit. £87,558 | £17,407 | £70,151 Seige a) 8 16,85 et ea 70,244 13,585 | 56,659 62,087 |} 21,015 =| = 31,072 58,137 | 21,258 | 36,879 f 69,879 | 20,110. | 49,769 f 64,236 20,497 | 43,739 4 50,009 22,030 27,979 \ 49.915. 4 19,594 | -. 23,391 41,398 - | 19,811 . | -. 21,587 Ce ae ames Wi 21,345 36,772 | 16,462, 20,310 37,297 12,642 24,655 51,831 | 19,146 32,685 75,788 16,268 59,520 49,934 18,621 31,313 47,518 16,362 31,156 38,140 15,975 22.165. 40,770 16,905 23,865 36,363 16,444 | - 19,919 51,616 17.964..-"745, 23,622 82,448 20,294 62,154 66,922 19,613 47,309 49,627 17,886 31,741 84,356 20,136 64,220 41,888 20,996 20,892 37,157 23,420 13,737 30,141 24,037 | 6,104 26,708 20,551 | 6,157 28,836 20,982 7,854 28,090 OMTTLE| a 6,919 £50,750 £18,885 | £31,704 bo Ot Ou 256 SILVER. SwuEpEN.—The silver mines of Sweden were formerly of con- siderable value, but aré at present less productive. Three mines of this metal were working in 1767, viz.: that of Hellefors in the Province of Wermland, that. of Segersfors in Nericia, and that of Sala in Westmannia, the last being the only one of any importance. It is very ancient, and is said at one time to have yielded large quantities of silver, but its present annual produce is only from 2,258 to 2,823 lbs. troy. The ore is a highly argentiferous galena. Huncary, TRANSYLVANIA, AND THE Banat.—The mines of this region may be divided into four principal groups. The Schemnitz district comprehends the mines of Schemnitz, Kremnitz, Neusohl, and Schmdlnitz. Schemnitz.—Schemnitz, a royal free city of mines, 1s situated twenty-five leagues to the north of Buda, at a height of 1680 feet above the level of the sea, in the midst of a group of mountains covered with forest. These mountains are for the most part composed of trachytes, enclosing a formation consisting of porphyry associated with syenite, passing into granite and gneiss, with subordinate beds of slate and limestone. All the mines occur in this formation. Beudant, who compared these rocks with specimens of the metalli- ferous porphyry, &c., brought from South America by Humboldt, long since recognised their exact identity, not only in the most minute details of colour, structure, and composition, but also in the respec- tive positions of the different varieties, and the same similarity of the enclosing rocks would seem to exist with regard to the recently- discovered silver districts in North America. The metalliferous rocks of Schemnitz occupy a tract of some miles in extent, and are traversed by a group consisting of five principal veins running north-east and south-west, in addition to which there are numerous others of less importance on the north side of the Paradise mountain. The largest of these, the “ Spitaler gangue,” has occasionally a width of sixty feet, and may be traced for upwards of four miles in length. These lodes have seldom any distinct walls, but the enclosing porphyry is frequently more or less decomposed and impregnated with iron pyrites in the vicinity of the planes of contact. The veins are rarely subject to interruption or dislocation by slides or cross-courses.' The veinstone consists of fragments of the enclosing rocks (which are often decomposed to the consistency of clay), cavernous quartz, ferruginous limestone, and sulphate of baryta, PRINCIPAL SILVER MINES OF THE OLD WORLD. 257 with which are associated blende, iron and copper pyrites, argen- tiferous galena, sulphide of silver, ruby silver, and metallic silver, in addition to a small quantity of gold which is rarely visible. Sulphide of silver and argentiferous galena are the two most important minerals, and sometimes occur in distinct patches, whilst at others they are intimately mixed and disseminated throughout the gangue. The gold and silver are usually found to accompany each other, but they do not now occur in such large quantities as formerly, since the proportion of galena present in the veins evidently increases in depth. The argentiferous ores from Schemnitz are smelted near the mines, the resulting work lead being sent to refining establishments at Krem- nitz, Neusohl, and Scharnowitz, where the silver ores obtained from the other mines in the neighbourhood are also treated. The mines of Schemnitz were first opened more than eight hundred years ago, and have been worked to a depth of over two hundred fathoms ; the works have been generally conducted with great care and skill, but from the falling off of the produce of the ores, they are not now in So prosperous a condition as they were a century or more since. The Empress Maria Theresa founded a School of Mines at Schemnitz in 1760, which was for many years celebrated throughout Europe, but since the year 1848 the number of students has con- siderably declined, and the rival schools of Przibram and Gratz have proportionately increased in importance. ) Kremnitz is situated about five leagues north-west of Schemnitz, in a valley bounded on the right by a range of hills composed of rocks similar in their character to those constituting the metalliferous formation in the vicinity of the latter town. Enclosed in these rocks are veins closely analogous to those of Schemnitz, except that the gangue contains a larger proportion of quartz, and that the ores are generally more uniformly auriferous. The metalliferous area is here of very moderate extent, and is surrounded by a trachytic formation, which geologically belongs to a more recent epoch, Kremnitz is one of the most ancient royal free cities of mines in Hungary, and has a mint where all the bullion obtained is sent to be parted and refined. Neusohl lies about six leagues north-east from Schemnitz, on the banks of the river Gran, and was originally founded by a colony of Saxon miners. The mines are here situated in grauwacke, covered by limestone, and afford argentiferous copper ores. They have been s 258 SILVER. worked since the thirteenth century, and annually produce about 105 tons of copper and 1,053 Ibs. troy of silver. The mines of Lower Hungary afford employment to 15,000 work- men, and yield metals of the total annual value of 360,000/. In the neighbourhood of Schmélnitz are copper and other mines belonging to private individuals, which produce, in addition, a certain amount of silver and mercury. They are chiefly worked by a Com- pany called the Waldbiirgerschaft, which produces annually 850 tons of copper, 3,535 Ibs. troy of silver, and about a hundred flasks of mercury. Nagybanya.—tThe veins of this group lie in a chain of mountains which, proceeding from the frontiers of Buckowina, where it unites with the Carpathians, finally disappears among the sandstones on the northern frontier of Transylvania. This district produces some gold, but its annual yield of silver is small. Abrudbanya.—Nearly all the mines of this district occur in the mountains which rise in the western part of Transylvania, between the Lapos and Maros, in the vicinity of Abrudbanya. The most productive veins are principally found in porphyries analogous to those of Schemnitz, although some of them are enclosed in mica slate grauwacke, and limestone. The principal veins are those of Nagyag, Kérésbanya, Offenbanya, Vo6réspatak, Boitza, Csertesch, Fatzbay, Fiizes, Vulkoj, Porkura, Butschum, and Toplitza. The mines of all these localities produce gold, together with a certain amount of silver, which is smelted at the works at Zalathna. They are celebrated for producing ores of tellurium. Banat of Temeswar.—The mines of the Banat chiefly occur in the mountains that enclose the valley of the Danube at Orsova, through a narrow gorge in which the river finds a passage. The most important mines of this district are those of Oravitza, Moldawa, Szaszka, and Dognaczka. They principally afford argentiferous copper ores, yielding about 120 oz. of silver to the ton, together with a little gold. These ores are obtained from veins and deposits chiefly occurring between the mica slate and limestone, or between syenite and limestone. Well defined veins are also found enclosed in syenite and mica slate. The mines of Hungary, Transylvania, and the Banat, produce about 92,000 lbs. troy of silver annually. Saxony AND BonemMiA.—The chain of the Erzgebirge, which, on | the western bank of the Elbe, separates Saxony from Bohemia, has for PRINCIPAL SILVER MINES OF THE OLD WORLD. 259 many centuries produced a certain annual amount of silver. The silver mines of this district have been opened on veins which are, for the most part, enclosed in gneissoid rocks ; their thickness rarely exceeds a few feet, and they are associated in groups, whose relative importance has varied considerably at different periods. Mining operations are said to have been first commenced in this district as far back as the beginning of the tenth century, but there are no authentic records on this subject dating prior ‘to about the close of the twelfth, when the still productive mines of Freiberg began to be worked. The mines of Saxony suffered severely from the effects of the Thirty Years’ War, during which, many considerable mining towns were entirely destroyed, and some of them have never recovered their former importance and prosperity. Freiberg, Marienberg, Annaberg, Schneeberg, Johann-Georgenstadt, and Schwarzenberg in Saxony, and Joachimsthal in Bohemia, have at various periods been the chief local centres of this mining region. More than nine hundred different veins are said to exist in the Erzgebirge district, which, in accordance with the nature of their gangues, have been divided by Von Weis- senbach into the four following classes : *— 1. Quartz veins, containing iron pyrites, mispickel, blende, and galena; and affording silver ores of a moderate percentage. 2. Brown spar veins, yielding the same ores as the preceding, but richer in silver. 3. Veins of which the gangues are composed of carbonate and oxide of iron, fluor spar, and sulphate of baryta; but not so metal- liferous as the two preceding. These sometimes extend into the Zechstein formation. 4, Veins with calcareous gangues, occasionally affording rich ores. The characteristics of the different classes of veins do not, however, appear to be so marked as to admit of their being divided into any definite number of well-defined systems. Lreiberg.—The Freiberg mines afford an interesting example of silver veins retaining their character and richness at considerable depths. Many of the mines now exceed 230 fathoms in depth, and notwithstanding the increasing expenditure incident to this cireum- stance, their prosperity has continued to be constantly progressive. The most celebrated and productive of the Freiberg mines during the present century, have been those of Himmelsfiirst, Himmelfahrt, and Beschertgliick; and with a view to facilitate their drainage, it has been * Annales des Mines, 8, 4, t. xi. p. 27. s 2 260 SILVER. proposed to bring up a deep adit from the valley of the Elbe, a distance of about eighteen miles. The ores of the Freiberg mines consist of the various sulphides, particularly vitreous silver, pyrargyrite, light red silver ore, stephanite, freislebenite, and native silver. The latter sometimes occurs in large masses, and the veins occasionally yield considerable amounts of argentiferous galena. The total yield of silver from the mines of Freiberg from 1524 to the end of 1850, was 5,613,228 lbs. troy. As a general rule, the productiveness of these mines has, subject to tem- porary fluctuations, increased with their progressive depths. At the time of the publication of the work of Heron de Villefosse, “ Sur la Richesse Minérale” (1819), the Himmelsfiirst was the most productive mine, but since 1830 its yield has declined, and the Himmelfahrt has occupied the first position, having afforded, from that time up to 180, 146,869 lbs. troy of silver. Marienberg.—Formerly the mines of Marienberg, a small town twenty-five miles south-west of Freiberg, were exceedingly flourish- ing, and in the sixteenth century ores were frequently found there producing 85 per cent. of silver. The troubles attending the Thirty Years’ War put an end, however, to their prosperity : since that period they have never exhibited any degree of activity, and their annual returns are now very inconsiderable. Annaberg—tThe production of the Annaberg district during one hundred and ninety-one years, from 1654 to 1845, amounted in value to about 850,000. but the yield of the veins has decreased in depth, and their annual returns are now exceedingly small. Schneeberg.—The Saint-George mines, near Schneeberg, were opened in the fifteenth century, in search of ironstone, but soon became celebrated for their large production of silver. Towards the close of that century a mass of ore was discovered in them which afforded nearly twenty tons of that metal; but after this period they became rapidly impoverished as silver mines, but have been worked during the last two hundred years for ores of cobalt, for which they are celebrated, and which are found in the veins formerly yielding such large quantities of silver. Mining operations at Schneeberg are now carried on only on an exceedingly Jinted scale. J ohann-Georgenstadt.—There are several small mines in the neigh bourhood of this town, producing a little silver, but the aggregate amount is exceedingly small. The veins in this district yield a certain amount of bismuth and uranium, and some of them are PRINCIPAL SILVER MINES OF THE OLD WORLD. 265 worked for the ores of these metals. The mines of Schwarzenberg are no longer of any importance. The average richness of the silver ores throughout Saxony is from sixty to seventy ounces per ton, and the annual production of the country about 80,000 lbs. troy, of which the mines of Freiberg alone yield about ninety-seven per cent. Joachimsthal—These mines, which are of great antiquity, and were formerly of much importance, have been worked to a depth of 325 fathoms, but their produce has for many years been gradually declining in amount, and their annual yield is at present insignificant. MINES OF THE HAntz.—The most productive silver mines of the Hartz are those in the neighbourhood of Andreasberg, of which the most extensive are the Samson and Neufang mines, which are worked to a depth of 430 English fathoms. They were discovered in 1520, and produce argentiferous galena, in addition to silver ores properly so called. The district yielding the largest amount of argentiferous galena is that of Clausthal, which comprehends several mines worked at a depth of above 300 fathoms. The most extensive of these are the Dorothea and Carolina, the latter of which furnishes a large proportion of the annual produce of the district. The grant of the Dorothea mine extends over a length of 257 yards on the run of the vein, with a moderate width at right angles to its direction. Within this small area there were extracted, from 1700 to 1807 inclusively, 553,200 Ibs. troy of silver, besides 38,441 tons of lead, and 1,192 tons of copper. The profits realised from this mine, together with that of Carolina, during the same period, amounted to 1,120,0002., besides which the shareholders contributed largely, by means of loans without interest, to carry on the exploration of various less productive mines in the district. The annual production of silver from the Hartz mines is about 27,040 lbs. troy. MINES oF THE ALPs.—The mine of La Gardette in the Oisans, Department of the Isére, was worked during the latter portion of the eighteenth century, on a quartz vein containing small quantities of gold and silver, but it never paid the expenses of extraction, and has long since been abandoned. The mine of Chalanches or Allemont, in the same Department, was regularly worked from 1768 to 1815, but is now also abandoned. The ore consists of various minerals, containing 262 SILVER. silver, disseminated in a clay which fills the fissures and irregular cavities in taleose and hornblendie rocks. This mine yielded annually, towards the close of the last century, 1,252 Ibs. troy. The mines of Kitzbiithel and Réhrerbiichel in the Tyrol were formerly worked on a considerable scale, and in the middle of the eighteenth century were considered among the deepest in Europe, but were shortly afterwards abandoned. They produced copper pyrites, and argentiferous fahlerz, occurring in a elay slate. The ores from these mines, together with the products from some smaller workings in the neighbourhood, were smelted at the works of Brixlegg, near Schwatz. The produce of the mines of the Tyrol, towards the middle of the last century, amounted annually to 6,296 Ibs. troy, and was before that time considerably greater, but has since de- clined in importance. There are mines of argentiferous copper ore at Schladming, Feistritz, Walchern, and Kallwang, but their annual product of silver is unimportant. The mines of l Argentiére, Hautes Alpes, were probably worked by the Romans, but are known to have been in active operation in the twelfth century. The ores contain about 50 per cent. lead, and 0°0024 of silver. These mines are worked on three veins, of which the largest is 16 feet in width. Although not belonging’ to the above category, it may be mentioned that the mines of Wittichen in the Black Forest produced, some years since, 880 lbs. troy of silver per annum. 7 NORTHERN AND CENTRAL FRANCE, &¢.—Huelgoét in Brittany, although strictly speaking a mine of argentiferous galena, produces an ochreous substance containing about 30 oz. of silver per ton, in the form of chloride, which was until recently extracted by a process of amal- gamation somewhat similar to that formerly employed at Freiberg. The mines of Pontgibaud produce large quantities of argentiferous galena, rich in silver; these are treated by a process of smelting which will be described with considerable detail in a subsequent chapter. In addition to the mines of Pontgibaud, Puy-de-Déme ; of Poullaouen, and Huelgoét in the Department of Finistére; of Vialas in the Lozére ; and of Pontpéan, Department of Ille-et-Vilaine, there are in France various other localities affording argentiferous lead ores; but as these cannot be strictly regarded as ores of silver, a detailed description of them does not come within the limits which we have assigned ourselves. Spain.—The silver mines of Gaudalcanal and Cazalla, to the north of Seville, occur in mica slate, and were formerly highly productive, PRINCIPAL SILVER MINES OF THE OLD WORLD. 263 but are now of little importance; there were also mines at Villa- Guttier, not far from that city, which are said to have furnished 170 marks of silver daily during some portion of the seventeenth century. A silver vein was also formerly worked in the Sierra Almagrera, and was followed to a depth of above a hundred fathoms. The most important silver mines of Spain are, however, those of Hiendelaencina. The mines of this district are situated about 70 miles north of Madrid, in the province of Guadalajara. They were discovered in 1843 by a peasant who had been in Mexico, and who on his return to his native country, remarked the resemblance which a large stone situated by the side of the road, near the village of Hiendelaencina, had to the ores he had assisted to workin the Mexican mines. On examination, by the celebrated chemist Orfila, this stone was found to be an exceedingly rich ore of silver, and preved to be part of a lode which outcropped at that point. Shortly after this discovery a concession was obtained, and the first of the numerous mines of this now widely-known district was commenced under the name of The Santa Cecilia, in honour of the patron saint of the village. Of the other mines which were sub- sequently opened, the most remarkable are the Suerte, Fortuna, Verdad de los Artistas, Relampago, San Carlos, and Vascongada, all of which have yielded immense wealth. There are numerous other lodes in the district, but, up to the present time, that on which these mines are situated has alone been worked with advantage. Its direction is east and west, with an underlie south, and its average thickness scarcely two feet; the enclosing rock is gneiss, accompanied by a coarse talcose slate. The vein is chiefly composed of sulphate of baryta, together with a little quartz; carbonate of iron is, however, often found asso- ciated with them, especially in the richer parts of the lode. Many varieties of silver ores have been found in this district, but by far the most abundant is silver glance; beautiful specimens of ruby silver are also frequently met with. The average yield of the ores produced is about 44 oz. of silver per quintal, or 90 oz. per ton. The greater portion of these ores has been purchased by the Bella Raquel Company, and reduced at their establishments at Constante, about three miles from the mines, to which there is an excellent cart road. A portion of the richest ore was, however, at one time sent to England for treatment, but the whole produce of the mines is now again purchased by the Bella Raquel Company. These mines have declined in their yield since 1858, many of them being at the present 264 SILVER. time far less productive than formerly. The mines of Hiendelaencina have been worked to a depth of about 200 fathoms, and the conces- sions are generally 200 yards in length by 100 yards wide. The production of these mines since 1846, when they were first extensively opened, has been as follows :*— YEAR. FINE SILVER. marks oz. ochs. | Spanish ounces. 1847 4958 1 6 39,665°7 | ) 1848 ; | 17,845 6 4 138,766°5 | | 1849 21,633 6 4 173,070°5 1850 48,516 6 6 388,134°8 1851 68,029 7 2 544,239°3 1852 64,616 4 2 516,932'3 1853 | 69,178 1 5 553,425'6 1854 89,784 3 4 718,275°5 Z 1855 80,359 3 4 642,875°5 F 1856 67,730 2 4 541,842°5 F 1857 65,072 0 0 520,576°0 =) 1858 86,052 1 5 688,417°7 a 1859 67,412 2 4 539,298°5 . E 1860 50,639 6 3 405,118°3 © 1861 40,780 3 5 326,243°6 a 1862 31,745 2 3 | 253,962°4 | | is 1863 24.598 2 3 196,786°4 | | 1864 19,019. 0 3 152,152°4 | 1865 9,362 5 4 74,901°5 1866 June 30, >, 5,226 1 | 41,809°1 6 months | Silver in Ore sent to Eng- | land, as per Assay. . 740,210°2 Total Produce, 194 years. | 8,196,704°3 - Attal Mountains.—The most important silver mine of this district is that of Zméof, situated to the north-west of the high mountains in 51° 9’ N. lat., and 79° 49’ long., east of Paris. It is worked on a vein containing chloride and sulphide of silver, native silver and * Communicated by Messrs. Taylor and Sons. PRINCIPAL SILVER MINES OF THE OLD WORLD. 269 native gold, together with various ores of copper, generally more or less argentiferous. The gangue consists of sulphate of baryta, car- bonate of lime, quartz, and occasionally, fluor spar. The principal vein, which is very large, has been traced for a distance of several hundred fathoms, and is worked to a depth of 95 fathoms. This vein has near the surface a considerable inclination, but becomes nearly verticalin depth. Its roof is of clay slate, but on the foot wall the slate is much mixed with hornstone. It throws out numerous branches, is not unfrequently intersected by cross-courses, and was more productive near the surface than at the present time. The other silver mines of this region are those of Tcherepanofsk, three leagues south-east of Zméof; those of Semenofsk, ten leagues south-east ; those of Nicolaiefsk, twenty leagues to the south-west ; and of Philipofsk, ninety leagues north-east of the same locality. The last mine lies on the extreme frontier of Chinese Tartary. DaourtA.—The name of Daouria is given to the great mountainous tract extending from Lake Baikal to the Eastern Ocean. The metalliferous portions of this district consist of granite, hornblendic shales, and slates, overlaid by a grey limestone, sometimes silicious and argillaceous, in which are veins of argentiferous lead ores. The silver from this district appears to be chiefly, though not entirely, derived from galena, and is estimated to amount to about 21,000 lbs. troy annually. This silver contains a small proportion of gold. Many of the mines of Daouria are reported to be, at the present time, nearly exhausted. CHAPTER XIV. SILVER MINES OF NORTH AMERICA. PRINCIPAL MINING DISTRICTS OF MEXICO—-PRODUCTION OF SILVER IN MEXICO UP To 1845—PRODUCE OF ORES TREATED — GUANAXUATO— ZACATECAS— FRESNILLO —REAL DEL MONTE—HISTORY AND OPERATIONS OF THE REAL DEL MONTE MINING COMPANY—PRINCIPAL MINING DISTRICTS OF NEVADA—COMSTOCK VEIN —pDISCOVERY OF SILVER AT VIRGINIA—YIELD DURING FOUR YEARS—SUTRO TUNNEL— REESE RIVER DISTRICT—SYSTEMS OF VEINS — AMADOR DISTRICT— RAVENSWOOD—CORTEZ—W ASHINGTON—UNION—SMOKY VALLEY-—TWIN RIVER— SAN ANTONIO—OTHER MINING DISTRICTS—TABLE SHOWING NUMBER OF REDUC- TION WORKS, ce. Tue principal silver mines of North America are those of Mexico, although large quantities of this metal have of late years been afforded by the State of Nevada. In addition to Nevada, other portions of the possessions of the United States, and particularly Idaho and Colorado, are known to contain valuable mines of this metal; but they have been, as yet, for the most part, imperfectly explored, and it is ex- tremely difficult to obtain reliable data from these comparatively new and outlying countries. Mexico.—Our information relative to the mines of Mexico is chiefly derived from the works of European authors, who have either visited the country for scientific purposes, or who, for a time, lived there in connexion with some of the different mining and metallurgical enter- prises, which have at various periods been established on that portion of the American Continent by the capitalists of the Old World. By this means, although a large amount of information has been accumu- lated with regard to the quantities of silver obtained from the different districts, and connected with the various processes employed, both for the extraction and reduction of the ores, we are, nevertheless, without such exact geological data as would enable us to become thoroughly acquainted with the characteristics of the mining regions, and the precise nature of the relations and differences existing between the principal metalliferous centres, SILVER MINES OF NORTH AMERICA. 267 The workings have, for the most part, been excavated on true veins ; and deposits in the form of beds or interfoliated masses, running parallel with the stratification of the enclosing rocks, are by no means of frequent occurrence. The veins are chiefly enclosed in what have been designated, by those describing them, as primitive and transi- tion rocks, but of which, a careful and minute examination would doubtless enable the geologist of the present day, not only to determine the relative ages, but also to assign their true position in the geological series. Humboldt calls the limestones of the district of Tasco and Catorce “Alpine” and “Jurassic limestone,” whilst Burkart speaks of them as “ mountain limestone;” from which it may be inferred that at least a portion of them belongs to the carboniferous period. The summits of the highest mountains generally consist of granite, gneiss, and mica slate, but their flanks are in most cases covered by deposits of porphyritic and trappean rocks, through which the granite seldom makes its appearance. The most metalliferous rocks of Mexico are varieties of syenite and porphyry, but Humboldt considers that the determination of their relative geological ages would be an ex- ceedingly difficult problem. They are, however, generally characterised by the presence of hornblende, and the absence of quartz. The veins of this country have generally a direction north of west and south of east, with a considerable dip, which is more frequently towards the south than towards the north, and they generally intersect the enclosing rocks at a very decided angle. The largest vein which has been worked in Mexico is the Veta Madre of Guanaxuato, which is sometimes two hundred feet in width, and which has been opened on at various points over a distance of more than three leagues. In 1845 the workings on this lode had already attained a depth of above three hundred fathoms. The lode next in magnitude is the Veta Grande of Zacatecas, which is sometimes seventy-five feet in width ; although the generality of the argentiferous veins of Mexico do not possess these extraordinary dimensions, but vary in width from a few inches to six or eight feet. The veinstone is generally quartz, and the outcrops or erestones can frequently be traced for long distances on the surface, standing above the level of the enclosing rocks. The ores consist of the various simple and compound sulphides of silver, which have, near the surface, frequently become decomposed, and given rise to the forma- tion of native silver, and various secondary combinations, of which 268 SILVER. the chloride is the most important. The outcrops and shallow portions of the veins are generally drusy, and much stained by oxide of iron ; and from their red colour are called colorados by the Mexicans, cor- responding to the gossans of the Cornish miner. Below the point at which this decomposition has taken place, and consequently where the sulphides remain in their original state, the ores are called negros (black ores), which, according to Duport, afford seven-eighths of the total produce of Mexico. At the date of the publication of Humboldt’s “ Hssai Politique,” the richest mines of Mexico, arranged in accordance with the im- portance of their several yields, followed each other in the annexed order.* Guanaxuato . . Intendancy of Guanaxuato Gatorce . . . Sa 5, san Luis Potosi Zacatecas . . . . 5, Zacatecas Real del Monte . s », Mexico Bolasios he 04% re 5, Guadalajara Guarisamey . . a », Durango Sombrerete . . x », Zacatecas SD AGGO- Gees ake - » Mexico Batopilas << s. ~. Ry », Durango Zimapan .. . es », Mexico Presnillo 62052 24 5 ,, Zacatecas TaMOR sa ay as is = , san Luis Potosi Paral ee es i », Durango The veins of Tasco, Tlalpujahua, Sultepec, Moran, Pachuca, and Real del Monte, as well as those of Sombrerete, Bolanhos, and Batopilas, have, from time to time, afforded immense wealth, but their produce has been generally of a less uniform cha- racter than that of the mines of Guanaxuato, Zacatecas, and Catorce. The silver extracted from the mines of Mexico, from January 1, 1785, to December 31, 1789, is stated by Humboldt to have been as follows :— * With regard to the production of the precious metals, McCulloch remarks : “The silver and gold mines of Mexico have always been deemed the main source of its wealth, and unquestionably its mineral riches far exceed those of any part of America, except perhaps Peru. Before the War of Independence there were in the thirty-seven mining districts of New Spain somewhat more than 3,000 mines, pro- ducing annually about $21,000,000 in silver, and about $2,000,000 in gold.” SILVER MINES OF NORTH AMERICA. 265 Name of Provincial Treasury. c pedaiipals ate ap enriateey by marks. | marks. ii Cea tce 06 ee 950,185 104,835 ENE a 1,031,360 173,631 Guanaxuato .. . 3 1,937,895 531,138 San Luis Potosi . . . 1,491,058 24,465 ROPER EE sg ena) 536,272 386,081 Guadalajara . .. . 405,357 103,655 Balko e . 336,355 27,614 mombprercte’; =. 6" 136,395 184,205 mumapad. we ek ek 1,215 247,002 ACHR ee Met pr 269,536 185,500 Trosario Ae re ey? ot. 477,134 191,368 Lopalae A 7,572,762 2,159,494 The above is equal to a returned production of 9,732,256 marks, or about 6,100,000 lbs. troy. Humboldt, however, estimates that silver to at least one-fifth of the above amount, had not passed through the Government Offices ; and consequently the true produce would thus become 11,678,659 marks, or 7,314,344 Ibs. troy. The mines of Zacatecas were first opened in 1548, and those of Guanaxuato ten years later, about which time the patio process of amalgamation was also introduced. The annual total yield of the Mexican mines at this period has been estimated by Humboldt at from $2,000,000 to $3,000,000, and it subsequently increased, during the eighteenth century, until it finally reached $23,000,000. The production appears to have reached its highest point between 1800 and 1810, when the average coinage of gold and silver at the various mints in Mexico was $23,664,622, the ratio of the former metal to the latter being, by weight, 0:0029:1,; and in value, 0:05:1. During the War of Independence a great falling off took place in the production of the precious metals, which between 1810 and 1845 did not average above $12,000,000, for silver, with a little over $100,000 in gold. Since 1850, however, the mines of Mexico have regained their ancient prosperity, and their present annual produce cannot be much less than $26,000,000 in silver, and $3,200,000 in gold. It is, however, to be regretted that our information with regard to the production of the Mexican mines does not come downto a recent date; since 270 SILVER. no investigations on this subject appear to have been made, by any competent authority, since the appearance, more than twenty years since, of the works of Duport and Chevalier. The latter author estimates the total produce of silver from the Mexican mines from the earliest period up to 1845, at 162,858,700 Ibs. troy. The quantity of silver obtained from the ores by amalgamation was, at the close of the last century, in the proportion of 3°5 :1 of that produced by smelting. This ratio was ascertained from the general table prepared at the provincial treasuries of the different mining districts. In some of the districts, however, as for instance, those of Sombrerete and Zimapan, the produce from smelting was greater than that from amalgamation. In 1846 it was, however, estimated by Mr. J. Phillips, that one-eighth only of the silver produced in Mexico was at that time obtained by smelting.* The result of investigations made some years since, showed that the average richness of all the ores treated from the Mexican mines was from 2 to 3 oz. per quintal, or that the 1,878,400 lbs. troy of silver, produced from the country in prosperous years, were extracted from 446,428 tons of mineral, of which a portion was smelted and the remainder amalgamated. This would give a mean average produce of a little more than 50 oz. per ton. In the district of Pachuca, the ores of the Biscaina vein were, in 1803, divided into three classes. The minerals of the first class con- tained, on an average, about 110 oz. per ton, those of the second 45 02. and the poorest only 30 oz. per ton. In the district of Tasco, the ores of Tehuilotepec afforded, on an average, about 40 oz. of silver per ton. In 1791 the Valenciana mine of Guanaxuato, then in its most flourish- ing condition, yielded ores of different degrees of richness, in nearly the following proportions :— In 1,000 parts. Yield of silver per ton. pte aie SEY ENN) by SPDR ri ene ee ae BE UE eRe WR ee se ore aay Ps ee eo cue rere nen Vier Nh a ee OG tie i ue aces ae re a In the above year the total amount of silver extracted from the mine was 360,000 lbs. troy, of which the ores affording 50 oz. of silver per ton represented 123,508 lbs. Space will not allow us to give even a brief description of all * “ Descriptive Notice of the Silver Mines and Amalgamation Process of Mexico.” By John Phillips. London, 1846. SILVER MINES OF NORTH AMERICA, AAFC F the productive mining regions of Mexico, and we shall consequently confine ourselves to certain details relative to some of the best known and most important districts of that country, at the same time select- ing such as may serve as types of silver mining generally, on this portion of the American continent. About the year 1821, it having become evident to the Mexican Government that the pecuniary resources of the country were not sufficient to admit of the efficient development of its mines, a proposition was made to allow foreigners to participate with the natives in mining undertakings, and thus to allow of the introduction of foreign capital. This proposition was eagerly responded to by European capitalists, and in 1829 seven large English Companies, one German, and two American Companies were in operation. The English Companies were the Real del Monte, the Bolafios, the Tlalpujahua, the Anglo-Mexican, the United Mexican, the Mexican, and the Catoree. Of these the United Mexican and the real del Monte are now alone in operation. Gvanaxuato.—The Veta Madre traverses at the surface a con- _ glomerate possessing many of the characteristics of a red sandstone, and subsequently enters a foliated rock of greenish colour, sometimes talcose, enclosing beds of serpentine, occasionally including syenite and a bluish clay slate. The inclination of the vein is about 45° south- west, and its width is seldom less than thirty feet, but it sometimes increases to two hundred. It is generally divided into three bands, separated by intervening sterile rock. The central band is the widest and most productive, but the upper division has also been much worked, and has produced large quantities of ore, whilst the lower branch is, generally speaking, less rich than the other two. This lode, although partially explored over a length of more than three leagues, produced the chief portion of its silver within a space of about 1,000 fathoms, and particularly from that part of the vein comprehended within the concessions of Valenciana, La Cata, Mellado, and Rayas. The Veta Madre is not, however, the only silver vein which has been successfully worked in the neighbourhood of Guanaxuato, as there are others situated a few leagues to the north, which have been opened in the concession of the Pavillon and La Luz. The first of these yields ores containing a large proportion of ruby silver, whilst the veinstone of the latter is much stained by blue carbonate of copper. The vein worked in the mine of the Asuncion, which is about a league to the north of the Veta Madre, and runs parallel with it, is, like the principal vein of the district, divided into three bands, has the Pate SILVER. same inclination, and affords ores of a very similar character. The eangue of the Veta Madre is composed of a very white quartz, con- taining numerous reniform cavernous concretions. The ores consist of native silver, black antimonial sulphide of silver, and small quantities of red silver ore, rarely associated with iron pyrites or galena, but occa- sionally with very small quantities of blende and mispickel. Gold also occurs in avery finely-divided state, and is consequently seldom visible, although grains of considerable size are sometimes met with, dissemi- nated in the quartz. The ores of Guanaxuato generally contain less than three per cent. of metallic ingredients intermixed with the quartzose gangue. According to Duport the average assay nein for silver, is from 0:0015 = 49 oz. to 0:0020 = 65 oz. per ton, and when the assay was below 0:0009, or 29 oz. per ton, the ores could, in 1843, be no longer extracted with advantage.* Ores containing more than 0-003 = 98 oz. per ton, are rarely met with, in any considerable quantities. The proportion of gold by weight is generally about 0-005 of that of silver, but this is subject to slight variations in different parts of the vein. Little is known with respect to the produce of Guanaxuato previous to 1760, when the mine of Valenciana was first opened ; but even at that time some of the other workings had attained considerable importance, since Gamboa speaks of the large gallery at Rayas as being a remarkable undertaking, and states that it was of such dimensions as to allow of mules entering the interior of the mine for the purpose of receiving their burdens.t In 1803, the workings in the Valenciana had already exceeded 200 fathoms in depth, which, as Duport remarks, is below the point at which the mines of Mexico usually begin to become impoverished. This gradual diminution in the average produce of a vein is called by the Mexican miners the enborrascado, and begins to take place in many instances even at less considerable depths. At the Valenciana, however, the ereat width of the lode, and the expectation of fresh discoveries, encouraged the proprietors to continue their operation to a depth of 350 fathoms, and efforts were made to compensate for the falling off in the produce of the ores, by the increase of the quantities treated. In this way the enterprise struggled forward until 1810, when the breaking * “De la Production des Métaux Précieux au Mexique,” par St. Clair Duport. P. 212. Paris, 1843. + Gamboa, ‘ Comentarios a las Ordenanzas,” cap. 19-20. SILVER MINES OF NORTH AMERICA. 273 ad out of the War of Independence caused the suspension of all operations at the Valenciana and many other Mexican mines. In 1822 the re-opening of the Valenciana mine was undertaken by the Anglo-Mexican Company, who agreed with the proprietors to furnish the necessary working capital on condition of receiving one- half the net profits accruing from the operations. This Company erected at a great expense powerful steam-engines for the drainage of the mines, but, on getting out the water, it was found that the ores at the lower levels were not sufficiently rich to repay the expenses of extraction and reduction, and the deeper portions of the vein were con- sequently abandoned, and operations entirely confined to the extraction of ores which remained standing nearer the surface. The working of the property was for some time continued in this way, but the results obtained were so far from satisfactory that the English proprietary finally resolved to sacrifice their expenditure and abandon the enter- prise to the original proprietors. The eperations which have been carried on since that period have afforded but very moderate returns for the capital employed, having been sometimes barely sufficient to eover the current expenses of the undertaking. The Valenciana is the deepest mine in Mexico, and the non-success of the Anglo- ~ Mexican Company has consequently tended somewhat to discourage further attempts at deep mining in the country. The extraction of the water and ore from the Mexican mines is usually effected by means of ma/acates, or horse whims, around which a rope is so wound that whilst one sack of raw hide is descending the shaft another is being raised to the surface. The Valenciana mine has several shafts, but» the principal one, or two. general, which is 734 varas,” or 343 fathoms in depth, has a diameter of nearly thirty feet, and is one of the most remarkable engineering works in Mexico. Next to the Valenciana, the mine of Rayas is the most important. The main shaft is the largest in the country, and was made to rival that of Valenciana. It is in the form of an octagon thirty-one feet in diameter, and secured by masonry for a depth of about thirty varas from the surface. Its total depth is 465 varas, or 215 fathoms; but its diameter is smaller downward than towards the surface. Some of the best constructed malacates in Mexico have been erected at the mine of Rayas, and at the time this neighbourhood was visited by Mr. J. Phillips (1840), each of them was worked by twelve horses driven round at a fast trot, and drew the dota, which when full of water * The Vara equals 33:°384 inches. As QA 7 SILVER. weighed 1,500 lbs., from a depth of 465 varas to the surface, in eight minutes. — In the district of Zacatecas and Real del Monte the veins are very numerous and cross each other in various places, although generally at the same angle, whilst at Guanaxuato the riches are to a greater extent concentrated in one enormous lode. The large size of this vein, and the impossibility of thoroughly trying the ground without having recourse to numerous cross-cuts, gave rise at Guanaxuato to a method of working very much resembling the tribute system of Cornwall. The miners who work on this system, which has been attended with the best results, and has led to the discovery of some of the richest deposits of ore, are called buscones. In this way the men, to a great extent, work the mines at their ownrisk, and by following up such indications as may appear to them favourable, they often meet with valuable courses of ore; whilst, on the other hand, they sometimes work for many months without gaining more than sufficient to provide them- selves with the means of bare subsistence. The buscan receives a certain proportion, sometimes one-half the produce of the ore which he breaks, and should he fall in with a rich deposit his gains will necessarily be very large, instances not being wanting of a man making in this way from a thousand to fifteen hundred dollars per month. In cases of this kind, however, it is optional with the owners of the mine to take the discovery out of the hands of the miners after giving them a certain notice; when this is done, each man is paid a dollar per diem without allowing him any portion of the ore. A very large proportion of the ores at Guanaxuato are, however, raised by buscones, who divide the produce of their labour with the proprietors of the concessions. ‘The ore, after being broken and separated as much as possible from sterile matter, by hand picking, underground, is usually put into botas of bullocks’ hide, and drawn to the surface by malacates. In some of the mines, however, the ore is taken to the surface on the backs of labourers, who, with a load of from two to three hundred pounds, make several journeys daily from the bottom of the mine, often a depth of from four to five hundred varas, to the surface. At the mine of Mellado an inclined railway is em- ployed for this purpose. When brought to the surface, the ore is | conveyed to the mine yard, where it 1s placed in separate heaps under the care of the buscon, who picks out a further amount of sterile matter, and prepares the ore for sale. One day in each week is gene- rally fixed for the sale of the ores, and the miners may then be seen SILVER MINES OF NORTH AMERICA. 275 laying out their several parcels, so as to make them appear to the best advantage, by turning each stone in such a way as to expose the best side of it, and keeping his lot constantly sprinkled with water, which has the effect of making the mineral look darker and richer. The various purchasers, or rescatadores as they are called, take, as nearly as possible, an average sample from each lot, which is ground into a fine powder, and subjected to a sort of assay on the spot. This is effected by washing a handful of the pulverised ore in a jrcara or small bowl, formed of half a gourd; and after washing away the lighter earthy particles, the richness of the parcel is estimated in accordance with the amount and appearance of the mineral deposit remaining in the bowl. Long practice enables those who constantly employ this process to arrive at results very closely approximating to the true yield of the ores, but many of the purchasers now prefer to regulate their bids by the result of fire assays, and in this case the samples are taken on the day previous to that on which the sale is to take place. When the hour of sale arrives, a bell strikes as a signal that it is about to commence, and the person entrusted with its management takes his place successively at the foot of every parcel. ach pur- chaser, in turn, now approaches, and whispers in the ear of the sales- man his bid for the parcel at the foot of which he stands; and when all have given in their prices, the lot is adjudged to be the property of the highest bidder. When two persons offer the same price, the first bidder obtains the parcel. The salesman and purchasers thus move from lot to lot, until the whole of the ore in the yard has been disposed of, after which it is removed by the various buyers at their own expense. The quantity of ore contained in each parcel is not ascertained by weighing, but, like the assay by washing, is determined with great accuracy, by the eye, by those who have had long practice in the business. | Zacatecas.—Lhe district of Zacatecas is situated about fifteen leagues east of the elevated mountains which join the principal chain of the cordillera extending from Durango to Guanaxuato. Burkart, who lived many years in this vicinity, and who had consequently ample opportunities of becoming acquainted with the geology of the country, considers that the greenstone which encloses the greater number of the veins in that locality can only be regarded as a diorite. Busta- mante, on the contrary, calls it syenite. This rock, which at some ive 276 | 3 SILVER, points presents many of the characteristics of chloritic slate, overlies a blue argillaceous slate which occasionally comes to the surface, and closely resembles that forming the enclosing rock in the deepest por- tions of many of the Mexican mines. Quartz veins are exceedingly numerous in the neighbourhood of Zacatecas, and have generally a direction approaching north-west and south-east. The Cantera vein 1s remarkable, not only on account of its variation in direction at different points in its course, but also for its prominent outcrop, which may be traced on the surface over a length of more than three leagues. This outcrop, which sometimes stands at a height of a hundred feet, and is from forty-five to sixty feet in width, throws off a branch towards the north, which is known as the San Martin vein; whilst the principal lode, turning towards the south, takes the name of the Del Muerto, and finally makes an intersection with the Quebradillas. This vein, which has a dip of 35° towards the south, is for a long distance enclosed between a greenish slate on its foot wall, and sandstone on the hanging wall, but finally enters the green slate, which thus con- stitutes the enclosing rock on either side. The principal workings on this vein, which is at this point about 36 feet in width, produced large quantities of ore, yielding by amalgamation from 0:0010 to 00012, or from 33 to 39 oz. of silver per ton; but the workings having been badly secured, fell in some years since, and caused the abandonment of the mine. | The San Bernabé vein was first opened by the conquerors of Mexico in 1548, and is said, in common with the San Alvado, to have been worked by Cortez. The eastern extension of this vein, which dips to the south, and of which the direction is nearly east and west, has produced large quantities of ore in the concessions of Malanoche, Rondanera, Loreto, and Peregrina; but the most productive mines of Zacatecas, in 1843, were those of San Clemente and San Nicolas, of which the workings were commenced in 1836, to the east of the mines above mentioned. In the various workings of the old mines, the width of this vein was from twelve to thirty feet, but in the San Cleménte and San Nicolas it rarely exceeds six feet, although the selvages of clay on the walls, which frequently have a considerable thickness, are so impregnated with argentiferous matter as often to admit of being worked with as much advantage as the lode itself. The most important vein of Zacatecas is the Veta Grande, which | has been worked over an extent of nearly 2,500 fathoms. The first extensive operations on this lode were undertaken in 1765, by a SILVER MINES OF NORTH AMERICA. 277 M. Laborde, a Frenchman. The general direction of the vein is north 60° west, with an inclination of about 35° towards the south, and like the Veta Madre of Guanaxuato, it is divided into bands, which some- times have an united thickness of seventy-five feet, but of which the average width may be taken at about forty feet. Of this width about twelve feet are occupied by country rock, dividing the lode into three bands. The gossans, or colorados, usually extend to a depth of forty fathoms, and contain native silver and chloride of silver; the ores below the water level consist of various sulphides of silver, asso- ciated with a little blende, galena, and iron pyrites. A bonanza, or bunch of ore, discovered in this vein, and worked from 1828 to 1838, yielded a net profit of above $9,000,000 to the proprietors of the mines. According to Bustamante and Burkart, the Veta Madre produced from 1790 to 1833, 3,902,252 marks, or about 2,500, 000 Ibs. of silver.* Where first worked by the Bolahos Company, the vein-stuff, as extracted from the mine, was so generally productive, that only one- sixth had to be rejected as not paying the expense of reduction. Gradually, however, the vein became so much impoverished, that not quite two-thirds could be treated with advantage. During the former period the proportion of silver extracted by fusion was one-fifth of the whole production, whilst, during the latter, ores sufficiently rich for this method of reduction were very rarely met with. The average produce obtained from the ores of the Veta Grande at the Hacienda de la Sauceda from 1804 to 1839, was as follows :— 1804 t0 1808 . . . 0°0025 = 81 oz. per ton of 2,240 lbs. 1820,, 1824 . « . 0°0021 = 68 “4 ” ” 9 1825 ,, 1882 . . . 0°0019 = 62 + - 99 ” 1839 ».« « O0017 = 55 ” ” ” ” It must, however, be remarked that the produce obtained by no means represents the actual richness of the ores treated, since from the large quantities of antimonial silver present, the patio process failed to extract nearly the whole of that metal, and this loss is estimated by Duport at nearly two-fifths of the total contents of the argentife- rous matter subjected to amalgamation. The Veta Grande, however, like all the principal veins of Mexico, begins to diminish in rich- ness at depths, from the surface, varying between 75 and 150 fathoms. Another important vein in the district is that of the Tajos de Panuco, * The Spanish mark equals 3,550°5 grains, 278 SILVER. on which open workings were commenced in 1548, and extended over a length of above three hundred and filty fathoms. The silver from the Veta Grande contains but a very small proportion of gold ; that from the San Bernabé often affords from 0°001 to 0:003 of this metal. The following table, from Duport, will afford an idea of the produce of the mines of Zacatecas— Marks. Tbs. troy. From Ist June, 1548, to 16th September, 1810 . 67,317,937=42,161,224 . », 16thSeptember, 1810, ,, 1st-June, 1818 . 2,296,472= 1,438,484 on dab Onno. isis; ., r 1825 . 2,107,350= 1,319,833 no - 1825, ,, 3lst December, 1832 . 3,532,769= 2,212,573 The operations of the English Company were suspended in 1838, after which time the produce of the mines continued gradually to diminish, and in 1842 some of them were let out to buscones at a partido, or share of one-fourth, which in 1846 had been increased to one-third. Fresnrito.—The Cerro de Proaia is situated fourteen leagues north- west from Zacatecas, and consists of an elevation of about six hundred yards in length, which does not exceed three hundred feet in height above the level of the surrounding plains. This hill is composed of a compact argillaceous rock overlying, at a certain depth, a blue slate containing bands of white quartz. In these rocks there exists a considerable number of veins running nearly north and south, and generally dipping towards the west, but at such variable angles that the different veins often intersect each other in depth, thereby forming a species of network. The whole surface of the mountain is here covered by the débris of former workings, and large open cuttings are seen, forming more or less continuous trenches on the course of the different veins. | These mines are known to have been worked by open cuttings and otherwise, as far back as 1755, but about the year 1760 operations were commenced on a more extensive scale, and abundant returns obtained over a considerable extent of ground. Mining was subse- quently carried on by some merchants of the city of Mexico, after- wards by the State of Zacatecas, and later under the auspices of the Central Government. Raat vet Monrz.—The mines of Real del Monte are situated about sixty miles due north from the city of Mexico, in a district containing SILVER MINES OF NORTH AMERICA. 279 mumerous bands of porphyry of evidently different ages. To the north-east of Real del Monte the porphyries are covered by columnar basalt, and at a still greater distance, in the same direction, by meta- morphic slate. The rock enclosing the various argentiferous veins of this locality is a decomposed porphyry, in which the presence of horn- blende is announced by numerous greenish stains. The principal veins of Real del Monte run nearly east and west, whilst the cross- veins course almost north and south, the inclination of the former being to the south, and of the latter towards the west. The principal east and west vein of the Real del Monte is the Biscaina, usually about fifteen feet in width, but there are numerous others, particularly near the town of Pachuca, which have nearly the same direction, whilst these are crossed by the Santa Brigida, and others. The partido system has prevailed among the mines of Real del Monte from a very early period, but differs somewhat in its arrangement from that of the other mining districts. Here the working miner or barre- tero receives a certain portion, frequently an eighth, of all the ore he raises, and in addition is paid a daily sum equal to about two shillings. From the Real del Monte Company having been the first of the large associations organised in this country for working mines in Mexico by the aid of British capital, some notice of its history and progress may not be uninteresting. Real del Monte Company.—But little is known of the mines of Real del Monte, prior to the year 1749, except that they had yielded considerable quantities of silver from irregular and detached surface workings, and had at last become almost entirely abandoned from the influx of water, as the excavations increased in depth. At the above period, Don Pedro Terreros, a merchant of Queretaro, joined a practical miner named Bustamante, in a general denuncio of the district, by which they obtained possession of its two principal veins, La Biscaina and La Santa Brigida, on the condition of effecting their drainage by means of a horizontal gallery. For this important work, a point was chosen sufficiently down the slope of the northern descent of the valley to ensure its entering the principal mines of the Biscaina vein at the depth of one hundred fathoms from the surface ; but as the dis- tance necessary to obtain this difference of level was nearly 1,500 fathoms, the work, although commenced in 1749, was not completed until 1759. Bustamante did not live to see the result of his great work, but Terreros persevered to reap the reward ; for, having by this adit freed the mine from water, he extracted at comparatively small cost, up to his death in 1781, the large amount of fifteen millions of dollars, having been previously ennobled by the King of Spain, under the title of Conde de Regla. His successor, the second Conde, continued the working of the mines, but not to equal profit with his father, who, having exhausted the upper portions of the veins, 280 SILVER. rendered dry by the adit, left his son the more difficult task of contending with the water under that level. This drainage was effected by malacates, which, raising the water in skin bags to the level of the adit, were for some time sufficiently effective, but gradually, as the mine became deeper, the difficulty and cost of drainage with such imperfect machinery also augmented. In the year 1801, the twenty-eight malacates then at work, occupying twelve hundred horses, with four hundred men, and costing $250,000 per annum, were not found sufficient to keep down the water to fifty-four fathoms below the adit, to which depth the workings on the Biscaina vein had attained in the mines of Santa Teresa and Guadalupe ; and consequently, although these mines were then producing at the rate of $400,000 annually, the drainage was suspended, and their deeper workings abandoned. After this the workings were limited to a higher level ; and on the hitherto unexplored extensions of the vein, and up to 1809, when the second Conde died, the mines of San Ramon with some others continued to yield about $300,000 per annum. From this period the produce of the mines gradually decreased, and the War of Independence having commenced, their working was entirely suspended in 1819; the total produce since the death of the first Conde having been $10,000,000. After the recognition of the independence of Mexico by Great Britain, the attention of English capitalists became directed to the mines of that country, and, at the suggestion of the late Mr. John Taylor, an association known as the Real del Monte Company was formed for restoring and draining the mines belonging to the Regla family. In July 1824, Captain Vetch of the Royal Engineers, the first commissioner of the Real del Monte Company, arrived at the Mines, which he found in a state of utter ruin; most of the shafts had fallen in, leaving their former sites only to be detected by immense hollows overgrown with brashwood. A still more serious evil was the destruction of the great adit, which having in many parts so gone to ruin that it no longer carried off the water, it consequently rose to a great height in the mines. All the machinery in the large reduction works was gone, the population had become very scarce, and the town a collection of ruins. The chief inducement of the new Company to resume the drainage of these deep mines, being the advantages they expected to derive by the substitution of steam-power for the imperfect and costly one of horse machines raising water and ores in skin bags, a body of miners and mechanics, with steam-engines, pumps, and other machinery, arrived at Vera Cruz in May 1825, under the charge of the late Colonel Colquhoun of the Royal Artillery. The rainy season commenced shortly after, attended by its usual scourge, the yellow fever, and soon made sad havoc among both English and Mexicans, Colquhoun, however, persevered through all difficulties, and by May 1826 the engines had arrived at the mines. In the meantime the district of Real del Monte had been carefully surveyed, the great adit cleared and restored, many of the shafts had been repaired down to adit, and buildings, workshops, and stores were rapidly rising around the mines. From this period the work of clearing and restoration pro- gressed steadily, until by the end of 1829 the drainage had been effected to the depth of fifty-four fathoms under adit. The annual cost of pumping did not exceed 830,000, being an immense saving as compared with the large sum of $250,000 which the twenty-eight malacates formerly employed for this purpose had cost the second Conde when at the same depth be abandoned the lower workings. It, however, soon became evident that the drainage at the distant points of San Cayetano and Dolores was not sufficiently effective for working the richest portions SILVER MINES OF NORTH AMERICA. 281 of the vein in the mine of Santa Teresa: a new vertical shaft was consequently sunk, and a more powerful engine erected. An engine of fifty-four inch cylinder having been erected, and assisted by the smaller ones at Dolores and San Caye- tano, this portion of the Biscaina vein was worked for some time with considerable profit, and to the depth of 235 fathoms from the surface, or 120 fathoms under adit. At this point the water having so increased as again to overpower the engine, a still larger one of seventy-five inches was erected at Dolores. The reward of this expenditure was two bunches of rich ore, the one discovered on the Santa Brigida vein near Acosta, and called La Luz; the other at San Enrique, on the Biscaina vein near Dolores. Up to the end of 1847, however, the general result of working the mines had been decidedly unfortunate to the English adventurers; for although they had profited by three rich bunches of ore at Terreros, Acosta, and Dolores, and had produced $10,481,475 worth of silver, the outlay on all the undertakings of the Company had also reached the amount of $15,381,633, leaving a loss of nearly five millions of dollars as the result of the twenty-three years they had held the mines. The deep workings were now 120 fathoms under the great adit, or sixty-one ‘fathoms below the point at which they had been abandoned by the second Conde, and the difficulty of drainage had so increased, both from the augmented quantity of water, and the greater height to which it was necessary to raise it, that three powerful steam-engines, which were discharging two thousand seven hundred gallons per minute, at a cost of $90,000 per annum, could barely stem the coming water of the mine. To show the difference of the cost of steam drainage as com- pared with the plan of the country, becomes at this point interesting. The English Company, at the commencement, had easily effected with two small engines, and at a cost of $30,000, what the Conde de Regla had been obliged to relinquish in 1801 with twenty-eight malacates, and at an annual cost of $250,000; but with the increased depth, and greater volume of water, three pumping engines expending $90,000 were barely able to maintain the drainage, while to replace them would have required at least one hundred and eighty malacates, employing seven thousand horses, with upwards of two thousand men, and an expenditure of not less than two millions of dollars per annum. With this increased difficulty of drainage, seeing their rich bunches of ore all worked out, and a debt of five millions of dollars still outstanding, it is not surprising that the energy and perseverance of the English adventurers were at last exhausted. Towards the middle of 1848, Don Manuel Escandon and Don Nicanor Beistegui were induced by Mr. Buchan, the manager of the mines under the original Real del Monte Company, to take up the enterprise on terms which, although not returning to the English adventurers much of their lost capital, at least relieved them from all further responsibility. After having carefully examined the position of the enterprise, this gentleman came to the conclusion that the concern had hitherto been worked, as well on too limited a scale as with too expensive an establishment ; but particularly that without any effec- tive attempt to render the poorer and more abundant ores available, or to make new discoveries on the higher and still virgin portions of the veins, every effort had been directed to the search after rich ores in depth, which, when at last discovered, did not repay the large amounts expended to find them. With reference to this subject Mr. Buchan remarks :—“ Experience had convinced me that to render an extensive mining enterprise secure, it should mainly depend on the poor and abundant ore of its veins for the current cost of exploring them, so that the richer bunches, which would 282 SILVER. occur in a regular and systematic process of working, might be found without any forced effort or outlay, and thus become more profitable. It was further clear that as certain costs, such as general management, drainage, rents to owners, &c., were unavoidable and nearly the same under any scale of operations, that a larger return of the poorer ores must be obtained, in order to support them, and lastly that a perfect system of economy in every branch of so large an establishment, was most essential to its success.” * To carry out these views, he commenced by arranging the entire system of accounts on such a plan that every week’s result, in each mine and reduction work, might be clearly shown, and the economy of the different departments thus fairly compared with each other. To reduce the excessive cost of drainage, he abandoned the very deep workings on the Biscaina vein, and only maintained the water to sixty-five fathoms under adit by one large steam-engine, while at the same time the extraction of poor ores was facilitated, and increased by additional shafts, winding machines, and internal rail-roads. Conjointly with these operations the eastern and yet virgin portions of the Biscaina vein were selected for the site of new trials, in high ground above water level, and another trial was commenced at Pachuca in the Rosario mine. Here the Company had already worked and incurred a considerable loss by extract- ing ores from the old mine, but finding that the famous vein of Xacal would intersect that of Rosario, to the eastward of all former trials, it was determined to take advantage of an adit, already considerably advanced, to examine so promising a point. After driving this adit some sixty fathoms, they had the good fortune to meet with the expected intersection of the veins, from which a considerable extraction of ore was at once commenced. It is a peculiarity of the mineral veins of this district, that while those which run in an easterly and westerly direction produce ores readily reduced by the usual amalgamation process, practised to so great an extent in Mexico, the ores from the north and south veins have a different mineral character, and in many cases will not yield their silver by this process. Trials having, however, proved that they could be advantageously reduced by a modification of the well-known barrel system of Freiberg, and the great mass of the poor ores being of this character, it was determined to adopt barrel amalgamation on a very large scale. For this purpose, two new works were erected at San Miguel and Velasco, whilst those of Regla and Sanchez were enlarged and modified. In the haciendas of San Miguel and Regla, which are at a distance of twelve miles from the mines, water-power is alone used to: drive the machinery, blow the furnaces, grind the ores, and revolve the barrels ; but at those of Sanchez and Velasco, built at the mouth of the valley descending from the mines, steam is employed as an auxiliary power ; so that in 1855, besides the powerful pumping engine of seventy- five inch cylinder, which drained the mines, there were, at the reduction works, two smaller rotatory engines and eighteen water-wheels of different sizes, which drove 110 wet stampers, sixteen large arrastres, and three edge mills, all employed in grinding ores ; besides revolving sixty-four large barrels in which the prepared ores were amaloamated. In the hacienda of Regla were eight blast furnaces for smelting rich ores ; and in San Miguel, Velasco, and Sanchez, thirty-six reverberatory furnaces for drying and roasting the ores preparatory to amalgamation in barrels. We are informed by Mr. Buchan that a great increase in the reduction works has * Report of the Real del Monte Company, 1855. SILVER MINES OF NORTH AMERICA. 283 been made since 1855, by the erection of the hacienda of Loreto, which, situated in the midst of the Pachuca mines, has already the power of reducing yearly 55,000 cargas of ore by the patio process, and is being otadually increased, so as to be enabled to treat 100,000 cargas annually.” The machinery employed by the Real del Monte Company having been much increased since 1855, the following are now in operation :— Steam Engines for Drainage. 1 of 75 in. cylinder on the Dolores Shaft. 1 of 54',, :, . Acosta », Real del Monte. Ha OL 305 mr r San Patricio ,, Ae i eat, Bhs, if - San Juan ,,_ Pachuca. Leer er Sh; " 4 San Nicolas ,, 4. by, or 2075, a i Corteza a . i ofik 5; Pr 3 Rosario Ss se Total drainage — 7 steam-engines. Rotary Engines. 1 San Juan Shaft, Pachuca ; winding, 1 Rosario ~ - ‘4 1 San Pedro ss . ¥ 1 Velasco hacienda ; driving barrels. 1 = Sanchez 7 , ? 3. In workshops, turning lathes, blowing, &c. Total rotary — 8 Grand Total —15 steam-engines. Water-wheels. 3 Loreto reduction works ; one pumping and two working stamps. 1 Guerrero Fr Ss wet stamps. 2 Aviadero = re ss 1 Sanchez “ driving barrels. 1 Velasco he ms FA 2 Penafie i a driving wet stamps. 6 San Miguel _,, 2 two wet stamping, four driving barrels. 11 Regla e 4 one 7 ten working arras- tres, &e. 2 Regla smelting works ; blowing and stamping. Total 29 water-wheels. The present grinding machinery amounts to 350 stamp heads, 24 water-power, and 50 mule-power arrastres, and 80 amalgamating barrels ; which reduce yearly— Cargas, By the barrel process . . . « « « 206,000 tinge th ore ae ne eee Se TUG. 000 Total 312,000 * The carga weighs 300 lbs. 284 . SILVER. The following summary of the operations of this Company for 1860, which was one of the most favourable years, the produce being good, and the amount of dead- work small, is of great practical interest :— General Results of Mining Operations by the Rea! del Monte Company, im the districts of Real del Monte and Pachuca, in the year 1860. General expenses of management . . . . . . « $50,170 Cost of draining the two districts . 2°. ..+. . 167,934 Cost of extracting ores from various mines . . . . 647,338 Cost of reducing ores in different haciendas . . . . 841,606 Duties on silver, paid to the Mexican Government . 173,587 Freight of ores from mines to reduction works, inclu- ding cost of repairing roads . . . . + ve 186,503 Convoys of silver to the coast, or mint of Mewes sta 14,877 Agencies, Commissions, &¢ 4 #4» a ties be 7,109 Total cost on current working of the mines . . . . 2,089,124 Total produce, 277,396 cargas of ore, from which were extracted 423,394 marks of silver, value. . . . 3,710,891 Profit on current working. . . . $1, 621 767 The above profit was applied as follows :— Re-invested in discovery works in different mines . . $181,052 Re-invested in enlarging and improving works for the TOdUCHION: Of (GES jzy Sin? Se rele ete Reta eae 73,120 Purchase of forests for fuel . . . . richie 31,000 Cost of maintaining a force of 150 ee and 50 infantry, necessary for the security of the districts dure the ciyal war #2 ies ee BP ae eee 60,000 Paid as dues to part owners of mines . . ae eo 353,070 Paid as dividends to the Shareholders of the Coneus 923,525 Total, . $1,621,767 Table of stores consumed during the year 1860 :— From forests belonging to the Company— Tin bertc. ck oom ee Sy eee Se he ee OD, Weood-fael 2 50) ar, ay ew taenay ene, OD OHarcodls =e ee ee nen ee Oe) —_—_—— $290,000 aU piee ec oye re VE ae ee ere ere) Cie ost Ver ol veal Tra gs ee ee) COO) Pron wana Steel < 42a eo cca oo ae ee —_——- 300,000 Carried forward . . . . $590,000 SILVER MINES OF NORTH AMERICA. Barley and Straw Tallow and Oil Gunpowder. . . Sulphate of Copper Sacks and Cordage Lime and Bricks . Litharge Leather and Hides Sundry stores . Brought forward . . ° Total ie t- . $500,000 $ 100,000 40,000 15,000 14,000 18,000 10,000 13,000 15,000 45,000 270,000 <1 ae, £8 A SB BGL000 TABLE showing the details of Silver Ores reduced by the Real del Monte Company, in the districts of Real del Monte and Pachuca, from May 1849, when the present Company was first formed, to the end of the year 1865. Ores reduced by smelting. Hee, Ores. | Silver. |cargas | inarks. 1852 | 7,108) 45,671 1853 | 2,903] 15,358 1854 | 2,386] 14,913 1855 | 2,690} 23,612 1856 | 6,011} 48,666 1857 | 4,926] 44,942 1858 | 5,056| 49,582 1859 | 4,813] 52,057 1860 | 4,698| 47,442 1861 | 4,162] 42,397 1862 | 4,203] 47,518 1863 | 3,543] 32,983 1864 | 3,500| 29,067 1865 | 1,921| 19,273 57,920 | 513,481 Ores reduced by Ores reduced by Barrel Patio Total each Year. amalgamation. amalgamation. Es ra Se ee eo) - | mS ahe |e On & wee ores. | Silver. | Ores. | silver.| 22 | 328 |Be88| S226 £3 HHS |Rans|asnk BF 2 de wed Va a s ay cargas. marks. | cargas.| marks. | cargas. | marks. | dollars. | marks. 281,629] 221,827} 21,975) 19,412; 310,712} 286,910] 2,508,655 9°00 141,208] . 131,518| 37,040] 29,063} 181,151] 175,939] 1,537,796 9°71 152,614| 160,900) 37,982| 31,313} 192,982] 207,126| 1,811,822) 10°73 181,353| 217.193] 38,010| 46,868) 222,053] 287,673| 2,375,503) 12°90 209,053| 248,041) 46,490} 58,843) 261,554) 350,550) 3,081,663) 13°40 219,326| 238,041} 50,400!) 63,183) 274,652) 346,166] 3,039,019) 12°50 217,461| 218,291} 48,355| 53,638) 270,872] 321,511] 2,824,831) 11°80 226,775} 283,112| 44,013} 51,434] 275,601| 386,603/ 3,404,459) 14°00 222,498] 314,745] 50,200] 61,207| 277,396] 428,394) 3,710,891) 15°20 212,480| 263,990| 63,947| 87,545} 280,589| 393,932) 3,782,399) 15°70 209,861} 310,906] 60,412] 73,968| 274,476} 482,392) 3,445,222) 14-00 194,097] 217,204| 76,920| 88,370) 274,560) 308,557] 2,984,351} 12°30 205,850}. 229,946 | 105,740 | 142,697) 315,090| 401,710) 3,432,107; 12°40 170,600| 186,535| 97,642 144,055 | 270,163) 349,863) 3,044,572) 13°00 2,844,805] 3,237,249 | 779,126 951,596 | 3,681,851 | 4,702,326 40,983,290} 12°77 * The monton varies in the different mining districts, but, in Real del Monte and Pachuca, is 10 cargas, or 3,000 lbs. 443°8 gr. each. The mark of silver is 8 Spanish oz. of 286 SILVER. Propucs and Prorit of the Silver Mines worked by the Real del Monte Company, in the districts of Real del Monte and Pachuca, Mearco. Profits paid. ‘ Value Duties on Silver Cost of Onn: As Dues to In eons Governen Sone Part Owners. Shareholders. Four Years, to dollars. dollars. dollars. dollars. dollars. Dec. 1852 | 2,508,655 selec eel ae Fee 101,109 | 215,541 1853 1,537,796 152,681 256,250 66,015 69,344 1854 1,811,822 199,371 307,500 82,566 83,707 1856 | 2,375,503 194,511 461,250 108,604 86,815 1856 3,081,663 276,652 820,000 140,441 115,886 1857 3,039,019 241,553 461,250 138,375 107,286 © 1858 2,824,831 233,294 410,000 130,860 128,377 1859 3,404,459 364,858 666,250 158,939 120,777 1860 | 3,710,891 448,905 871,250 173,587 | 167,934 1861 3,782,399 433,963 820,000 175,359 156,627 1862 3,445,222 341,018 334,500 159,620 143,075 1863 2,984,351 178,936 557,500 138,466 174,135 1864 3,432,107 279,377 580,000 159,437 178,856 1865 3,044,572 POG, OL. ollie cs akint 141,064 212,713 $40,983,290 |$3,637,307 ($6,545,750 ($1,874,442 |$1,960,873 Total dividends to Shareholders of Real del Monte Company 6,545,750 Paid as dues to part owners of Mines Spee 3,637,307 Duties to Mexican Government . . . . . 1,874,442* Total profit of the Real del Monte and Pachuca mines, 17 years $12,057,499 Mr. Buchan, to whom we are indebted for the foregoing statistical information, remarks :— “That no dividends were paid to shareholders of the Company in 1865, must not be attributed to any failure of the mines themselves ; but that during the very unsettled state of Mexico, our expenses were greatly augmented by the increased price of materials, and the loss incurred in keeping up a considerable military force for the security of the district. Contributions and forced loans to different govern- ments have for several years past been exceedingly heavy ; but with the hope of their speedy repayment, these sums have been carried to a ‘Suspense Account,’ until the amount became so large as to determine the Company to suspend divi- dends, and dedicate all their share of profits to the liquidation of this debt. “ All the accounts I receive from Mexico assure me that the state of the mining negotiation is as promising now, as at any former period. — * Legal dues, not including forced loans. SILVER MINES OF NORTH AMERICA. 287 a “The great formation of ore in the Rosario vein of Pachuca, which, since its discovery in 1850, has yielded 25 millions of dollars, still promises a steady con- tinuance of its produce ; and although by underlie south, and extension south- ~ eastward, this orey ground is now passing gradually out of the old mine of Rosario into the neighbouring setts of San Pedro and Guatimotzin, to the benefit of the owners of these latter mines, yet this will in no way affect the Company, whose interest is equal in all. “The mine of Xacal, on the same vein, and adjoining Rosario to the west, which in former times was so famous for its richness, and the chief inducement for the drainage of the Pachuca district, has hitherto proved a great disappointment, by being found poor in its lower workings. But the works of discovery which have been steadily prosecuted into new ground, are now opening out what appears so rich and extensive a body of ore, as promises to entirely change the character of this mine. Many of our other mines are also in good produce ; and if the unsettled state of Mexico does not interfere with our mining operations more than it has hitherto done, the coming year promises to be a very profitable one in Real del Monte, but more particularly so in the Pachuca district.” NevapA.—Althouch the discovery of silver in this region can only be said to date from 1859, its extraordinary production has already rendered it more famous for its mineral wealth than localities in which this metal has been for centuries continuously mined in large quantities. This abundance of mineral wealth has attracted a numerous and industrious population to a cotintry before but thinly inhabited by tribes of wandering savages ; and flourishing towns have already sprung up in a desert which, from its situation and inhospitable character, seemed for ever to defy the progress of civilization and the arts. The two principal mining centres of Nevada are Virginia city in Storey County, and Austin in Lander County; and, although numerous veins are being more or less extensively worked in other portions of the State, the mines in the vicinity of these towns have hitherto been more productive than those of any other mineral region. Great Comstock Vutv.—The range of the Washoe mountains, in which the Great Comstock Vein is situated, is separated from the eastern slope of the Sierra Nevada by a continuous meridional depression, in which are the deep-basins of the Truckee, Washoe, and Carson valleys. Its shape is irregular, but its general direction is from north to south. In a southerly direction, it gradually slopes down to a smooth table- land, traversed by the Carson river, beyond which the Washoe moun- tains become merged into the more elevated Pine-nut range. Towards 288 SILVER. _ the west, the Washoe hills descend rapidly, and finally sink beneath the detrital beds of the Washoe and Truckee valleys, but are con- nected with the Sierra Nevada by two low granitic ridges, stretching across the northern and southern extremities of Washoe valley. To the north-east, this range passes into a very extensive, and but little explored, mountain region; whilst to the south-east it abruptly dis- appears below one of the basins of the Carson river. The entire width of this range is not above fourteen miles, whilst its length is not yet determinable, on account of the scanty knowledge possessed of the northern portions of the State. The culminating point of the Washoe range is Mount Davidson, the elevation of which, as deter- mined by Whitney, is 7,827 feet ; and at its foot are situated Virginia city, and the principal mines on the Comstock lode. The aspect of the Washoe mountains is exceedingly barren, as is also the view from Virginia, over the hilly country to the east. The air 1s, however, extraordinarily pure and transparent, so that every ravine and declivity on the sides of mountains a hundred miles dis- tant is readily distinguished. At the time of the discovery of the Comstock vein, the Washoe mountains were covered by scattered and stunted trees, of nut-pine and cedar; but these have long since dis- appeared, and Virginia now depends for her supply of. wood on the slopes of the Sierra Nevada. The enormous consumption of wood for fuel, and of square timber in the mines, is, however, rapidly causing the destruction of these forests ; and the time is, consequently, not distant when the mines and reduction works of Virginia must derive their wood from greater distances, and chiefly from near the Truckee River, which is about thirty miles from the mines, and to which a railway, in connexion with the Central Pacific Railroad, is projected. Mount Davidson, the prominent central point of the Washoe range, consists of syenite, which is here composed of two kinds of feldspar, orthoclase and oligoclase, associated with hornblende, mica, and occasionally epidote. Metamorphic rocks adjoin the syenite on the north and south, and are intersected by dykes of that rock, which of itself sufficiently proves its later origin. These metamorphic rocks differ materially in their lithological charac- teristics, but may be divided into three distinct groups, the most recent of which belongs to the triassic epoch. These are immediately preceded in age by a series of micaceous and quartzose slates, fre- quently containing bands of limestone; below which is a third series, chiefly consisting of hornblendic rock, with interstratified layers of SILVER MINES OF NORTH AMERICA. 289 quartzite, grey slate, crystalline limestone, and specular iron. These rocks form the hills which flank American Flat to the west, as well as those between Silver City and Carson, and are generally capped by an: overflow of porphyry. They constitute the ancient serves, and par- tially preceded, and were partly contemporaneous with, the gradual upheaval of the Sierra Nevada and the entire chain of the Cordilleras. The recent serves, which 1s volcanic and eruptive, belongs to the latter part of the tertiary and beginning of the post-tertiary periods. The first of these in point of age is a species of dioritic porphyry, to which Richthofen has applied the name of propylite. This rock has the peculiarity of exactly resembling many ancient rocks in appear- ance, whilst in reality it is of very recent origin. It occupies a pro- minent position among the enclosing rocks of the Comstock vein, and likewise encloses a considerable proportion of the largest and most productive silver veins in various parts of the world. Among these may be mentioned the silver veins of the Carpathian Mountains, those of Zacatecas, and other localities in Mexico, and probably, also, many of those in Bolivia. This rock is composed of a fine-grained paste, generally of a greenish, but sometimes of a red, grey, or brown colour, with embedded crystals of oligoclase, and columns of dark- green fibrous hornblende, which is also the colouring matter of the base itself. A peculiarity of this rock is its ferruginous character, when decomposed by weathering. Geologically, it is an eruptive rock, but has been accompanied by vast accumulations of brecciated matter, which are sometimes found regularly stratified. Several dif- ferent kinds of volcanic and eruptive rocks followed the outbreak of propylite; but of these, trachyte is the most important, not only as taking a prominent part in the formation of a large extent of country, but also on account of its intimate relations with the formation of the Comstock vein. Its essential characteristic is the predominance of glassy feldspar, which, along with hornblende and mica, is embedded in a paste of a peculiarly rough texture, caused by the presence of an infinity of microscopic vesicles. Eruptions of basaltic rock, of considerable magnitude, have taken place in various parts of the great basin; but in the neighbourhood of the Comstock vein they have not made their appearance to any important extent. Volcanic and eruptive agency appears to have gradually declined in the whole region, leaving the last trace of its active existence in the still boiling waters, and daily increasing silicious deposits, of Steamboat Springs. U 290 SILVER. The Comstock vein runs nearly in the direction of the magnetic meridian, alone the eastern slope of the Mount. Davidson range, a - little above the slope on which are built the towns of Virginia, Gold Hill, and American City. The outcrops extend in a broad belt along the foot of the mountain, and immediately at the back of the three towns. The course of the vein, as far as it has been hitherto explored, appears to be more or less modified by local circumstances, passing the ravines in concave bends, and enclosing the foot of the different ridges in convex sweeps. These irregularities are of considerable importance, as they would seem to influence the ore-bearing character of the lode. The length to which the Comstock vein has been traced with certainty 1s somewhat over nineteen thousand feet, while its total extent is probably at least twenty-four thousand feet. The most extensive operations have been carried on between the Ophir Mine, north, and the Overman, a distance of about eleven thousand feet ; whilst in other parts the workings have been of a very superficial character. Several of the mines are worked to a depth of six hundred feet; but the shafts of the Hale and Norcross, Chollar Potosi, and Gould and Curry, have reached a depth of above eight hundred feet. The Comstock vein, at a depth of from four to six hundred feet below its outcrop, has a width of from one to two hundred feet; but contracts in some places, so that its two walls come into close proxi- mity with each other. At this depth, both of its walls descend, with an easterly underlie, at an angle varying from forty to sixty degrees. Upwards, from an average depth of five hundred feet, the western wall rises to the surface with the same inclination ; whilst the eastern assumes a vertical position, and subsequently turns off with a westerly dip. The vein consequently expands towards the surface in the shape of a funnel, as shown in Fig. 39, which represents, on a scale of 240 feet to one inch, a section made by Messrs. James and Stretch, Mining Engineers of Virginia, through the Chollar and Potosi shafts. This increase in volume is especially produced by the intervention, between the vein-matter, of large masses of country rock, detached from the walls, but which have usually moved a short distance only downward, by sliding from their original positions. The number and bulk of these horses increase towards the surface, where some of them have a length of nearly a thousand feet, and in many cases a width of above a hundred. The vein-matter filling up the spaces between these intervening masses of country rock is generally, near the surface, far inferior in width to that of the horses lying between it. The width of SILVER MINES OF NORTH AMERICA. 291 _ the mineral belt in which these branches come to the surface, and there form a scattered outcrop, is usually above five hundred feet. ~The Comstock lode is, on the western side, accompanied by a number of smaller veins, the outcroppings being visible on the surface, and some of which appear to be of considerable size. The western ={CHOLLAR SHAFT POTOSI SHAFT === = Ki Hl i A i iy ne i mf ‘ ue by = a = —<—~73=j = Ee 7 = = » —- of iE == A =O =< = au —— > | H Secrion oF Comstock VEIN. (Looking North.) boundary of the main vein is defined by a continuous clay selvage, or flucan, lying on the smooth foot wall, and separating the vein-matter from the country. On the eastern sides, the adjoining country rock is impregnated with matter similar to that composing the vein itself; and consequently, the well-defined east wall has often not sreniials the same relative position with regard to the entire vein, and, by U2 292 SILVER. cutting through what appears to be the east wall, another or succession © of others of a similar character are discovered beyond it. The enclosing rocks which accompany this vein vary somewhat in different portions of its course, although on the eastern side they invariably consist of slightly-differing varieties of propylite, or com- pact porphyry. On the western wall, the composition of the country presents greater differences. From the Best and Belcher Mine to Gold Hill, it is formed of syenite, which is, in some places, separated from the selvage of the vein by a fine-grained crystalline rock, of a black colour, partaking of the nature of aphanite, but of which the mode of occurrence is at present obscure. The outcrops of the Com- stock vein do not form one continuous line, but. rather consist of detached parallel ranges of brownish quartz, ordinarily protruding above the surface of the ground, and sometimes forming bold crests, which in the aggregate constitute a broad, interrupted belt. The porous nature of this quartz, originating from the decomposition and removal of fine particles of disseminated ore, and its brown colour, caused by the presence of metallic oxides, indicate the ore-bearing character of the vein in depth. A minute examination also reveals the occurrence of finely-disseminated metallic gold and silver, and occasional spots of the chloride and sulphides of the latter metal. The vein-matter of the Comstock lode is exceedingly varied in its character ; its chief constituents being fragments of the enclosing rock, clay and clayey matter, quartz, sulphide of silver, and other minerals. The shape and extent of the fragments of country rock are very various. They are, however, generally of a lenticular form, and differ in their dimensions from large “horses” down to the smallest brec- ciated fragments. Clay forms, in continuous sheets from north to south, the eastern and western selvages, which are sometimes from ten to twenty feet in thickness. Other sheets of this substance divide the horses from quartz, or the different bodies of quartz from each other; and where the vein-matter is so thin that the two clay bands come nearly together, the selvages have often a united width of from fifty to sixty feet. - The quartz of the Comstock lode is very rarely solid, and conse- quently its removal seldom requires the intervention of gunpowder ; it is usually much fractured, and in many places the effects of mechanical or chemical action are so great as to give it the appearance of crushed sugar. It almost always occurs in this condition when enclosed be- tween two clay walls, and in the immediate vicinity of rich masses of SILVER MINES OF NORTH AMERICA, 293 ore, The principal silver ores are stephanite, vitreous silver, native silver, ruby silver, horn silver, and polybasite, with which are asso- ciated small quantities of exceedingly rich argentiferous galena, Besides these are found native gold, iron and copper pyrites, blende, and car- bonate and phosphate of lead; the two latter only occurring in very minute quantities. These ores are seldom crystallised ; and conse- quently, specimens which would in other mining districts attract no attention, are regarded in Virginia as great curiosities. Quartz is, in reality, the only gangue of the Comstock vein. Carbonate of lime but seldom accompanies it, whilst the other carbonates are of exceedingly rare occurrence. Sulphates abound in the waters issuing from the mines, but the only one forming an essential constituent of the vein is gypsum, which is sometimes found in large crystals.* Sulphate of baryta has never been observed, and small specimens of stilbite and chabasite are only met with in the northern portion of the vein. The ore is differently distributed in the northern and southern por- tion of the lode, the passage between the two methods of occurrence being very gradual. In the northern part, the ore is concentrated in elongated lenticular masses, of which the greater axis is nearly ver- * An examination of the water issuing from the Comstock vein, in the Ophir Mine, January 12th, 1865, afforded Mr. G. Attwood the following results :— Heat of water, 70° Fahr., the air near being 62° Fahr. ; in Seventh Gallery, 25 feet below where water was taken, and 400 feet below the surface, it was 48° Fahr. Flow of water estimated at from 150 to 200 gallons per minute ; the total amount of water taken from mine being 300 gallons per minute. One imperial gallon contained 14°84 grains of mechanically suspended matter. Both water and suspended matter were apparently free from any trace of the precious metals. Specific gravity at 60° Fahr., 1:0007. Carbonic Acid in an imperial gallon, 23°30 grains, Fixed Matter e a. “ 23°02. 45 Composition of Fixed Matter. PEREOOTACG OF AIG Me ies ae fa ae ee galas beeen Ath) es DIREUOSa Oe gira le aeons Sen x sh tay ee Sulphate OL -Linie Gin 91 ee , e LOO! a Potassacg i toe bare see eae es | ow, ee SOE f MA gTICB Ri. wes tik Lit ered har itt DOR a ela iia ae A hl pain Shas, a i Se ny MURTIENU OL SOI? co oie oe oe er a ee ek Be minorideot Sodnim see ee TOGO me ecrny rirees Ue ea bps Coeg eds ae Wate doen one rdee eC CRC aaa Yau oh Rg As Sel aia aie led sh a gs os DOK) 97°80 294 SILVER, tical, but dips towards the south, and sometimes also to the east, their width varying from fifteen to fifty feet. In some cases, several of these adjoin each other in such a way that the most westerly one ex- _ tends further north than the one situated next to it towards the east, and this again further than its next eastern neighbour. The great value of the mines on the southern portion of the vein consists in the continuous character of the ore-bearing ground, which extends for an uninterrupted distance of above fifteen hundred feet. The vein is by no means productive throughout its entire width, but the ore is eon- centrated in continuous sheets, the principal of which is very near to, and parallel with, the eastern wall. Its widest places have a thick- ness of about fifty feet ; it generally commences at a depth of from one hundred and fifty to two hundred and fifty feet from the surface, and is at many points still worked in the lowest levels of the mines. Besides this very extensive eastern budy of ore, there is another in the Gold Hill Mines, further to the west, which extends from the outerop down to a depth of two hundred and fifty feet. A similar body has been worked in the Yellow Jacket, Crown Point, and Belcher Mines, and was remarkable from its southern portion being very rich in gold. It is, however, a well known fact, that the richness of the ores from the Comstock vein has in general diminished, although the total yield of the district has been more than kept up by the larger amounts which are now daily passed through the mills. When the vein was first opened, ores affording from one to seven hundred dollars to the ton were of frequent occurrence, and considerable shipments were made of parcels yielding from two to three thousand dollars per ton. Such ores are now but rarely met with, and the general average yield of all those treated will probably not much exceed thirty dollars to the ton. The cost of extraction has, however, been greatly reduced, and the methods of reduction much improved; and therefore ores which formerly could not have been treated with advantage now afford highly remunerative returns. The aggregate amount of ore now daily extracted from the Comstock vein is about twelve hundred and fifty tons. During the early period of the workings on the Comstock vein, the relative proportions of gold and silver yielded by the ores were found to change as a greater depth was obtained, the yield of gold being greatest near the outcrops, and gradually diminishing in the deeper portions of the lode. Recently, however, the proportion of gold has again been on the increase, and this is found to be the case, not in SILVER MINES OF NORTH AMERICA. 295 any one particular mine only, but throughout the whole extent of the lode.* The various phenomena connected with the occurrence of silver ore in the Comstock vein have been summarised by Richthofen as follows: Tt — 1st. The ore is, in. the northern part of the vein, concentrated in chimneys dipping to the south ; in the southern part it forms con- tinuous sheets of great length, but which are comparatively narrow. 2nd. These deposits of ore are enclosed in the eastern, and some- times also in the middle portions of the vein; the western branches are either barren or poor. 3rd. The richest and largest deposits have been found at those places where the outcrops, including those of the western branches, were most prominent. | Ath. In the northern part the vein is, at the levels explored, in- variably poor where it passes a ravine; but in the southern part the ore continues in the ravines. 5th. The richest portions of the lode are south of each ravine crossed by the vein. 6th. All the chimneys in the northern part are at those places where the walls, after close contact, rapidly diverge, and cause the vein to expand. — * The following assays from parcels of crushed ores worked in barrels, by Mr. }. Attwood, show the relative proportions of gold and silver in the rock from the Comstock Mines :— Second Class ore from the Ophir Mine, June 16th, 1863. Silver, perton . . . . 71°920z . . . $93°49 Gold + Ny Oe: FE re ae ae oa SASS Value... .$]5b15 Second Class ore from the Gould and Curry Mine, May 12th, 1864. Silver, perton . . . . 81'160z . . .$105°50 Gold Ree i Mice ee wk te te A Value . . .$158°20 Second Class ore from the Savage Mine, May 12th, 1865. Silver, perton . . . . 76180z . . .« $99°03 Gold ss bat hdres KEOUE steutit rul ck Senet Value . . .$131°48 + “The Comstock Lode, its Character, and the probable Mode of its Continuance in Depth,” by Ferdinand, Baron Richthofen. San Francisco, 1866. 296 SILVER, 7th, All the principal accumulations of ore are at those places where there was most room in the fissure for the deposition of quartz, and they are therefore generally rare where an unusual number of horses obstruct the vein. The first discovery of silver in Nevada appears to have been made in 1857, by two brothers of the name of Grosh, in a quartz vein now held by the Kossuth Gold and Silver Mining Company, on which they had a claim, Shortly after the discovery, oue of the brothers acci- dentally wounded himself with a pick, from the effects of which he died ; and the other brother went to California, where he died early in 1858, which probably prevented the valuable nature of their discovery from becoming generally known. In the meantime, placer mining was carried on to a considerable extent in various localities, principally in Gold Canon. In 1857, a man named Kirby, and others, commenced placer mining in Six Mile Canon, about half a mile below where the Ophir works now stand, and worked at intervals with indifferent success until 1859. On the 22d of February, 1858, the first quartz claim was located in the Virginia Mining District, on the “ Virginia Croppings,” by James Finney, generally known as “Old Virginia,” from whom the city of Virginia takes its name. This may be con- sidered the first location of the Comstock lode. The discovery of rich deposits of silver ore was not made until June 1859, when Peter O'Reilly and Patrick McLaughlin, while engaged in gold washing, on what is now the ground of the Ophir Mining Company, and near the south line of the Mexican claim, uncovered a rich vein of sulphide of silver in an excavation made for the purpose of collecting water to use in their rockers in washing for gold. This discovery being on ground claimed at the time by Kirby and others, Comstock was employed to purchase it, and Comstock’s name has thus been given to this great lode. From this discovery has resulted the almost miraculous growth of the district. Claims were at once taken up on the vein for miles in extent ; an unparalleled excitement followed, and miners and specu- lators rapidly congregated in the hope of obtaining a share of the re- ported wealth, while prospectors were busily examining almost every part of the country in search of silver ores. The following table, from the report of the State Mineralogist for 1866, gives the names of the various mining claims on the Comstock lode, as far as its continuity has been ascertained ; also, the length of the individual claims, length of each claim explored, percentage of SILVER MINES OF NORTH AMERICA. explored and unexplored ground, other information.* BOREL tn ey ae ior) a a Sierra Nevada . eens Unions: <¢ «s+ « + » Ophir North Mine . Mexreanes ss: Ophir South Mine KGOnbHIee se Sees 3 os California . Central, No.2. . Lah. Ce White and Murphy . STOR, 2 i. orn Best and Belcher . Gould and Curry . Savage, Old Shaft is CUTS.) Hale and Norcross Chollar Potosi . Bullion : Exchequer .. .» CAT a pee ai ss. Bs Apple and Bates . Imperial Alta . BaConie tae +8 | s Empire North Mine . Eclipse Sr Preneny, 3.7 esis” Empire South Mine . Plato: : 5: Bowers PUEDE ew eh es aes Winters and Kiistel . Consolidated Rice Ground .. . Imperial, H. and L. . Challenge noe @onmdenees .... .. = Burke and Hamilton Yellow Jacket . Kentuck. -3-'s Crown Point FGLONOT ae ec ete, ef Segregated Belcher . . COVENMIAING >) eels) fe North American . . Baltimore American . Length of Claim in feet. Length explored in feet. 297 depth of the lowest workings, and = rd : ales [3.8 of2| 85 |288 Qe2/ °F, |\esH REMARKS, ~Ooe| 8K |e es oe fea te ise = feet 30 70 260 Engine removed; not working. 32 68 200 Not working. 25 75 650 1 99 80 Explored by tunnel ; not working. 334 662 ) ( Explored through 100 Sos 549 Ophir, ‘‘ Mexican 100 \ Shaft.” 100 620 100 428 Explored by tunnel and winzes. Explored by whim on 100 nee 369 | White & Murphy’s 10 90 369 claim, and by the 100 ee 369 \ Latrobe tunnel; not working. 40 60 500 Not working. 100 fe 469 Engine removed; not working. 100 ao 900 100 oes 614 eRe aa 448 100 ane 783 50 50 923 47 53 803 Sp 100 540 100 «us 680 100 * 100 * 100 *e 100 os 100 ‘s a 100 ooo 2 100 ~ | | ca 100 3 100 ak ae 100 a op 100 ; S 100 & 100 <4 100 100 | 100 100 ae J 100 51 560 100 ase 460 100 pa 400 100 eee 850 100 ase 500 60 40 yale ‘ aia SRE 300 Not working, 25 75 300 Not working. North of the Utah, locations have been made on what is supposed to be the Comstock lode, but the developments are unimportant; the same remark applies to that portion of the vein south of the Overman. As far as is at present known, these two claims limit the productive portions of the vein, and include a length of nearly four miles. * This table commences with the claim on the extreme north of the vein. 298 SILVER. - The length given as belonging to the Best and Belcher, and Gould and Curry Companies, is the amount of ground claimed by each. The actual length of ground between the Sides and the Savage Companies, is only one thousand one hundred and forty-three feet. The lengths given for the Hale and Norcross, and Savage Companies, are measured on the croppings. Owing to the divergence of the north line of the Savage and south line of the Hale and Norcross, to the eastward, and the direction in which the vein dips, the length of their claims on the lode, in depth, is constantly increasing. Six feet of ground is in dispute between the Apple and Bates, and Imperial Companies. There are consumed annually by the Virginia Conipanies about 22,650 cords of wood, at an expense of $16 per cord, and a total cost of more than one-third of a million of dollars, and they also use about 15,504,120 feet (board measure) of timber and scantling, all of which must be transported long distances in wagons, at a cost of about $40 per thousand feet. Thus, for wood and timber alone the total annual expenditure is at least one million of dollars. Work commenced in earnest upon the Comstock lode about five years since, and its total yield has been about $65,000,000. The following was the production of the Gould and Curry Mine from the incorporation of the Company in June 1860, to Nov. 30th, 1866 :-— DATES. \Ore worked, &c. | Bullion, &e. ge ie | Tons. | Per Ton. From July 1, 1860 to Dec. 13, 1860 1403 $22,004°82 $156°62 7 ec 14, -y 24; Deesta eel 300 4422144 | 147-40 » Dec.14,1861 ,, Nov.30, 1862 8.4424 842,538°80 99°80 , Dec. 1, 1862,, Nov.30,1863 | 48,745 3,902,912°64 80°07 ,, Dec. 1, 1863,, Nov. 30,1864 | 66,4773 4,798,124'90 72°18 ,, Dec. 1, 1864,, Nov.30,1865 | 46,0223 2,026,172°57 44-02 , Dec. 1, 1865 ,, Nov. 30,1866 | 60,4174 1,690,952°25 28:00 PIMC Potts) cs ss Nae ad ae teat en ca ee i | 13,326,927°42 roid Taalings fe eh in 300, 143°76 Worked, Toms «. ...°. . 230,546 | $13,627,07118 | $59-02 On hand, December Ist, 1866 . . . 4,249% tons. otal Produce ee wesc A a EN oom 5, ’ SILVER MINES OF NORTH AMERICA. 299 It has been estimated that five or six other Companies have taken out more than a million dollars each, and about twenty have each taken out small sums. Richthofen estimates the total yield of the Comstock vein, up to the end of 1865, as follows; thus making the produce of silver from this source during three years, equal to about 23 per cent. of the whole production of the world during that period :— The quantity of ore hoisted during the quarter ending 30th Sep- tember, 1865, was 71,000 tons, or about 284,000 tons per annum, but this was considerably exceeded in 1866.* Year. Total. Silver. Gold. 1862 . . . about $ 4,000,000 about $ 2,500,000 about $1,500,000 i ae » 12,000,000 ,, 8,000,000 ,, 4,000,000 1864 16,000,000 ,, —- 11,000,000 ,, 5,000,000 1865 » 16,000,000 ,, 11,250,000 ,, —-4,750,000 Total produce 1862 to 1865 $48,000,000 $32,750,000 $15,250,000 The aggregate amount of water daily pumped from the several mines cannot be ascertained, since no record has, in most instances, been kept. Nearly every mine has its pump, which is in most instances idle during a large portion of the twenty-four hours, but in the deeper mines it is kept constantly working. The Best and Belcher, and Hale and Norcross, each, during some part of the summer of 1865, pumped 15,000 gallons of water per hour. The Gould and Curry has a pumping capacity of 25,000 gallons per hour. The chief difficulties attending the working of the Comstock vein are occasioned by its immense width, and the friable and clayey nature of its constituents. In order, therefore, to be enabled to remove the ore, and at the same time keep open the necessary work- ings, the whole width of the lode has to be timbered with rectangular beams of pine, generally 10 in. x 12 in., which are put together in hays, about eight feet from centre to centre, in which the vertical supports stand perpendicularly over each other, from bottom to top, whilst the cap-pieces of one set, which form the foot-pieces of the next, extend across the vein from one wall to the other. The spaces between the timbers are filled in with attle when no longer required to be kept open for mining purposes or ventilation. The expansive force of the * Tons of 2,000 lbs. each. + The American gallon is equal to 08331] imperial gallon. 300 SILVER. clay selvages is, however, under the influence of moisture, exceedingly great ; and itis by no means uncommon, in wet situations, to see heavy: beams, 12 in.x14 in., broken like match-wood, or bent so as to obstruct the levels. The subdivision of the Comstock vein into a large number of claims of very limited extent, has been productive of much unavoidable expense ; occasioned not only by the multiplicity of shafts and the extra amount of machinery thereby rendered necessary, but also further augmented by the additional expense of greatly-divided management, and a series of ruinous and vexatious lawsuits, due to disputed claims and alleged encroachment of rights. In order to relieve the various mines on the Comstock lode frais the constantly increasing expenses of drainage and of hoisting the ores to the surface, it has been recently proposed to bring in a deep adit, sufficiently wide for a double line of railway, from the Webber Cafion, a distance of nearly four miles. This proposed gallery, which is known as the “Sutro Tunnel,” would intersect the lode at a depth of one thousand nine hundred feet below its outcrop ; and besides effect- ing the drainage of all the mines to that level, would cross-cut several veins in its course, and afford means of transport for the ores to Carson River, where water-power can be obtained, and wood procured at a comparatively cheap rate. Intervening cafions, about three- quarters of a mile apart, afford facilities for sinking four different shafts ~ to the level of the proposed tunnel, and from these the work would be extended in both directions, as well as from its mouth in the Carson valley. These shafts would respectively require to be sunk to the following depths, viz, 443, 980, 1,360, and 1,436 feet; the cost of the tunnel is estimated at $1,983,616. It is calculated that under favourable circumstances this great level could be completed within three and a half years after its commencement ; but, although the rock through which it would have to be driven is, ¢ ne speaking, of a not unfavourable character for the prosecution of such work, it is more than probable that a considerably extended time would be required for its execution. A franchise has also been granted to a company to construct a railway from Virginia to the Truckee River, with a branch from thence to Carson city. The length of the road from Virginia to the Truckee will be forty-five miles, and its maximum gradient seventy-two feet per mile. This road, complete and ready for traffic, including rolling stock, is estimated to cost $3,774,000, whilst it is stated that its gross income would exceed $2,000,000. With the exception of kos on the Comstock vein, some of the SILVER MINES OF NORTH AMERICA. 301 most important mines of Nevada are comprehended within what is known as the Reese River Mining Region, for much important information relative to which, we are indebted to voluminous notes furnished us by Mr. A. Blatehly, Mining Engineer, of Austin, who has devoted much time and attention to the study of the mineral deposits of that portion of the State in which he resides. Resse River Miniwe Recton.—The extensive mineral country known as the Reese River Mining Region, is situated in a great mineral belt which extends three hundred miles north and south, by two hundred and fifty east and west, and comprises the whole north-eastern portion of the State of Nevada. The face of this plateau, which is elevated about five thousand feet above the level of the sea, is covered by broken and detached ranges of mountains, whose highest peaks rise to an altitude of ten thousand feet. Owing to the broken nature of these ranges, the valleys lying between them are connected with one another by low passes, generally forming good natural roads, and furnishing easy grades for the construction of railways. Although numerous streams rise in the mountains, some of sufficient volume for driving mills, yet they all sink and disappear on reaching the sandy valleys below. North-west of this region hes the Humboldt valley, which contains a large amount of arable Jand. On the hills and mountains a small variety of pine grows abun- dantly, but the valleys are entirely destitute of timber, and only covered with sand and a small shrub known as “sage brush.” Many of them, in close proximity to the mines, contain vast deposits of nearly pure salt, and, consequently, the price of this substance may be considered as merely nominal throughout the whole country. This district lies between longitude one hundred and fourteen and one hundred and eighteen degrees west, and latitude thirty-seven and forty-one degrees north. At some period, generally subsequent to the cretaceous epoch, igneous agencies have been active, and probably three-fifths of the whole country are covered with rocks of volcanic origin. The other portions of the surface, where exposed, are composed of granite, syenite, gneiss, slate, and limestone; the two latter being frequently fossilife- rous. ‘Triassic fossils occur in many localities, and have been clearly identified ; others much older, probably Silurian, have been found near Austin. The country has, however, been too recently discovered to admit of any but imperfect geological explorations. The great majority SOG? SILVER. of the metalliferous veins are in granite, syenite, and slate ; the lime- stone enclosing but comparatively few. Nearly all of the valuable metals are found in this region, such as gold, silver, copper, lead, iron, zinc, antimony, &c. At present, owing to the high price of transport, gold and silver mines are the only ones that can yield profitable results. | . Reese River District—This district is situated on the western slope of the Toiyabe range of mountains, which extends north and south for the distance of one hundred miles, and occupies nearly the geo- graphical centre of the State of Nevada. A number of subordinate districts are situated on this range, and the majority of the mines worked in the country are found on its eastern and western slopes. In this region silver was first discovered, and here the mines have been more fully opened, and a greater number of mills erected, than in any other locality. Austin, the largest town in this part of the country, containing three or four thousand inhabitants, is built in the centre of the district. Nearly all the ores met with, at the surface, consist of chloride, iodide, and bromide of silver associated with native silver ; whilst below the water level, ruby silver, stephanite, poly basite, antimonial silver, argentiferous galena, silver fahlerz, xanthocone, &e., besides a great variety of combinations more interesting to the mine- ralogist than valuable to the miner are found. The first attempts at working these ores were unsuccessful ; but since the introduction into the country of the process of roasting with salt in reverberatory furnaces, the results obtained have been satisfac- tory, although dry crushing and working the furnaces by hand render the process very costly in a country where labour costs at least four dollars per day. Sixty dollars per ton of 2,000 Ibs. is the rate now charged at the custom malls, a return of eighty per cent. of the fire assay of the ore being guaranteed. This district, though small in extent, six miles north and south, by one and a half east and west, contains a remarkably large number of silver-bearing veins. Over five thousand different branches have been discovered and recorded in the district, nearly all of which are visible at the surface ; and ninety-five per cent. of this number contain silver, though frequently not in paying quantities. The vein-systems are remarkably numerous, besides which a complicated series of faults renders their study interesting. Six apparently distinct systems have been observed, and the relative ages of four of them satisfactorily determined. The oldest and by far the most numerous veins have a oe eas SILVER MINES OF NORTH AMERICA. 305 strike north-west and south-east, magnetic, the variation being sixteen degrees east, with a dip of forty-five degrees to the north-east; many of the richest veins belong to this system. The second system has a strike north seventy degrees west, and south seventy degrees east, with a dip of fifty degrees to the north. The third system has a strike of north twenty-five degrees west, with a dip of seventy degrees to the west. These three systems have all well-defined walls, accompanied by slickensides and flucan. The veins of the fourth system strike north and south, and stand perpendicularly. Two other systems are believed to exist, one with a strike east and west, and a dip of forty degrees to the north; the other running north-west and south-east, and dipping thirty degrees to the south-west; the relative ages of these have not been determined. The mineral belt extends the whole length of the district, by nearly two miles in width. All of the richest mines are in this belt, which runs nearly parallel with the Toiyabe mountains. Owing to the recent discovery of these mines, and the disadvantages incident to new countries, no deep or extensive explorations have yet been made ; about four hundred feet being the greatest depth yet attained by any incline following the dip of the veins. Many of the mining operations have been conducted with a very moderate degree of skill, and are consequently of little value. The following description em- braces a few characteristic mines on each well-established system of veins, commencing with the oldest. First System.—The Oregon, like all the veins of this system, has a strike north-west and south-east, and a dip of forty-five degrees to the north-east ; its average thickness is about one foot. This was one of the first veins opened in the country, and has yielded a considerable amount of ore ; the average produce of the rock worked has been over a hundred dollars per ton. An incline has been sunk to the depth of four hundred feet, and drifts run, on each side, for over a hundred feet. This vein was irregular and broken near the surface, but for the last hundred feet appears to be more regular. It contains the ores usually found in the district, such as chloride of silver, ruby silver, and stephanite, associated with large quantities of manganese. North Star.—This mine has been opened to the depth of three hundred and forty feet, and drifts driven to the eastward for two hundred feet. Its average thickness is about eighteen inches, though in some portions it is three feet in width: the composition and yield of the ores are similar to those of the Oregon. Revenue.—The thickness of this vein between the walls is two feet; the ore is found in streaks of from three to ten inches. The ores in this vein are rich, the yield by assay of the pure mineral having been over five hundred dollars per ton, whilst the yield by working in the mill has not been above two hundred. Larger 304 SILVER. pieces of native silver have been taken from this mine than from any other on Reese River. North River.—This vein, so far as it has been followed down, has increased in thickness; at the surface it was only six inches wide, but at the depth of a hundred feet it is over a foot in thickness, and in some portions even eighteen inches. The ore in this mine resembles that of the Revenue. The yield of the ore worked has been about two hundred dollars per ton ; nearly all of the veins of this system are double, consisting of two or more foliations, usually from two to four feet apart. Guconp SystEM.—The strike of these veins is north seventy-five west, and south seventy-five east, and the dip fifty to the north. These veins are usually large ; from two to eight feet thick. Whitlatch Union.—This is one of the largest veins in the district, being from four to eight feet thick ; it has been opened to the depth of a hundred and twelve feet, and drifts driven on each side for one hundred feet. The ores so far found belong to the surface class, and their yield has been about a hundred dollars per ton. This vein was divided by a fault, and much labour expended before its continuation was again found. Savage.—This mine has been more fully opened than any other in the district, and hence it has produced more ore. An incline has been sunk to the depth of three hundred feet, and two levels opened ; the lower one for a distance of six hundred feet, and the upper for about four hundred. The ores are antimonial with small amounts of ruby silver. Tuinp System.—The strike of these veins is north twenty-five degrees west, and south twenty-five east, and their dip seventy degrees to the westward. All their ore is cased in greenstone with a large amount of clay, and they usually carry a considerable body of water. The ore is not so generally diffused throughout the veins as in the two older systems, but is found in separate deposits, and the thickness of the vein is not so regular. Whitlatch Yankee Blade—The thickness of this vein is from two to four feet ; it has been opened to the depth of three hundred feet, and drifts driven to the distance of seventy feet, The ores are similar to those of the older systems, except that they contain larger amounts of arsenic ; the average yield has been about a hundred dollars, though a number of tons have produced three hundred dollars per ton. The Confidence is almost a fac-simile of the Whitlatch Yankee Blade. Fourtu System.—These veins strike north and south, and stand perpendicularly ; they are less metalliferous than those of the older systems, and are more spotted, many portions being entirely barren. They all, however, contain gold in sufficient amounts to constitute a portion of the total value of the ore. So far as is known, this is the latest, or one of the latest of the known systems in the country ; con- sequently it has been less disturbed by faults than any other. One of the veins, which has been opened to the depth of a hundred feet, has a thickness of about two feet. The average yield of its ores is not known, but some samples have afforded by assay a hundred and fifty dollars per ton. The average yield of the sulphides taken from below the water level, was nearly double that of surface ores. Amador District-—This district adjoins that of Reese River on the north, and is on the same mineral belt. The country rock is slate, and the veins, though large, are not so rich or numerous as In Reese River. SILVER MINES OF NORTH AMERICA. 305 No veins have been found passing from the granite into the slate, and none between the two formations. The usual strike is north-west and south-east, and the dip about forty degrees to the north-east, Many of the veins show evidence of great dynamic action, their walls being often polished as smooth as glass. ‘The Amador, Rough and Ready, and Corral Mines have been opened to depths varying from two to four hundred feet ; the average thickness of the veins being from four to six feet. These veins are capable of producing a large amount of ore, but, so far, have not proved sufficiently rich to leave a profit to the mine-owners after paying sixty dollars per ton for reduction, favenswood District—This district lies about eighteen miles north- west from Austin; the country rock is slate, and the veins are very numerous and rich in copper and lead, but rarely yield over forty dollars per ton in silver, which will not, at the present scale of charges, pay the expenses of working. Cortez District—Cortez is sixty miles north of Austin, and but a short distance from the Humboldt River. Wood, water, and grass are comparatively abundant; the country rock is slate, granite, and limestone. There are many known veins in this district, the principal being the Nevada Giant. Nevada Giant.—This crops to the surface for the distance of two and a half miles, its thickness being from fifty to two hundred feet, with a direction nearly north and south, and dipping to the east. The vein contains many deposits or chimneys shgwing at the surface large quantities of valuable ore, which principally consists of disseminated stephanite. | Washington District—Forty miles south of Austin is Washington, which contains a large number of veins, yielding argentiferous galena : they are generally rich in lead, and assay from twenty to sixty ounces of silver to the ton of ore; the country rock is slate and limestone. Union District.—This district is sixty miles south-west from Austin on the western slope of the Shoshone range of mountains, which are generally well covered with wood. The enclosing rock is syenite, the veins are small, rich, and numerous ; in the slate they are larger, less productive, and fewer in number, while the value of the few found in limestone has been in no way determined. Only one vein in this district has been opened below the water level, and in that, sulphide of silver was found. Hence all the ores worked in this neighbourhood have been chlorides, The general direction is north-west and south- east, with a dip of forty degrees to the north-east. x 306 SILVER. The Pleiades.—This mine has been opened to the depth of two hundred feet, and drifts driven on each side for a distance of seventy or eighty feet ; the thickness of © the vein varies from two to four feet; the ores are similar to those found near Austin, but contain rather more lead; their average yield has been nearly one hundred dollars per ton. There are many other similar veins in the district, such as the Clipper, Idaho, Shaw, Silver Moon, &c.; some being rich in gold, as the Franklin and Shamrock. The Great Eastern.—The strike of this vein is north and south, with a dip of about sixty degrees to the west. It is composed of a number of different bands, varying from ten to one hundred feet in thickness, with an aggregate width of from three to four hundred feet. It crops to the surface for a distance of over ten miles, and passes through different country rocks, such as slate, limestone, and porphyry, but it is only productive in the latter. In the Great Eastern claim a tunnel has been run through two of the strata, one thirty-five feet thick, and the other about ten. The larger stratum, cut by the tunnel, afforded assays of forty dollars per ton ; the smaller one yielded some samples producing a hundred dollars per ton. Smoky Valley District is situated seven miles south-east from Austin, on the eastern slope of the Toiyabe range of mountains ; the country rock is slate and granite; many small rich veins are found in the granite, but the principal lodes are in the slate. Those which have a direction east and west, and a dip of about forty degrees north, are known as the Mammoth and Smoky Valley, have a thiek- ness of from twenty to forty feet, and run parallel, about one hundred yards apart, for a distance of over three miles. An incline has been sunk on the Smoky Valley, to the depth of two hundred feet, but the average yleld has not yet been determined. The Twin River District is situated on the eastern slope of the Toiyabe mountains, about fifty miles south from Austin ; the country rock is slate and granite; all of the valuable veins are found in the slate, or at the point of junction of the slate and granite. They are large and numerous, many of them having a thickness of from twenty to forty feet; their general direction is nearly north and south, with a dip of seventy degrees to the west. The Murphy is the only vein that has been opened and worked sufficiently to prove its value ; it is twenty feet thick, with a paying streak of from five to seven feet in thickness. Many other veins are of equal or greater size, and present equally favourable indications. The Vanderbilt is nearly seventy feet in thickness, with a foot wall of granite, and a hanging wall of slate, and can be traced on the surface for a distance of over a mile. The ravines cut the veins at right angles, to the depth of nearly two thousand feet ; thus affording great facilities for opening mines by means of adits driven into the vein on its direction. This district has been recently discovered, but bids fair to become an important one ; wood, water, and salt are abundant. SILVER MINES OF NORTH AMERICA. 307 Mammoth District is seventy miles south-west from Austin ; the veins in this locality are very numerous, regular, and uniform in direction, dip, and thickness ; being but little disturbed by faults. Their general strike is north-west and south-east, and their dip forty degrees to the north-east ; the average thickness is about two feet. None of the veins have been opened to any considerable depth, and all the ores, so far worked, have been from the surface. A large amount of ore can be taken from the backs, that will yield about forty dollars per ton. This district has not been discovered sufficiently long to admit of any but superficial openings being made, but it promises to become an important mining country. San Antonio District—This district is situated about a hundred miles south from Austin. It is an almost perfect counterpart of the Reese River district. The vein systems are equally numerous, but their relative ages have not been ascertained. The surface ores have the same composition, and are of about equal richness, although the veins are larger; the country rock is generally slate. No water is found within a mile and a half of the mines, and then only in small quan- tities; nine miles from the mines, water is met with in sufticient abundance to supply a mill, and wood can be procured within six miles of the water. The Liberty.—This mine has been opened to the depth of two hundred and fifty feet without finding water. The thickness of the vein is from four to eight feet ; the run is west-north-west and east-south-east, and the dip forty-two degrees to the north. So far as yet opened on, the ores are chlorides and iodides; more horn silver is found in this mine than in any other in the country. The yield of the ores, selected for working, has been over three hundred dollars per ton. Las Anvmas.—This mine has not been opened as fully as the Liberty, which it very much resembles, only that the vein is thicker. Want of wood and water has greatly retarded the development of this district. Silver Peak is one hundred and forty miles south from Austin. A large amount of exfoliated ore, which has fallen from the backs of the veins, is found at the surface; some of these ores have been worked, and good results obtained: the country rock is granite, slate, and limestone. Salt is abundant, and wood and water moderately plentiful. In addition to the foregoing two great mining regions of Nevada, there are numerous others which are as yet of minor importance, but which are being steadily and rapidly developed. It would, however, be im- possible to enumerate even the names and positions of the different veins which have been discovered in this State. X 2 308 SILVER. Orner Mining Disrricrs—In Esmeralda County, where there are some important veins, there are three distinct hills in which the principal mines are situated. Silver Hill, in which are the Esmeralda ledge; the Winnemucca, Falls of the Clyde, St. Louis, Utah, Antelope, Red White and Blue, Cedar, Greenback, Lily of the West, Locomotive, and many others, on some of which, shafts have been sunk 300 feet, and rich ore taken out; about twenty levels have also been run into the hill, some of them from 500 to 600 feet in length: no water of any consequence has been met with. Middle Hill contains many promising veins, but sufficient work has not been done on them, to determine their true characters. Last Chance Hill, in which is the Wide West ledge, the Del Monte, Golden Age, Empire, Crocket, tna, and many others. Con- siderable amounts of the precious metals have been taken from them, but during the last twelve months the same amount of work has not been done on mines in this district, as in the previous year, owing to litigation and insecurity of title. In this district many hundreds of tons of boulders from the surface have been broken by miners and worked in the mills, generally paying well. Aurora is the county seat. During the past year, mines in the Bodie District, about twelve miles west from Aurora, have been worked with profitable results. Two large mills have been erected in the district, and are working ores which pay from $50 to $100 per ton. Montgomery, Blind Springs and Hot Springs Districts, about forty miles south-east from Aurora, have also been discovered within the last two years. Lake District, near Walker Lake, has also been recently discovered. Many large veins, with prominent croppings, are being worked, and some ore rich in both gold and silver has been taken out. Columbus, Silver Peak, Red Mountain, Cottonwood, and Minnesota Districts, about seventy-five miles south-east from Aurora, have also been dis- covered during the past two years. The veins are large and well defined, being from one to four feet wide, and can be traced for several hundred feet, the croppings being generally prominent. The Montezuma Mine, in Humboldt County, is situated in Trinity District, fifteen miles west of Unionville. The Montezuma ledge runs in an east and west direction, and dips north at an angle of seventy degrees. The principal country rock is a metamorphic slate. The vein is ten feet thick, well defined, and has a clay selvage oneach side. The ore principally consists of oxide of antimony, carbonate and oxide of lead, and arsenical pyrites. So far as yet explored, this vein contains but little. refuse. The ore yields, by mill process, without roasting, an average of seventy-five dollars of silver per ton. On this vein two shafts have been sunk, each thirty feet SILVER MINES OF NORTH AMERICA. < 309 in depth, and drifts have been extended to an aggregate length of eighty feet. The distance from the mine to the Humboldt River where at a moderate cost good water-power can be obtained, is four miles, over a good natural road. The work done, thus far, has been by way of exploration only. The Montana Mine is situated n the Sacramento District, eighteen miles south of Unionville. The lode is in slate and limestone. It runs north and south, and pitches west seventy degrees. The Sheba Mine is near Star City. Its ore principally consists of sulphide of antimony, brittle silver ore, and antimonial silver, and is found in deposits which are distributed irregularly through a stratified belt, or ore channel, about a hundred and fifty feet thick, which lies between quartzite and slate. In the development and working of this mine, three thousand feet of levels and drifts have been run at a cost of $75,000. The aggregate yield has been about $70,000 ; and the average produce per ton, $140. The De Soto Mine is situated immediately south of the Sheba. The vein is four feet thick, runs in a northerly direction, and has clay selvages and polished walls ; the country rock is slate. Upwards of a thousand feet of tunnel have been run. About two hundred tons of ore have been taken out, which averaged nearly $100. The ore closely resembles that of the Sheba. The Yosemite Mine is situated two miles south-east of Dun Glen. The formation in its vicinity is slate and limestone. The vein is two feet thick, and has clay selvages and striated polished walls. It runs north and south, and stands almost vertically ; a shaft has been sunk to the depth of fifty feet, and from this about fifty feet of drifts have been run. Three hundred feet of a working tunnel have also been run. Several small faults occur in the vein, which give it a broken appearance. The ore is a black sulphide of silver, containing a small proportion of carbonate of copper. It is exceedingly rich, some of it assaying as high as $13,000 per ton. The Gem of the Sierras is situated in Sierra District, five miles from Dun Glen, in a limestone formation. The vein is twenty inches in thickness, runs in an easterly and westerly direction, and dips 70° south. A considerable portion of the gangue is calcareous spar. The ore consists of sulphice and chloride of silver, mixed with a little carbonate of copper ; and the parcels worked have yielded at the rate of $175 per ton. The Tallulah Mine lies a mile and a half west of Dun Glen, and comprises several ledges running north and south, and dipping west. The enclosing rocks are slate, syenite, and porphyry. A level has been extended five hundred feet, cutting at an average depth of a hundred and eighty feet, a well-defined vein separated from the enclosing rock by selvages and polished walls. The ores chiefly consist of antimonia, sulphide of silver, with a little native metal, and after selection yield about $150 per ton. The Pride of the Mountain is sttuated in the Winnemucca District, twenty miles north of Dun Glen. The vein runs north and south, pitches east at an angle of 45°, and is about fourteen inches thick. It is well defined and continuous, and has clay selvages and striated walls. ‘The country rock consists of a soft metamorphic slate, and much of the gangive is calcareous. In making the incline, forty tons of ore were taken out which, without selection, yield $80 per ton by the pan process. | The Manitowoc Mine lies two miles south of Unionville, in Buena Vista District. The vein is two feet thick, runs north and south, and dips west at an angle of 45°. The country rock is slate. The ore consists of :ulphide of silver and xanthocone con- taining a small proportion of copper, and is easily worked by the common pan process. . 310 SILVER. Devil’s Gate District is situated in the north-west portion of Lyon County, and is the oldest district in it. The lodes in the most northerly portion are auriferous in their character, many being well defined. The most prominent veins, however, are the Wide West Twin, and Buckeye. Lying south are the Daney, and Charles Cany Companies. The Daney Company has erected permanent works, and ore has been met with in several places in the mine, but not sufficient in amount to keep in operation the ten-stamp mill which the Com- pany has erected. There are 34 mills in this county, principally employed in the reduction of ore from the Comstock vein. There are several veins in Nye County, which in the ageregate produced during the year 1865 about $100,000 worth of bullion; this principally consisted of silver yielding only a small proportion of gold. In Washoe County there are no mines worked to any extent, but it contains several reduction works, principally occupied in the amal- gamation of Comstock ores. According to the Report of the State Mineralogist, there are now in the State of Nevada no less than 116 distinct reduction works, pro- vided in the aggregate with above 2,200 stamp-heads. CHAPTER XV. CENTRAL AMERICA AND SOUTH AMERICA. GUATEMALA — MINES OF THE CENTRAL AMERICAN MINING COMPANY — MINING DISTRICT OF ALOTEPEC — PRODUCE OF SILVER—SOUTH AMERICA —MINES OF PERU—ANNUAL PRODUCTION OF SILVER—BOLIVIA—MINES OF POTOSI—THEIR PRODUCTION OF SILVER—-CHILI—MINES OF COQUIMBO—ANNUAL PRODUCTION OF CHILI—NEW GRANADA—SANTA ANA MINES—TABLE SHOWING PRODUCTION OF SILVER IN VARIOUS COUNTRIES. CENTRAL AMERICA—Comparatively little is known of the geology of this country, except that the predominating rocks are granite, gneiss, and mica slate, and that the abundance of igneous rock bears wit- ness to extensive volcanic action. Silver mines are situated in various parts of Central America, but the only ones of which we have any authentic information are the following :— Mines of the Central American Mining Company.— The mining district of Alotepec is situated in about 14° 40’ of north latitude, and 88° 58° of west longitude ; being a portion of the Department of Chiquimula in the Republic of Guatemala. The mountain of Alotepec forms part of the great chain which runs towards Honduras, in which the best silver veins of Central America are found. As a mining district it appears to have been known more than a hundred years ago, and a period of great prosperity occurred about seventy years since. The veins are found in porphyritic rocks, and occasionally pass into sandstones and limestones, which appear to have been uplifted by the porphyry. Their general direction is from east to west in the sandstone and limestone formations, and south-east and north-west in the porphyry. The mineral wealth of the district principally consists in silver, lead, and copper. The silver is found both with lead and copper ; also as a sulphide of silver, and in the state of chloride. Lead is found as sulphide and carbonate ; the copper is in the form of pyrites, green and blue carbonate, and as an oxide. There is also a great abundance of iron ore in different parts of the moun- tains. The rocks supply abundance of lime for mortar, building-stone of various kinds, clay for bricks and tiles, and an inferior kind of sand is found in the ravines. The firestone in the neighbourhood is not good, but it may be obtained from Tuitiapa, and fireclay at Esquipulas and near the city of Guatemala. The number of veins and mineral deposits in the mountains of Alotepec cannot oS SILVER. be less than thirty-eight or forty, which the late Mr. Floresi divided into tive groups or divisions, viz. :— . lst. The’mines of Don Manuel Midense. 2nd. Those of Don Cruz Duarte. 3rd. San José, San Rafael, and Santa Rita. 4th. Anderson’s Hope and El Tajo. 5th. Taylor’s Hope, &c. &c. &e. The first group comprises the mines of San Pantaleon, Santa Rosalia, Socorro, and Santa Fé. These mines are on the north side of the mountain, looking towards the Rio del Valle, and are surrounded by a fine forest, chiefly of pine and oak. The pasture land enclosed is sufficient for about 180 animals during the greater portion of the year. There is a supply of water sufficient for stamps, &c.; and about two and a half miles from the mines, is a piece of land called “La Vega de San José,” having the advantage of extensive water rights, and on which very convenient reduction works have been constructed ; the German barrel process being that adopted. Before their purchase by the present Company, the mines had been worked at different periods, but very unskilfully. The vein of San Pantaleon is that which has yielded the best produce. The veins of Santa Rosalia, Socorro, and Santa Fé have been worked at different times, and produced moderate quantities of ore of good ley. They are well situated for deep cross-cuts, and.can be worked and drained without the necessity of a shaft, requiring only such openings from the surface as may occasionally be wanted for ventilation. To the second group belong San Carlos, Rosario, San Miguel, San José de Atutilca, and other mines. The veins, although in general not very wide, are promising ; the ores are rather mixed, and principally consist of compounds of copper, lead, sulphur, and silver, generally better adapted for smelting than amalga- mation. The mines of this group are also well situated for adits, and are not more than a league from the Vega de San José. Jn the third group are the mines of San José, San Rafael, Santa Rita, and San Domingo. San Rafael and San José appear to have been worked extensively, but they do not present such facilities for deeper levels as the other mines. The fourth group comprises the mines of Santa Catalina or Anderson’s Hope, and El Tajo. Mr. Floresi considered them to be neither regular lodes, nor beds, but a reunion of several small veins. The ores of El Tajo form an excellent flux in the smelting of other ores. The fifth group consists of Taylor’s Hope and adjoining veins. Taylor’s Hope is about six miles from the reduction works. The rivers in the immediate neighbourhood of the mines allow of the reduction establishment being worked entirely by: water-power; the forests are capable of supplying charcoal and wood to any extent, and very few places can furnish a larger variety or a greater abundance of timber than this district. The silver produced by the Central American Mining Company has been chiefly obtained from the mine of San Pantaleon, but recently, considerable quantities have been raised at San Carlos. Of late years also, some ore has been extracted from San José de Atutilca. | It will be observed by reference to the annexed tabular statement that the pro- duction of these mines has considerably fallen off since 1863, but discoveries are expected to result from the exploratory works now in progress, and it is hoped that the returns for the present year may again increase. SOUTH AMERICA. 313 STATEMENT OF SILVER PRODUCED BY THE CENTRAL AMERICAN MINING CoMPANY, FROM 1858 To 1865.* OZ, ; OZ, 1858 Produce of oresold . . . 18,187°80 1859 e ‘ ae 62,623°45 1860 i a ae 67,825°95 1861 i f : 45,508°05 » Of bar silver sold . 80,579°94 ee SPS) 198 Oay-90 1862 » Oforesold . . . 34,662°45 » of bar silver sold . 21,686°19 4 . m 65,897°00 bis poke oe HET OD 945-64 1863 maeot oresold)~ 75.4.4: 4,955°25 » of barsilver sold . 12,795°84 a i Xs 109,446°29 2 127,197°38 1864 paOL OTS BOldy, ofa si % 2,923°95 » of bar silver sold . 64,762°96 : 67,686°91 1865 Ben Or ra.sOlds a. 1,768°20 ,, of bar. silversold . 27,354°58 ee eo Too 78 Tatal.produce . . . . +. 4s . 620,977°90 oz. Sourn .AMERICA—The silver mines of that portion of South America which constitutes the republics of Peru, Bolivia, and Chili, are next in importance to those of Mexico and Nevada, and would, had they been more favourably situated, probably be capable of affording a larger annual amount of silver than even the mines of Mexico. The great elevation of many of the argentiferous districts of South America is, however, a great drawback to their value, since nothing but the extreme richness, or the great abundance of the ores, could afford a sufficient inducement to undertake the working of mines in such desolate and inhospitable regions. Prrvu.—The mines of the Cerro de Pasco are the most celebrated of Peru; the principal ores worked being of the description known as pacos, which are analogous to the colorados of the Mexican miners, and consist of ferruginous earths containing varying amounts of silver. In order to form an idea of the enormous quantities of these argen- tiferous gossans, which nature has deposited in the calcareous hills of this district, it may be stated that the bed of silver-bearing oxide of * Furnished by Mr. J. Phillips. 314 SILVER. iron of Pasco or Yauricocha, had been worked, without interruption, since about the commencement of the seventeenth century ; and that although, during the first twenty years previous to the commencement of the nineteenth, they had produced above five million marks of silver, very few of the workings then penetrated to a depth of above a hundred feet below the surface. The metalliferous deposit of Yauricocha crops out on the surface for a length of 2,500 fathoms, and a width of 1,200 fathoms. M. de Rivero considers the pacos of Santa Rosa, one of the most productive mines in the district, to be a deposit and not a true vein, since they run parallel with the general formation of the country, and the gangues have no crystalline or drusy structure.* These mines were accidentally discovered by an Indian in 1630, and were, for a long period, regarded as the richest in any portion of the American continent. They have, however, been badly worked, and, many years since, one of them fell in upon the workmen, of whom three hundred were killed, from which circumstance the mine has acquired the name of Matagente, or “ Kill-people.” The town of Cerro de Pasco is 13,673 feet above the sea, and when the condition of the mines is prosperous, sometimes contains 18,000 inhabitants ; according to Tschudi, the two principal argentiferous veins of this district are the Veta de Colquirirca and the Veta de Pariarirca. The former of these runs in nearly a straight line from north to south, and has been traced for a length of 9,600, and over a breadth of above 400 feet. The second takes a direction from east-south-east to west- north-west, and is supposed to intersect the-other under the market- place of the city. Its known extent, in length, is 6,400 feet, and its width 380 feet. Steam-power was first introduced into these mines in 1814, by the celebrated Richard Trevithick, but the acid waters of the veins acted so rapidly on the pumps, that they were very quickly destroyed, and in 1832 only one of the engines remained at work. In addition to the district of Cerro de Pasco there are various others in Peru which have produced large quantities of silver. The principal of these are those of Caxamarca, Pataz, Huamanchuco, and Hualgayoc. In the Cerro de San. Fernando alone, included in the latter district, there were in 1840 no less than 1,700 bocaminas,-or mine openings. There are also numerous silver mines in the southern * Ann, des Mines (3), f, 11. 169. SOUTH AMERICA. 315 districts, but the amount of metal produced is small in comparison with the richness and extent of the veins. The total amount of the silver produced from the principal mines of the Cerro de Pasco from 1784 to 1827, was 4,962,929 Ibs. troy. The total annual production of the silver mines of Peru is esti- mated at 299,000 lbs. troy. Bottvi1A.—The mines of Potosi, which once formed a portion of the viceroyalty of Buenos Ayres, are now included in the Republic of Bolivia, and have, since their discovery in 1545, yielded almost fabulous amounts of silver. In this locality thirty-two principal veins, besides numerous smaller ones, have been worked in an isolated mountain called Hatun-Potocst, or Great Potosi, the summit of which reaches an elevation of 16,000 feet above the level of the sea. From the time of the discovery of these mines, up to 1571, when the process of amalgamation was introduced, the ores were treated exclusively by fusion. The Spanish conquerors of the country, being military men, were but little skilled in metallurgical operations ; and having been unable to effect the fusion of the mineral by the aid of bellows, adopted the primitive process employed by the natives for the treatment of ores obtained from the neighbouring mine of Porco, which had been in operation long previous to the conquest. For this purpose, according to Humboldt, small portable furnaces, called hwayres or guayres were established on the mountains in the neighbourhood of Potosi, wherever they could be fully ex- posed to the action of the prevailing winds. These furnaces con- sisted of cylindrical vessels of refractory clay, pierced with numerous holes, in which the silver ores were introduced, together with galena and charcoal, in separate layers. The air, which entered the holes before referred to, caused the fuel to burn with great intensity ; and when the combustion became tco active, and the consumption of charcoal consequently very rapid, the furnace was removed to some locality less exposed to the wind. Early travellers who visited the country, speak with enthusiasm of the effects pro- duced by these fires, more than six thousand in number, which, every night, lit up the mountains in the neighbourhood of the mines. The galena necessary for the operation of smelting was obtained from a neighbouring mountain called Huayna-Potocst. The argentiferous products obtained from the portable furnaces were re-melted in a fire kept up by means of copper blow-pipes, from Paik Fe SILVER. six to seven feet in length, and of which from ten to twelve, used by as many different persons, were employed at the same time. It will be readily conceived that the loss of silver experienced by this primitive process must have been exceedingly great. The period of the greatest productiveness of the Potosi mines was the century which immediately followed their discovery, their average annual yield from 1545 to 1556 having been about $11,600,000. Shortly after the commencement of the seventeenth century their production began to decline, and at its close their annual yield had receded to between three and four millions of dollars. The annual yield of the Potosi mines was estimated by Chevalier, in 1845, at from 48,000 to 60,000 Ibs. troy. Although the produce of the ore has considerably decreased, in proportion as greater depths have been attained, the mines of Potosi are far from being exhausted, and there can be no doubt but that, if intelligently worked on a large scale, under the protection of a reliable Government, they might be, at least to a great extent, brought back to their former state of prosperity and productiveness. According to Whitney there were in 1852, in the pro- vince of Potosi, abeve 1,800 abandoned silver mines, and only 26 at work ; and in the remaining mining districts of the country there were no less than 2,365 abandoned mines, and only 40 in course of working. The total amount of silver produced by the mines of Peru and Bolivia, from the earliest period up to 1845, was estimated by Chevalier at 155;839,180 lbs. troy. — Cuiti.—Domeyko, who has described the mining districts of Chili, divides the rock formations of that country into three distinct groups, viz* 1st. Secondary stratified, prior to the upheaval of the Andes. 2nd. Igneous eruptive masses, of the period of the upheaval of that chain. 3rd. Tertiary beds, posterior to that epoch; generally speaking, the veins affording gold and copper belong to the second group, whilst those of argentiferous copper, containing these metals in combination with sulphur, arsenic, and antimony, are usually included in the first. The gold veins are principally enclosed in granite, and those of copper, uncombined with silver, arsenic, or antimony, are chiefly found in diorites, porphyries, and eurites, or in some ether eruptive igneous rock. Chloride of ‘silver and the native amalgams are, in most * Ann. des Mines (4), t. ix. 22. SOUTH AMERICA. od instances, met with near the point of junction of rocks belonging to the first and second classes. The mining districts of Chili may be divided as follows :— Mountains north of the valley of Huasco—This is the richest silver district of Chili, but also contains valuable mines of copper and gold. The most productive copper mines of this section are those of Carrisal. Districts lying between Huasco and Coquimbo—In this region are the rich groups of copper veins of San Juan and La Higuera, which annually supply large quantities of copper ores of a high percentage produce. The’mines from which these are obtained, are situated in dioritic rocks. On a line between Arqueros and Agua Amarga, which represents the course of junction of the first and second groups, there are numerous veins affording metallic silver, chloride of silver, and native amalgam. The third district lies between the valleys of Coquimbo and Aconcagua, where the granite extends far inland, and the gold-bearing veins present a greater development. The whole of the granitic district is more or less auriferous, and on its borders are numerous veins affording copper ores. The fourth district lies to the north of Aconcagua, where, as in the foregoing, the granite is traversed by auriferous veins ; and mines of silver and argentiferous copper ores are worked above the level of the various ravines existing in the stratified rocks forming the elevated chain of the Andes. The usual gangues of the copper veins are quartz and hornblende ; whilst carbonate of lime and sulphate of baryta accompany the ores of silver. Gold is commonly associated with quartz and sulphide of iron. The most abundant ore of silver is the chloride, together with bromide of silver and the native metal. The chlorides are found in the usual ferruginous earthy deposits, called pacos and colorados by the miners of South America. In addition to these, there is a great variety of sulphides and arsenides of silver. The ores usually contain from 100 to 250 oz. of silver per ton; but it is a remarkable fact that the blendes and galenas occurring in the rich silver regions of Chili, as a rule, scarcely contain a trace of that metal. The most important silver mines of Chili are those situated in the neighbourhood of Copiapo. All that portion of the country lying above the parallel of Valparaiso is rocky and sterile, excepting three tongues, or narrow bands, varying from three-fourths of a mile to one mile in width, extending inwards from Coquimbo, Huasco, and 318 SILVER, * Caldera. All the remainder is a desert, and in it, at distances of from thirty to forty leagues from each other, are the various mining districts. The mines of Coquimbo and Huasco chiefly afford copper, whilst those of Copiapo are rich in silver. The principal workings are those in the vicinity of Chanarcillo and Tres Puntas; the first, sixteen leagues south, and the second, thirty to the north-north-east of Copiapo. The mines of the former locality were discovered, in 1832, by a muleteer, and were worked with large but gradually diminishing returns until 1836, when the veins were found to have been cut off by a stratum of tough lmestone, called in that country a mesa, or table. On this discovery being made, the mine proprietors of the district became generally discouraged ; but one of their number, more enterprising than the others, having sunk to a depth of 266 feet through the unproductive rock, found on the other side a rich deposit of silver ore. Several of these barren strata have since been intersected by sinking, and it has been invariably found that the veins are rich between them, and that the largest accumulations of ore are met with near the planes of contact of the limestone with the adjoining rocks. The first mine discovered in this district was that known as the Descubridora. The three principal mines of the Tres Puntas are La Buena Esperanza, La Salvadora, and the Al Fin Hallada; whilst in the district are some twenty other more or less productive and profitable workings, together with a great number producing little or nothing. The development of the mineral resources of Chili has been more recent than that of the other South American States; but its com- paratively flourishing political situation, and the internal quiet which it so long enjoyed, have enabled the workings to be established on an extensive scale, and has, within the last few years, led to a con- siderable increase in the amount of silver annually produced. Under the Spanish dominion, the production of silver was inconsiderable, and in 1800 the annual yield was estimated by Humboldt at only 18,300 lbs. troy. Since the discovery of the rich mines of Copiapo, however, in 1832, the production of silver has very much increased, The total yield of silver, up to 1810, was estimated by Chevalier at 804,000 lbs. troy, and from 1804 to 1845 at 1,803,636 lbs. The silver exported for the eight years from 1834 to 1841, both inclusive, was, according to the returns of the British consuls, based on the confessedly defective information furnished by the Chilian Government, as follows :— SOUTH AMERICA. 319 Marks. Marks. 1 Ao SE i Ne ie Ls 865 2 2a) Brought forward = 915,417 Gott fd be il ae Ae 231,988 Gods eee ees, 148,089 PROG Pee A ee Ps 163,158 Le4a Sages. 141,621 Boat tl ss ce ats 219,482 tee 2 ee ee 140,123 fee Sb B54 | ~~ £ Total . . 1,345,250 Carried forward. 915,417 Mr. Danson estimates the total exports of silver from 1804 to 1848 at $38,555,205.* Whitney considers that the production of the country from 1846 to 1853 was probably about 1,750,000 Ibs.; making the entire yield of the mines of Chili, up to that time, 4,357,656 Ibs. troy. We are without any authentic returns of the produce of the Chilian mines since that period. New Granapva.—The Santa Ana Mines are situated in the Province of Mari- quita, State of New Granada. They contain deposits of various argentiferous ores, chiefly consisting of silver-bearing pyrites mixed with native silver, ruby silver, and various sulphides. This locality also affords argentiferous galenas and blendes. The ores are enriched by a process of stamping and dressing previous to being submitted to barrel amalgamation. The mines have been worked to a depth of 120 fathoms, and the quantity of ore raised in 1864 amounted to 1,570 tons ; which, after being reduced by concentration to 453 tons, yielded 78,281 ounces of silver. The cost of grinding and amalgamation, in 1861, amounted to $43°63 per ton; the loss of mercury being 5°72 lbs. per ton of concentrated ore treated. The loss of silver was stated in that year to have been only 5°33 per cent. The following is a statement of the silver produced from the Santa Ana Mines, from 1852 to 1864, both inclusive :— Year. OZ. Year. OZ. hy Sie ee 57,169 Brought forward. 675,940 BN ee es 31,403 1BOO” soa. Bal Tyr SO eS Pepa 55,009 Le ee estan Tue on CREE pete! fo?) 84,415 WG) 0s cee 81,044 Pete st. p % ROBO 1362154. -\) bar Ron 93,436 Pied ck) gs) 108,019 1860234 bene poe LE 24 Teer... .. . 160,036 (e640 eee Fae Tere) Carried forward. 675,940 1,266,455 The following table gives the approximate yields, in pounds troy, of the principal silver-producing countries of the world, at the commence- ment of the present century, and for the years 1850 and 1865. In cases where the return for the year indicated could not be obtained, the pro- duce for the nearest year for which they could be procured has been substituted. The quoted produce ‘of the various European countries, * Quarterly Journal of the Statistical Society of London, March 1851, p. 40. + It is difficult to understand how the loss of silver should be so small with so large an expenditure of mercury. 320 SILVER. and of the United States of America, may be taken in each instance as a sufficiently close approximation ; but the figures relating to Mexico, Central America, and South America, must be regarded as estimates only. A large proportion of the precious metals produced in those countries is annually exported without passing through the hands of the Government officers, and consequently the most reliable informa- tion that can be procured is but little to be depended on. No sys- tematic investigations have been made on the spot by competent persons since the date of the writings of Duport and Chevalier. TABLE SHOWING APPROXIMATE YIELD OF THE PRINCIPAL SILVER-PRODUCING COUNTRIES. 1800. | 1850. 1865. | Ratio | Ratio | Ratio | lbs. troy. | per Ibs. troy. | per | _ Ibs. troy. per cent. | Gent. || cent. Russian Empire. . | 58,150 | 2'5 60,000 | 21 58,000 | 1°5 Scandinavia . ) | | |< '20,400-}haG7 15,000 | 0°4 | Great Britain . . | | | 48,500 | 1-7 | 60,600} 46 | Hartz eee | 31,500] 11 | 28,000 | 06 Prussia. ory ee 21,200 | 0°7 | 68,000 | 1°7 Saxony . ane lel 63,600 | 2°2 80,000 | 2°0 Other German States | sc ncateac l hayeotad 2,500 | Ol. 2,500 | Austria. . 9." . | 87,000 | 31, 92,000 | 29 France . : | 5,000 | 02 |. 1800015 Oa5 Italy sa | ae .. | *25,000 | 0-6 | Speintes ee ee ae | 125,000 | 4:4 | 110,000 | 98 | Australia, New Zea- | _ | | je aid, Balti Cos |. |, 10000 | 04 | lumbia, and Nova | | | | | Scotia ‘ | Chili. . 9. . . . | 18,300] 0°8 | 238,500 | 8-44) 299;00Gtia7aSa Bolivia tes. ¢6Segne 271,300 | 11:6 | 130,000 | 4:6 | 136,000 | 3:3 | Pera ai gta c iets 401,850 | 17-2 | 303,150 | 10°7 | 299,000 | 7:4 | New Granada... | 5,000.1, -,0:2 13,000 | 0°5 15,000 | 0°4 Ea Eee ieee oo eee BOE 1 ek O75 Pret 1,500 | 0°4 Mexico. . . . . | 1,440,500 | 61-7 | 1,650,000 | 58°4 | 1,700,000 | 42°3 United States . . a a 17,400 | 0:7 | 1,000,000 | 25-0 Total . . . . . | 2,337,300 | 100 | 2,827,425 | 100 | 4,017,000 | 100 * Obtained from the island of Sardinia, where it is found associated with galena. CHAPTER XVI. TREATMENT OF SILVER ORES BY AMALGAMATION—PATIO PROCESS, ée. PATIO PROCESS—MAGISTRAL—SALT—MERCURY—LIME—COPPER PRECIPITATE — ; COMPOSITION OF ORES—ROUGH STAMPING—FINE GRINDING—RASPAR—LOSS OF GOLD— THE PATIO— INCORPORAR— TREADING OF TORTA—WASHING — STRAINING AMALGAM —DISTILLATION—LOSS OF SILVER—LOSS OF MERCURY— CHEMICAL REACTIONS OF THE PATIO—RESULTS OF THE PATIO PROCESS — AT GUANAXUATO — FRESNILLO — REAL DEL MONTE—VIRGINIA CITY — AMALGA- MATION BY HOT PROCESS—ESTUFA AMALGAMATION. It has been found after numerous trials that the ores of silver, with the exception of argentiferous galenas, do not generally admit of mechanical concentration, and they are consequently, after careful selection, in most cases, subjected to metallurgical treatment. The difficulty of treating ores of silver by mechanical means, arises from the fact of the greater portion of this metal being finely dis- seminated in the veinstone in the form of various brittle sulphides, which, on the pulverisation of the ores, become so finely divided as to float off in suspension in the water employed for concentration. Various carefully conducted experiments made on this subject by Berthier, on samples of silver ores obtained from the different districts of Mexico, go to show that under favourable circumstances, nearly one-half the amount of silver originally present, is lost by even the most careful process of washing that can be applied to them. It must also be borne in mind that, even had the results obtained by mechanical preparation been more favourable than they have been generally found to be, the supply of water in the districts affording a great proportion of the ores of this description, is exceedingly limited, and that the inconvenience and expense attending the dilution of the argentiferous mineral by a large quantity of silicious and earthy matter, 1s less than the cost and trouble that would be entailed by their concentration. Patio Process.—The method of extracting silver from its ores, so long employed in the mines of South America, and known as the patio process, was discovered in 1557 by Bartolomé Medina, a native ¥ 322 SILVER. of the town of Pachuca, in the neighbourhood of Real del Monte. It is difficult to understand by what course of reasoning a man totally unacquainted with chemical science could have been led to the dis- covery of a process, of which the modus operands is, even now, to a certain extent, a disputed question, and of which the efficiency does not admit of being at once tested by means of a simple experiment ; but which, on the contrary, requires weeks, and, under certain circum- stances, even months, for its completion. Although, however, this process requires a considerable period for the full development of its results, the operation of reduction commences almost immediately, and we can therefore only suppose that Medina, being aware of the affinity of mercury for silver, and having mixed this substance with silver ore, sulphate of copper, and common salt, found that a certain portion of the silver had entered into combination with mercury. By keeping this mixture for some time, and occasionally testing the amount of silver taken up by the mercury, which could be readily ascertained by taking a weighed portion of the amalgam and driving off the quicksilver by heat, it would be found, that, for a certain period, the proportion of silver gradually increased, but sub- sequently remained without change. It is therefore probable that some simple series of experiments of this kind may have conducted him to the discovery of a process which has been of such vast im- portance, not only to Mexico, but to the world at large, and has so materially affected the total production of silver. A Peruvian, of the name of Carlos Corso de Leca, discovered, in 1586, the method of reduction by iron, el beneficio de huerro, which consists in adding to the torta small pieces of iron, by which the reduction of chloride of silver is effected, attended by a corresponding saving of mercury. This process does not, however, appear to have been ever extensively employed. ; The next modification in the process of amalgamation was intro- duced in 1590 by Alonzo Barba, which consisted in conducting the operation in large copper vessels heated by means of a fire placed peneath them. ‘This process, called e beneficio de cazo y cocumento, effected a considerable saving of mercury, attended by a correspond- ing loss of copper, since the chloride of silver is reduced at the expense of the vessel in which the amalgamation is carried on. This process, by which the reduction of the chlorides is readily effected, | but which is not equally applicable to sulphides, was introduced into Europe in 1784 by Baron de Born, an Austrian mining officer, by AMALGAMATION— PATIO PROCESS. 393 whom its use in the Hungarian mines was recommended, and from which ultimately sprung, in 1790, the barrel process of Freiberg. It would, however, appear from.a work on Metallurgy by Schliiter, printed in 1738, that a process of amalgamation in barrels, or rather vertical tubs, was in use at Kongsberg, previous to that period. Not having had an extensive practical experience in the extraction of silver from its ores by this method, we have availed ourselves of the descriptions given of it by Humboldt, Duport, and other compe- tent authorities, as well as of data contained in various foreign’ journals, and in a paper by Mr. J. Napier, jun.* We have also had access to notes made by various friends long engaged in different large reduction establishments in Mexico, and who have furnished valuable statistics relative to the cost of the different operations. The materials necessary for the reduction of the ores of silver by the patio process, are magistral, common salt, and mercury; but in addition to these, sulphate of copper, precipitated copper, and copper and zinc amalgams are occasionally employed. Magistral—tThis is manufactured from copper pyrites, or raw magis- tral, of which mines occur in many parts of Mexico, but particularly in the district of Tepezala, about twenty leagues south-east of Zacatecas, and sixty from Guanaxuato, from which a large supply is obtained. — The following estimations of copper, made by Napier, show the average percentage of that metal contained in ores from this district :— Copper per cent. No. 1=13°00 ] ea ar be Lets ED iS gs: 5 4= 9°00 »» 5=12°50 r = 10°32 mean percentage of copper. 5 61050 a) ft OU ys ee 40 » 9= 873 J The copper ore, when brought to the works, is first reduced to a coarse sand by dry stamping, and then ground to a fine powder in arrastres. The ground ore is removed from the arrastre to an enclo- sure, where the water, with which it has been mixed during the process of grinding, is allowed to evaporate ; it 1s then left exposed for a long * “On the Mexican Method of Amalgamation,” by James Napier, Jun., late Chemist and Assayer to the Guanaxuato Mint, Mexico. Mining and Smelting Magazine, vol. i. p. 101. + ae d24 SILVER. time to atmospheric influences, as it is generally believed to afford a, larger proportion of sulphate of copper by roasting, if previously exposed for some months to the action of the air. The furnaces in which the calcination is effected are called comalillos, and have a double hearth, of which the roof is almost flat, with a fireplace at the side. About eight arrobas, or two hundred pounds, of ground ore, with which a few handfuls of salt have been previously mixed, are charged on each hearth. The heat is then gradually raised, and the ore kept constantly stirred during from six to eight hours, when the doors are closed, and the furnace allowed to cool. When sufficiently cold, the doors are again opened, and the charge raked through holes in the bottom of the furnace into arched recesses beneath, prepared for its reception. The percentage of sulphate of copper formed, from an ore of given tenure in copper, depends, to a great extent, on the skill of the workman, and the care bestowed on the operation. The following table gives the results obtained from the roasting of different parcels of copper ores at the various reduction works at Guanaxuato, as determined by Napier :— Sulphates per cent. Total agen state pipes: Name of Hacienda. ; paneer ees PERCE RE Ges oc sc in One Copper. “4° Iron. Sulphates. | As Sulphide.| As Oxide. ee g. San Joaquin . 40°99 9°73 50°72 4:50 yA 6 15°30 » Nicolas . 20°50 | 12°38 | 32°88 2°50 0:23 7°83 Granaditas . . 34°37 6°95 41°32 3°78 2°47 14:00 Salgado. . . | 24°64 | 740 | 32°04 ae 2°50 8-00 Pagde SV) FL AR BP Syl. BTSs e093 3°00 3°50 12°80 Pastita i so: 31°62 9°05 40°67 | 0°70 O15 8°75 In the above table the amount of sulphate of iron is given, as well as the proportion of sulphate of copper, since it has been found that sulphate of iron, as well as the former salt, may be considered an agent in the reduction of the ore, although its action is neither so rapid nor so complete. A small portion of the copper estimated as sulphate will also be in the state of chloride, produced by the chemical changes resulting from the decomposition of the common salt added to the charge. When the ores treated contain either oxide or car- bonate of copper, it is usual to add to them a certain amount of iron AMALGAMATION—PATIO PROCESS. 325 pyrites, which, by supplying sulphur, assists in their conversion into sulphates. The sulphate thus obtained, being in an anhydrous state, becomes heated on the absorption of water, and this circumstance is taken advantage of for the purpose of making a rough estimate of the quality of prepared magistral, and determining the proportion it will be necessary to employ. For this purpose the amalgamator takes a small quantity of the calcined ore in his hand, and then gradually inserts it into water, judging from the degree of heat developed, of the quantity of sulphates contained in the parcel. It is also considered by some amalgamators advantageous to employ the magistral as soon after its calcination as possible, since by absorbing moisture its action is said to become less energetic, and a larger amount to be required. The quantity of water, however, which could be absorbed from the atmosphere by the magistral, is so small, in comparison with that contained in the argentiferous mud with which it is incorporated, that the moment they become mixed the whole of the anhydrous sulphate present must at once become fully hydrated; and it is therefore difficult to ascribe the belief that it is necessary to employ freshly calcined magistral, to any- thing but prejudice on the part of those who entertain the opinion. That such is in reality the case, appears to be evident from the fact that the whole of the sulphate of copper derived from the opera- tion of parting at the various mints, is purchased for the purpose of being employed in lieu of magistral, and that preference is now given to this hydrated salt by the more intelligent amalgamators. Salt—In addition to the salt imported from the sea-coast, a very large proportion of that employed in the mining districts of Mexico is obtained from various lagunes situated at more or less con- siderable distance from the mines. Large quantities of impure salt derived from this source, and forming an efflorescence on the surface of the ground during the dry season, were formerly employed under the name of saltierra for the purpose of amalgamation. The cost of transporting large quantities of such an impure material, added to the great increase, in bulk, of the tortas, caused by adding the amount necessary to furnish the required quantity of chloride of sodium, has, however, caused its use to be nearly abandoned; the salt is therefore now generally concentrated by lixiviation and evaporation before being brought to the mines. | The principal localities from which saltierra was formerly derived, and where salt is now manufactured for mining purposes, are Salinas, 326 SILVER. and Pefton-blanco, there being in both localities, in addition to the saline incrustations before referred to, springs holding chloride of sodium in solution. The following analysis, made by Berthier, of the saltierra from Penon-blanco, gives the composition of the material formerly employed instead of salt, and shows how large a proportion of its constituents must have been totally inert when introduced into the torta:— Chloride of Sodium . . . +. 19°00 Ade See Sulphate of Soda . - . = . 290; Fe eee Carbonate of Lime . . . . 18°60 a4 Magnesia . . . 1°60 Oxide of Iron . . . . . . 9°80 } insoluble in water. ClayandSand. . . . . . 46°20 Water and Organic Matter. . 7°60 J 100°00 The amount of chloride of sodium contained in the purified salt from Pefon-blanco is usually from 80 to 85 per cent. ; the remainder, for the most part, consisting of sulphate of soda. The following table gives the composition of four samples of salt supplied by the district of Salinas, analysed by Napier :-— : No. 1. No. 2. No, 3. No. 4. Chloride of Sodium . . . « 96°623 91°141 90°422 86°853 * Magnesium . . . 6008 2'538 2°520 0°044 fs Catenin. |S se 1574 1310 0125 Sulphate of Potash . . - - Trace 3141 3°556 0029 x Sodat cn ka a ee eee oe on 12°949 bib 6 245 5 Gains te 1°606 9°192 99 100:000 1007000 100°000 =100°000 The purest-description of salt employed in Mexico is that brought from the sea-coast, which often contains as much as 95°50 per cent. of chloride of sodium, but its great cost prevents its general employ- ment in the reduction works of the country. , Mercury—Nearly the whole of this metal, of which the consump- tion in the Mexican mines is very large, is imported from Europe and California, although it has been found in various localities in the empire, particularly at Mazapil and the Gigante, near Guanaxuato. These mines are not, however, now worked, although considerable quantities of quicksilver have, at various times, been obtained from them. The district of El Doctor, 150 miles north of the city of Mexico, has also furnished a certain amount of this metal. . AMALGAMATION—PATIO PRCCESS. eT Lime.—This substance cannot be regarded as an essential in the patio process of amalgamation, since it 1s only employed when too large a proportion of magistral has been added to the torta, and is then used for the purpose of decomposing the excess of sulphates. Wood ashes are also sometimes made use of for the same purpose. Copper Precipitate—Instead of using lime for the purpose of coun- teracting the effects of any excess of sulphate of copper which may have been added, precipitated copper is employed in many of the haciendas, and acts by the reduction of the metallic chlorides. The use of copper precipitate in the process of amalgamation by the patio was first introduced by Mr. Louckner, who also, in conjunction with Mr. Mackintosh, obtained a patent for the employment of copper amalgam in the torta, with a view to reducing the loss of mercury. This patent was, however, readily evaded by the use of precipitated copper, which, by combining with the mercury, produced the same effect. Composition of Ores—The ores subjected to patio amalgamation differ somewhat in their composition in the various mining districts. The following analysis gives the composition of an ore of more than average richness, from the district of La Luz, Guanaxuato :— Soya) Ip ae eS en ee 8 Penis, Me ete OO ae ee, ee rene: 5 A COUPE tee te were ty. ly es, 4 Oe Upnureews. Veta Se. Pe. LOD Arras OF liliGua) a2 5.) sev) ., @Bred - Mammen yet Coe ok eG SITES ee” "Se eer ar eermer es 6D 99°60 The ores of Real del Monte vary considerably in their composition, but often contain manganese, antimony, and lead; and are conse- quently difficult of reduction by the patio process of amalgamation. A sample of ore from the Santa Brigida vein, analysed by Mr. tozers, afforded him the following results :— REL VMDEee es, be Ge rie RS ort ty 6 oe Bie Pg me thE ae A (0°25 Peers. OL COTE: whe, iregiraih fi Sen eee Shy mlveu 0°40 Z PR Re a, ae Pic te FEBS OL ed eax 2°30 a LGPL od s et ee ee ee eae 2°82 Peroxide and. pulphide. of Iron... 05 a. 7°50 PpOS eVLSTICATION fet pos, ea BEE, sheen a. (Re he 5°30 Sarriemorwari. ow ie eae A eh & 18°57 328 SILVER. Brouvhiiforward) 3. 0 se Se AMHIGA Ri ke Ck ig by ee Lo, (eh. fe es ee 8:00 Carponato ot iamen: coc on So. ee 1°45 ‘3 Magnesia) oa rat) ecu tig yet o Masee eee 1°60 Se LN RUM asl 68°00 Antimony, Tellurium, traces of Gold, Potash, and Soda 2°38 100 00 An average sample of the ores worked in the district afforded the following result :— Sulphide of Silvers... i, a) tee ca Gee Fa ATOM Ree Sea eee en eer 2: Leary fe Ee eG be ATSONIG) fo PRAY eee . VAt Me aa MM BAe Reve ee Le e525. Sulphate-of.fronigy. 2 tice aie ee is Dime ea se ee Re Peroxide of Manganece . . . . . 3°54 Carbonateof Time 2... paacena ee i Magnesia: 2° SOG RULLCRY war He + raat. biel Phe, oe cea Moisture: 37 55 ae ne set peice 100 00 In the mining districts of Mexico, as well as in Nevada and other localities producing silver ores proper, there are immense accumu- lations of veinstone containing in the aggregate vast quantities of silver, but of which the yield is not sufficiently high to admit of their being treated with profitable results. Numerous plans have been proposed, and various machines invented, with a view to the concentration of these ores by washing, but, as before stated, none of them have hitherto been found capable of extensive practical application. Rough Stamping.—The ores to be subjected to the process of patio amalgamation are usually first crushed dry, to the state of coarse gravel in a stamping mill, and subsequently reduced by porphyrisation in the arrastre to the necessary degree of fine division. ‘The former machines generally consist, in Mexico, of eight wooden lifters or stems, shod at their lower extremities with iron, and set in motion by cams, worked by a water-wheel, or more frequently by a team of mules. The ore, as fed to these morteros or stamping mills, is in pieces of about the size of the fist; and, as it is broken, falls into sieves formed of hides perforated with small round holes, and fixed in AMALGAMATION—PATIO PROCESS. 329 an inclined position before the battery: the portion of the ore which passes through these sieves is removed to the arrastres to be further ground, whilst the coarser particles, remaining on the skins, are again thrown back into the mill. In the majority of the reduction esta- blishments of Mexico this work is entirely performed in mills worked by relays of mules which are driven at a rapid rate, and frequently replaced by a fresh team. Each molino requires eighteen mules, which are successively harnessed to the machine in sets of three. An apparatus of this description will, in the course of twenty-four hours, reduce about five tons of ore to a state suitable for treatment in the arrastre. Fine Grinding—The arrastre or tahona employed for this purpose is constructed as described, page 168: but is paved with great care and is very strongly put together. The bottoms are constructed of hard porphyritic stones about thirty inches in length, placed vertically, and the interstices carefully filled with cabecilla, which is the residue remaining after the washing up of atorta. The sides are formed of either wood or flagstones, which stand about two feet above the level of the floor. Their diameter in the haciendas of Guanaxuato is 44 varas, or 12 feet 4 inches, arrastres of this size being called arrastres de marca. The voladoras, or mullers, are of porphyry, and have a length somewhat less than the radius of the arrastre, with a thickness of about sixteen inches. In each of them are bored two holes, into which are driven wooden pegs for attaching the chains or straps of raw hide by which they are connected with the arms traversing the vertical shaft. Each arrastre is provided with four voladoras, and is worked by a team of two mules. In certain districts, as at Real del Monte, basalt is sometimes employed for mullers, but, although sufficiently hard for this purpose, it has a very close grain, and consequently, when once it has become smooth, it passes over the ore without causing the grinding effect pro- duced by porphyry, which being coarser in its texture, retains a good rubbing surface to the last. As soon as the bottom of an arrastre has been put in, a new voladora is set to work to grind cabecilla, to which a certain quantity of water has been added, and by which the interstices between the stones are gradually filled. This is continued with one muller during the first day, and on the second another is added, with which the operation is carried on until the end of the third day, when another grinding stone is attached, and the treatment of poor ores may be commenced, After the expiration of four or five days, the 330 SILVER. fourth stone is put on, and the surface of the grinders and of the bottom of the arrastres, having now attained their normal condition, ores of the usual degree of richness may be charged into the arrastre, and fine grinding carried on in the usual way. Extraction of Gold.—In districts such as Guanaxuato, where the ores contain, in addition to silver, minute quantities of gold, the latter metal could often not be advantageously separated from the former if obtained together in the form of an alloy; but by keeping the arrastre constantly charged with a certain quantity of mercury, or with an amalgam of silver or copper, the gold is so concentrated in the result- ing amalgam, as to afford highly profitable results. This method of effecting the concentration and extraction of gold appears to have been long employed in some of the mining districts of Mexico, but Humboldt states, that at the time of his visit to Guanaxuato in 1804, it had not been introduced into that neighbourhood. At Guanaxuato, where the ore is more finely ground than in any other district in North America, an arrastre is charged with from six to eleven quintals of granza or coarse sand from the stamping mill, to which are added about ten gallons of water, which is sufficient to bring it to the state of a thick mud; and on the amount of water thus added, will very much depend the degree of fineness to which the ores can be reduced. If the arrastre be a new one, or one from which the amalgam has previously been removed, from five to ten pounds of silver amalgam are introduced. For this purpose some amalgamators prefer a very dry amalgam, whilst others employ a larger proportion of mercury ; but it appears to be generally admitted that a tolerably dry amalgam is to be preferred, since, if it contained a large quantity of mercury it would be lable to run into the crevices of the bottom, and thus cease to be of any advantage to the operation. _ When, on the contrary, the amalgam made use of is moderately dry, it not only spreads itself over the surface of the bottom, under the influence of the grinding action of the voladoras, but is also believed to possess a stronger affinity for gold, and to form with it an amalgam more readily than pure mercury would under similar circumstances. The arrastres used in the haciendas of Guanaxuato are in most cases charged each morning at four o’clock, when, as before stated, a barrel of water, containing about ten gallons, is introduced at the same time with the ore; at nine o'clock another barrel, or sometimes a barrel and half is poured in, and at twelve o'clock one barrel, at three o’clock three barrels, and at four, five barrels are added. The AMALGAMATION—PATIO PROCESS. Sa quantity of water used, will however somewhat depend on the nature of the ores operated on. As the operation of grinding progresses, the amalgam by degrees accumulates in the crevices in the bottom of the arrastre, and every alternate morning a small sample or ¢entadwra 1s taken from the amaleam in the bottom of each arrastre, cleaned well by washing, and its condition carefully examined. Its dryness or moistness is judged of in accordance with its behaviour when pressed by the thumb against the side of the jicara containing it, and from the result thus obtained is estimated the amount of mercury, if any, that is required to be added to the arrastre previous to the next grinding. The usual amount of mercury added is about half a pound every second morning, although this will ina great measure depend on the richness of the ores that are being worked, but as a general rule the amalgam should not contain above twenty per cent. of gold and silver. The amalgam is usually removed from the arrastres every three months, but in some instances they are cleaned up at even longer intervals. At the expiration of twenty-four hours, when the grinding is completed, the Jama, or slime, is baled out into a barrel, in which it is removed to reservoirs, formed in masonry, from which a portion of the water becomes evaporated by exposure to the sun and air, and leaves the mass in a fit condition for subsequent treat- ment in the patio. In some establishments, instead of the lama being transported in barrels to these reservoirs, it is baled into launders by means of which it is conducted to the proper receptacles ; whilst in others it is tapped from a plug hole at the bottom of each arrastre directly into these launders. When the lama is dipped out in a batea, a plate of iron, or some other metal, is laid on the bottom of the arrastre for the purpose of preventing any of the rich amalgam from being scraped up by the batea and becoming mixed with the slimes; after this operation, which occupies at most about half an hour, is completed, the arrastre is charged with a fresh quantity of eranza and the process of grinding is again proceeded with, as before described. ‘The mules, by which the machine is worked, are changed every six hours, the arrastres being generally arranged in a double row on either side of a long shed or galera. The augmentation of weight which takes place during the opera- tion of grinding, and due to the wearing away of the voladoras and bottom of the arrastre, usually amounts to from eight to ten per cent. The bottom will often continue in good repair during twelve months, but the grinding stones or mullers seldom - last Sou SILVER. beyond a month, and are sometimes worn out considerably within that time. Raspar.—The removal of the amaleam from the arrastres is called the vaspando or scraping, and takes place more or less often in accordance with the quality of the ores under treatment. The arrastres are, however, seldom cleared of amaleam more often than once in three months, and in some instances only once in six months. This is done by removing, with a hooked iron scraper, all the sub- stances which have accumulated between the stones forming the bottom of the arrangement, and which consist of a mixture of coarse fragments of gravel, finely ground ore, and an amalgam of silver and gold. If the bottom of the arrastre has been entirely worn out it is removed, and every stone well scraped and cleaned, after which a new bottom is put in as before described. The substance collected either by scraping out the interstices between the paving of the arrastre, or by cleaning every portion of stone forming part of the old bottom, is next carefully washed in bateas in a tank filled with water. or this purpose, a portion of the stuff to be washed is placed in the wooden bowl, and a little fresh mercury added to it, for the purpose of collecting the finer particles of amalgam, and preventing them, as much as possible, from being floated off on the water. In this way the principal portion of the amalgam is collected in the bowl, whilst some of the smaller particles, mixed with the lighter earthy impurities, become deposited in the bottom of the tank, from which they are subsequently removed for the pur- pose of being re-washed on an inclined table, called a planilla. The amaleam, after being collected and cleaned, is first freed from a portion of its mercury by straining through a leathern or canvas bag, and then retorted and sent to the Government Assay Office, where it is assayed and melted into bars, and then forwarded to the Mint, for the purpose of being converted into coin. Loss of Gold—The yield of gold obtained by this method of treat- ment is considerably less than the total amount contained in the ores, as indicated by assay ; the loss experienced being generally believed to vary from 25 to 40 per cent. on the assay produce. Various circum- stances contribute to produce this deficit in the gold. In the first place, there is always a loss of finely-divided amalgam during the process of washing up the various substances obtained by scraping the bottoms of the arrastres. Secondly, the silver subsequently ex- tracted by amalgamation in the patio, invariably contains a small AMALGAMATION—PATIO PROCESS. Joo proportion of gold; and thirdly, the polvillos remaining from the washings of the ¢ortas, and which principally consist of argentiferous iron pyrites, also retain a certain amount of gold. These polvillos, or relaves, are subjected to a process of roasting in a reverberatory furnace, and a second grinding in the arrastre, after which they are a second time subjected to the process of patio amalgamation. Loss of Mercury in the Arrastre-—It was formerly believed that by the process of grinding the ores of silver and gold with mercury, those portions only of the metals which exist in the metallic state are obtained in the form of amalgam; but this is evidently not the case, since there can be no doubt that more or less of the sulphide of silver is always reduced to the metallic state at the expense of a corresponding amount of mercury, which is itself converted into sulphide. It is also generally well known to azogueros, or amalga- mators, that to obtain a given weight of the precious metal by this process, a nearly equivalent quantity of mercury must be sacrificed, and this could by no means be accounted for, on the supposition of its uniting only with the free gold and native silver present in the ores. Fe The following figures are given by Napier as the result of an experiment made at one of the reduction works of Guanaxuato, and go to show that the loss of mercury is mainly due to its combination with sulphur, derived from the reduction of sulphide of silver :— The amalgam added to an arrastre weighed 70 lbs., and was composed of 14 lbs. of silver combined with 56 lbs. of mercury. The mercury added, exclusive of that in the amalgam, weighed . 330 lbs. Mercury inamalgam . . . Ses SPE Plata Mixta, gold and silver btaited: ciate ally er ded in ALERT HTT eee gy ig ee a eile ay ons Sy ASLEEE OOS oh Weight of amalgam which should have been obtained . . . . 470 Ibs. The amalgam actually produced only weighed, however, 400 lbs., and consisted of 84 lbs. of gold and silver, and 316 lbs. of mercury, showing a loss of 70 lbs. on the total quantity of quicksilver intro- duced into the arrastre. The alloy obtained, consisted of 18 lbs. of gold, and 66 lbs. of silver; and as the gold, being in the metallic state, must have united directly with the quicksilver without entailing any loss of that metal, the deficit may be regarded as equal to the weight of the silver taken up, the slight excess of loss observed, being readily accounted for by mechanical loss in washing, and the escape of mer- 334 SILVER. curial vapours during the subsequent process of retorting the amalgam. The ores of Guanaxuato contain scarcely any native silver, gold being practically the only metal present in the metallic state, and conse- quently the loss of mercury can only be ascribed to the reduction of sulphide of silver by mercury, and its gradual conversion into the sulphide of that metal.* When copper amalgam, instead of an amalgam of silver, is introduced into the arrastre, the copper gradually disappears, and is replaced by silver, the loss of mercury being at the same time less than under ordinary circumstances. When the ores to be treated do not contain a sufficient amount of gold to render its extraction a profitable operation, they are ground in the arrastre without the addition of mercury; and in some localities, as in Zaca- tecas, the grinding is not so long continued, and the ore 1s con- sequently reduced to a less finely divided state. In the locality last named, an arrastre of similar dimension to those employed at Guanaxuato, grinds ten quintals in the course of thirteen hours, but the resulting lama is much coarser, and it is probable that the less satisfactory results generally obtained in this district may, in a great measure, be attributed to that circumstance? The Patio—The patio is a large court-yard, generally paved with flagstones, of which the joints are carefully cemented in order to prevent the loss of mercury which would otherwise take place. This flooring has given to it a slight inclination, in order that any water falling on it may the more readily run off. In ‘some cases, however, as at the hacienda of Regla, near the Real del Monte, a wooden flooring is employed instead of a stone one; and the patio, comprising an area an acre and a half in extent, is carefully covered with a wooden floor, on which a thousand tons of argenttferous slimes, mixed with thirty tons of salt, three tons of sulphate of copper, and eighteen thousand pounds of mercury, are constantly spread in dif- ferent stages of the process of amalgamation. Wooden floors were also employed in the various reduction works near Virginia City, into which the patio process was introduced, but as the climate of Nevada was not favourable to this system of amalgamation, its use has, for the present, been discontinued. The following woodcut, Fig. 40, represents the patio at the Gould and Curry Works, near Virginia. The ground slimes, on their removal from the arrastres or tahonas, * The equivalent of silver being 108, and that of mercury 101, sufficiently explains why the loss of mercury should about equal the weight of silver taken up by that metal. AMALGAMATION—PATIO PROCESS. 33D are deposited, in an almost liquid state, in walled receivers, called cajetes ov lameros, where a portion of the water is removed by evapor- ation, and where it is allowed to accumulate until there is a sufficient quantity to form a heap or torta, which at Guanaxuato usually consists of sixty montones.* When the amount of lama necessary for a torta Fia. 40. Patio AT THE GouLD AND Curry, NEVADA. (From a Photograph.) has been collected in the cajete, it is carried out into an enclosure formed on the patio, about thirty feet in diameter, generally made by laying on each other square beams of wood, kept in their places by large stones, and made tight by filling the joints either with clay or horse dung. Into this the lama is introduced, until it forms a layer of about a foot in thickness, and is allowed to remain until by * The weight of the monton varies in different localities— In Guanaxuato a monton usually contains 32 quintals ,, Real del Monte, Pachuca, and Tasco . 30 és ,, Zacatecas and Sombrerete. . . . . 20 , LETT Tk SG SEY NP Roe ee TOES = os eGR ere eee FO ly ee LO : 336 SILVER. the evaporation of the water, it has gained the consistency of a rather thin mud. This condition being arrived at, the amalgamator proceeds to ensalmorar, t.e. from three to five per cent. of salt is added in accordance with its quality, and the nature of the ores under treat- ment. It is, however, well known, that the larger, up to a certain point, the proportion of salt employed, the more rapid will be the action of the torta, although many amalgamators never employ above three per cent. of this substance, notwithstanding that an additional two per cent. would have the effect of completing the operation at least six days earlier; but the time thus gained is not found to compensate for the extra expense entailed. When the salt has been added to the torta, it receives the first treading, or repaso, after which it 1s allowed to stand until the following day, when the whole of ‘the salt will be found in a state of solution, and thoroughly and regularly mixed with the lama composing the heap. Incorporar, &e.—The day after the salt has been thus mixed with the lama, the addition of magistral and mercury takes place. For this purpose the torta is, if necessary, brought to the proper consistency by the addition of water, and the magistral thrown evenly over its surface by means of wooden shovels. The proportion of this reagent to be added varies, to a certain extent, in accordance with its richness in sulphate of copper; but in the case of employing magistral of the usual strength, something less than one per cent. is generally found sufficient. As soonas the magistral has been spread over the surface of the torta, it is again trodden by mules for about an hour, when the mercury necessary for the completion of the operation is generally added, the quantity required being from 3} to 4 lbs. for every mark of silver supposed to be contained in the heap. The introduction of mercury is effected by making it run through a linen cloth in such away that its particles may be divided in the state of minute globules, and great care must be taken that the torta be not too wet, since in that case the mercury will be lable to collect in large masses. The lama should not, on the other hand, be too dry, as the mercury would then become very finely divided, and a considerable loss, both of that metal and silver, takes place in the washing up of the torta. The exact consistency to be given to the metalliferous mud, in order to obtain the best possible result, can only be determined by practice ; but it should be in such a condition that the feet of the animals treading it may pass readily through it, and yet leave behind them distinct prints of their hoofs. After the addition of the mercury AMALGAMATION.—PATIO PROCESS. 337 the torta is again trodden for about four hours, in order to effect its intimate mixture throughout the whole mass. When crystallised sulphate of copper is employed in lieu of magistral, from 7 to 9 Ibs. are added for each ton of ore contained in the torta. When the magistral and mercury have been added to the torta, and it has received the first treading, chemical action at onee com- mences, and it becomes necessary that the azoguero should closely watch its operation, by taking frequent samples or tentaduras ; the colour and general appearance of the mercury being the chief guides by which he is enabled to judge of the progress of the operation. Shortly after the incorporo, the azoguero takes a sample collected from thirty to forty different places, in the torta, and washes it carefully either in a jicara or in a horn spoon, similar to that sometimes em- ployed for testing samples of gold quartz in California, and, after removing the earthy particles, carefully examines what remains, which consists of polvillos, or metallic sulphides and mercury. The latter at this stage of the operation contains but little silver, and its colour and state of division afford the only indications of the more or less satis- factory working of the torta. If the mercury be found divided into minute globules, or if its natural colour has been but little changed, except that it has acquired a slightly yellow tinge, it is considered a proof that a sufficient amount of magistral has not been added. When, on the contrary, the mercury is of a deep grey, or leaden hue, it is evident that there has been too large a proportion of magistral introduced into the torta, which is said to be hot, and it may be found necessary to add a little lime in order to prevent an undue loss of mercury. When the heap is in good working order, the sur- face of the mercury presents a distinct light grey appearance, and although it is of course desirable to at once introduce such a pro- portion of magistral as will immediately throw the torta into good working condition, it is better that the amount of this ingredient should be too small, than that it should have been added in excess. When the magistral has been added in proper quantity the appear- ance of the tentadura will, on the day after the repaso, be found to have considerably changed. The mercury, if now pressed with the thumb against the side of the jicara, or bowl, is found to contain silver amalgam, and what, at the first trial, appeared as desecho, or broken-up mercury, has now become limadura de plata of a whitish colour and in the form of thin scales, which, when rubbed, are found to consist of dry silver amalgam, or pasilla. When this makes its Z 338 SILVER. appearance shortly after the addition of magistral and mercury to the torta, it is a proof that the former has been added in proper pro- portion, and that the operation is progressing favourably. To make a tentadura, a fair sample of about eight ounces, taken from different parts of the torta, is placed in a jicara, and slowly washed so as to remove the lighter portions only, leaving in the bottom the limadura de plata, the mercury with its /sta or tail, and» a portion of the heavy sulphide of iron. A little water is now taken in the jicara, and a peculiar motion given to it so as to arrange its contents in the following order: the limadura occupies the upper portion of the bowl, next come the sulphides contained in the ores, and last of all the mercury and amalgam, in the form of a large globule. As the most important indications are to be obtained from the condition of the limadura, this is first examined by holding the bowl in an inclined position in the right hand, whilst with the thumb of the left hand it is rubbed against the side of the vessel. Whilst this is being done, its colour is carefully observed, as well as the facility with which it can be converted into amalgam, and the con- sistency of the amalgam so produced. The metalliferous portions of the ore are generally passed over as not affording any information relative to the progress of amalgamation, but the globule of mercury at the bottom is examined with regard to its colour and the amount of amalgam it contains. The latter is determined by pressing it with the thumb against the side of the bowl. Three tentaduras are usually made on each torta daily ; one in the morning before commencing to tread, another after it has been trodden for some time, and a third after the repaso has been completed. In selecting samples for the purpose of making a tentadura, it is necessary to take portions, not only from the surface of the heaps, but also from the interior, since the top from being exposed to the action of the sun and air is always in a more advanced condition than the middle of the heap. The treading of a torta has the effect of stimulating the action of the magistral, and is repeated, every alternate day, as often as the tentaduras indicate a necessity for doing so. Formerly, the mercury was not all introduced at once, and after from fifteen to thirty days, according to the season, &c., it was found to be no longer in a liquid state, but had been wholly transformed into a dry amalgam from which quicksilver could no longer be obtained by pressure between the finger and thumb. SY / y \ \ 8 ~ y Pal ye es a \ wo ye yo Ge AWG Ny Os . = y- Y Dae y. eS mS Wan rary, Ji [exes | : = ge YArNI-A \ Ne nag at 4 Yj) —— \ x 4 7 = —-, . ae ey ae Pe \ 4 > Z CZ Y \ \ —- ZT WELLL IIL TELL Lilla Zz UY, MM ae Y V) MN] wg au Tetra my pity 7 CAPELLINA. (From Tilmann.) which the amalgam is supported beneath the bell B, on a stand 4, enclosed in a cast iron vessel c, kept cool by means of a current of water constantly flowing beneath the bottom, and through the annular cavity D. The condensed mercury escapes, as soon as deposited, by means of a wrought iron pipe, into a proper receiving vessel. In some cases, the charcoal is retained in its place by means of a circular iron grating. The interior measurements of the bell are usually as follow: height, 3 feet; diameter, 18 inches; thickness of metal, 14 inches. The charge of amalgam is about 2,000 lbs., affording 400 lbs. of silver; the consumption of charcoal per charge is 500 Ibs. Loss of Silver —The loss of silver by this process of amalgamation is considerable, but varies in different localities, in accordance with the nature of the ores operated on, and the degree of fineness to which they are reduced by grinding. At Guanaxuato, the average loss may be estimated, on docile ores, at from 10 to 14 per cent. At Fresnillo, the results of assays made during a year on ores containing a con- siderable quantity of galena, pyrites, and blende, as compared with 300 SILVER. those actually obtained from the patio, showed a deficit equal to 28 per cent. of the assay produce. According to Duport, the loss experienced on the ores from the Veta Grande, at Zacatecas, which contain a large amount of antimonial sulphides of silver, averaged from 35 to 40 per cent. of the produce, as indicated by assay. A portion of this loss is, however, mechanical, occasioned by particles of amalgam being carried off by the water employed for washing the lamas, after amalgamation; and a more efficient system of separation would, consequently, have had the effect of reducing the amount of silver so carried away. In some establishments, and particularly at Guadalupe-y-Calvo, the sulphides resulting from the ordinary process of washing in the lavadero are subsequently treated on shaking tables, and the results obtained are stated to be satisfactory. Loss of Mereury.—It has been long established as a principle among Mexican azogueros, that, in order to obtain a given amount of silver by the process of patio amalgamation, it is absolutely necessary to sacrifice an equal weight of mercury. To this deficit of quicksilver they apply the name of conswmido ; whilst any excess of loss above this amount, and which is considered to be due to want of care, and mechanical causes, is called perdida. The total loss of this metal may be consequently divided into two elements, of which one is constant and the other variable, and to which different names are applied. All calculations are made, in Mexico, with reference to the produc- tion of a mark of silver weighing eight Spanish ounces (3,550°5 gr.); so that, in case of the total deficit of mercury being twelve ounces per mark of silver, an azoguero would divide the loss as follows :— Consumido . . . . . 8ounces 3,550°50 gr. Perditig. ooo cs Pee ee 1,775°25 ,, - It is, however, evident that this principle is not of universal appli- cation; since metallic silver, which occurs in considerable quantities in certain ores, combines directly with quicksilver, forming an amal- gam of which the weight corresponds with the united amounts of the two metals weighed separately. The total loss of mercury varies in accordance with the nature of the ores, the method employed for washing the contents of the torta, and the greater or less proportion of native silver present. In many cases this loss does not exceed ten ounces per mark of silver, whilst in others as much as twenty-four ounces of quicksilver are expended for each mark of silver obtained. The average loss may probably be taken to vary from ten to sixteen AMALGAMATION.—PATIO PROCESS. 301 ounces per mark of silver extracted. The time necessary for working a torta varies, according to circumstances, from fifteen to forty-five days. Fine Stamping—At Real del Monte, where the Freiberg process of amalgamation in barrels is extensively employed, the ores are for this purpose reduced by wet stamping. The arrastre, although the slimy nature of the ore ground by it.is well suited for patio amalgamation, yields a bad return for the mechanical power employed, and the slimes produced are not well adapted for the barrel process, for which fine sands are found preferable. The great augmentation of weight and bulk arising from the gradual wearing of the grinding- stones is also an objection to this apparatus, and it has consequently been found advantageous to grind the ores destined to be treated by the Freiberg process in ordinary stamping mills. Into these the ore is gradually fed by a hopper, a small stream of water being at the same time introduced, which, displaced by the successive falls of the heads, carries with it all the finer particles of ground ore which float over an inclined plane, whose height regulates the fineness of the grinding. The ground ore is subsequently conducted into large tanks, in which it becomes deposited ; the water finally passing to a pump, by which it is elevated and returned to the stamps coffer, to again commence its duty as a sorter and carrier of the reduced ore. Thirty stampers, when driven with a velocity of from sixty to eighty blows per minute, grind weekly 100 tons of hard quartz to an exceedingly fine sand. The consumption of stamp heads, where such mills are em- ployed, is necessarily very great, and to effect the annual reduction of 35,000 tons of ore at Real del Monte, not less than 60 tons of cast iron are expended; but as new heads can be obtained at iron works in the immediate vicinity of the mines, they are readily replaced at a moderate cost. In some localities in which water power is abundant, the ores are sufficiently reduced by the stamping mill to fit them for treatment in the torta without a preliminary grinding in arrastres. Roasting —The minerals destined for being worked by patio amal- gamation are, in Mexico, seldom subjected to any prelinunary treat- ment, with the exception of grinding; but in the case of highly- pyritous ores, they are sometimes partially roasted, for the purpose of removing the excess of sulphur. At Zacatecas, certain kinds of ore, after being broken into small lumps, are roasted in heaps, by mixing them with wood and covering the pile, which is surrounded by a wall of loose stones, with a layer of charcoal. This operation occupies but 352 SILVER. a few hours, and, after its completion, the ores are ground in arrastres, in the usual way. In the districts of Tasco, Sultepec, &c., where metallic sulphides are particularly abundant, the ores are, after evinding, generally roasted in the reverberatory furnaces employed in the preparation of magistral. The fuel employed for this purpose is wood; but although the roasting of a charge frequently occupies as much as twelve hours, but a comparatively small proportion of the sulphur is thus eliminated. The marmajas, or concentrated sulphides, obtained by washing on the planilla, are also roasted in the same way. Chemical Reactions of the Patio—The general opinion entertained by the various authors who had, previous to Sonneschmid, written on the subject of patio amalgamation, appears to have been, that in the different argentiferous ores, the silver was covered by various substances, such as sulphur, arsenic, and antimony, and that this covering prevented its forming an amalgam with mercury. The salt added to the torta was supposed to possess the property of removing these impurities from the surface of the silver; but this “ clearing action” was thought only to be developed in presence of a sufficient amount of magistral, properly moistened, and which produced this effect through the agency of the heat produced. They also believed that for each mark of silver extracted an equal amount of mercury must necessarily be lost, and that any further expenditure of quick- silver in the progress of the operation was due to mechanical causes. To Sonneschmid, who published his work entitled “Tratado de la Amalgamacion de Nueva Espana,” in 1825, belongs the credit of first presenting a rational explanation of the nature of the reactions which take place during the process of patio amalgamation. This author, who, from his knowledge of chemistry and his long practical expe- rience, was well fitted for the task which he undertook, refuted by unanswerable arguments the notions which had hitherto been enter- tained; and by means of a close examination on the one hand, of the various phenomena which present themselves during the progress of the operation, and by the aid of the light then recently thrown on the subject by the progress of chemical science on the other, pro- pounded a theory which, with slight modifications arising from a more advanced state of chemical knowledge, is that generally entertained at the present day. According to Sonneschmid, that portion of the silver which exists in the ores in a native state is alone capable of uniting directly with mercury ; and if, in grinding with this metal any ores which do not contain silver in the metallic form, a small AMALGAMATION.—PATIO PROCESS. 350 quantity of amalgam be obtained, it is produced by the action of some substance which in presence of mercury has the property of reducing the silver existing in a state of combination. These com- pounds, as well as the native metals, are susceptible of conversion ‘into “muriate of silver,’ under the influence of “ muriatic acid” liberated by the action of the sulphuric acid of the magistral on a solution of common salt. The muriate of silver thus formed may be destroyed by the addition of alkaline earths, but the silver will then be converted into an oxide which has no longer the property of forming an amalgam with mercury. Further, that as certain metals have the peculiarity of separating others in a state of purity from the acids with which they are combined ; mercury performs this part with regard to silver, by taking from it the muriatic acid by which a portion of it is destroyed, whilst the remainder forms an amalgam with the liberated silver. This reduction of silver by the action of muriatic acid on metallic mercury, together with the direct action of the same on that metal, are the two causes occasioning the loss of quicksilver; the direct action of the acid manifesting itself when- ever it becomes necessary to make a further addition of magistral. The mercury lost remains in the residue, either in combination with muriatic acid, or in the metallic state; the former representing the deficit known as conswmido, and the latter forming that portion of the loss classed as perdida. It will be observed that according to this theory, the salt and sul- phate of copper act only in furnishing the acids which they are respectively supposed to contain, and it remained for future observers, aided by a further development of chemical science, to point out the influence exercised by the sulphate of copper, as well as that of the common salt, as a solvent for the chloride of silver formed. Karsten first called attention to the fact that the addition of ma- - gistral caused the production of chloride of copper, by the aid of which the transformation of the sulphides of silver into chloride is chiefly effected, but without supporting his statement by any con- firmatory experiment. The same chemist also pointed out the importance of the presence of a solution of salt as a solvent for chloride of silver, which is thus brought into intimate contact with mercury, at the expense of a portion of which it is decomposed, thus liberating the silver, previous to its entering into combination with the remainder. About the same period, Boussingault confirmed the statements of Karsten with regard to the formation of chloride of AA 354 SILVER. copper, and proved, beyond dispute, that this salt is abundantly produced during the process of patio amalgamation. The whole of the mercury by which the decomposition of chloride of silver is either directly or indirectly produced, appears to be converted into calomel, since no traces of the higher chloride have ever been ° discovered among the products of amalgamation by the patio. The essential ingredients constituting a torta are salt, magistral, mercury, and sulphide of silver. Salt and the sulphate of copper in the magistral react on each other, giving rise to the production of chlorides of iron and copper, and sulphate of soda. The chloride of copper in its turn acts on the sulphide of silver, producing chloride of - gilver, which is dissolved in the excess of salt added to the torta ; and the silver, finally reduced to the metallic state by a portion of the mercury which is ultimately converted into calomel, whilst the reduced silver enters into combination with the unattacked mereury, forming an amalgam. It has also been shown that the lower chloride of copper, formed by the action of sulphide of silver on the higher chloride, is dissolved in the solution of salt, and acts on another portion of sulphide of silver, also converting it into chloride, which is subsequently reduced by the mercury, and finally converted into amalgam. Boussingault has further proved that the copper of the magistral is ultimately to a great extent transformed into sulphide ; sulphide of mercury is likewise occasionally found in the torta, and has, by some chemists, been supposed to be the result of the action of calomel on sulphide of silver, by which sulphide of mercury on the one hand, and chloride of silver on the other, would be produced. It is, however, probable that this substance may, in many cases, have been formed by the direct decomposition of sulphide of silver by metallic mercury, since it is well known that under certain conditions: this action takes place. Messrs. Bowring and Uslar, both of whom were practically acquainted with the patio process of amalgamation, have contended that chloride of silver is not necessarily formed during its operation; but the various phenomena which they have brought forward in support of this view of the question, appear to be far from conclusive, and are all easily explained by the chloride theory, which is now almost universally received.* . * Some chemists are of opinion that the chlorination of the mercury is, at least partially, effected by the higher chlorides of copper and iron, and that the lower chlorides of these metals, in their turn, assist in the reduction of chloride of silver. AMALGAMATION,—-PATIO PROCESS, CS el a oa sede? Cost and Results of Patio Amalgamation.—The results obtained by this process and the cost of the various operations will evidently depend, not only on the nature of the ores, but be also, more or less, influenced by numerous local circumstances connected with each par- ticular district in which it is employed. Under such circumstances it would be impossible to furnish the various items of expense under any general heading, and we shall therefore give the results of this operation as obtained from the books of some of the most important establishments in which it is employed. reduced in the hacienda of San Joaquin, Guanaxuato, Mexico. TABLE showing the result of 11 tortas of Ore from the Mines of Cata and Secho, * One torta divided into two parts. + Average. he | Silver pas as eg eae No.| Date, 1863. erento Salt. pea Merenty. His Roe set ge Le a | dida.| mido, | B © |" O laa | | | | | mon. qtls. ar. ar. Ibs. marks. | Ibs. | Ibs. Ibs. | 1| May13. | 81 20 | 573 | 95] 3,200} 870] 1) 461] 462/15] 8 2! June9.| 80 02 | 480 [117] 3,100 | 848/196! 436 | 632 | 21] 12 3| July2.| 72 21 | 432 |109| 2,721 | 780/100; 402 | 502 | 23] 10 | 4| ,, 23.| 66 30 | 379 | 93| 2,450 | 634] 43) 335] 378 /17| 9 5| Aug. 14} 67 29 | 306 | 84| 1,936 | 553) 11) 292 | 303 | 22] 10 6| Sept. 20] 75 29 | 329 | 70] 2,529 | 719| 73] 379 | 452 | 25] 9 7| Oct.9 .| 77 07 | 293 | 68| 1,711 | 508 |143; 276 | 419 | 36 | 15 ' gi , 30 .| 57 18 | 285 | 48] 1,920 | 566/117) 299| 416 | 30) 14 9| Nov. 25 | 79 00 | 480 | 60| 2,839 | 816 |151| 427 | 578 | 32] 15 10| Dec.23. | 80 12 | 400 | 56! 2,548 | 736 | 96] 403 | 499 | 38 | 16 11| Jan.14. | 44 28 | 270 33 | 2,238),|1,251 | 31 361 | 392 | 32] 15 mi. 24.1 36 30 | 216 | 32; 1,818) | 36; 293 | 329 | 38 | 17 821 02 |4,443 | 865 | 29,010 (8,281 (998 | 4,364 | 5,362 | 271/124) “SILVER. ‘aryseIre oyy UT ATMoLOW YIM Surputss Aq pourergo st Yor syRyour *JU90 Jed g0.6 SBM IOATIS JO SSO] OTL, ‘pahordua som wobjnwun waddoo 303.403 asayy fo a,0yYM 94} UT ‘ZO 98.01 IOATIS JO yrem rod AmMo10W JO ssoy TeOJ, “gueo sod FF.g Bprpsz9d Ammoiow Jo ssory “1eddoo Jo “quae tod 0g ‘Terqsisvut 944 suliedeid roy posn ‘ero teddoo oy pue { uMIpos JO oprt -oTyo Jo queso zod GS Jnogs’ peurezu0) poso[due 4yVs eMLL ‘quad dod 79 = poulryqo ploy “poppe sv tuesTeue | eules vy} JO atom euros ‘1eddoo Utozy oAIT PUNOF SVM I y OUT} Yous pue ‘ weseue taddood Jo’sq, OT UJIM pesuvyo 7% a1IM SBILO] VSO SUIPUILS LO] pasn Satgsvasle dy} JO OMY, | *poureyqgo SBM P]OS 9U4 JO \ ‘quad Jed S1p pue ‘uresyeure IOATIS JO "ST F UIIM posieyo 919M S¥IIO} OSIY} SUIPULIS LOJ posn sorjsvite vy} JO OMY, snorerid oy} jo uorjsod yeyy st vdswy ou, x g8. 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EFL 70 969 | 8 19.886 F 68-209 |66-161°9 66-6ZL'3 |09-66'S \OEG'TS |8G-68L 40 «9TL | 2 L1.100'9 G6-STL |BT-188°9 | **"°""** | BG. 2GL% |09-8Z1L'F |969°FS |FL-616 go 169 | 9 69. 901F 00-869 |69-G3I'S | “*°"""* | LT-OFS |B¢-G0L'S |GOL“9T |98-299 co «129 | G TG. L63°¢ 29.889 |08-699°9 19-6F9‘°S |61-F31'F |606‘SE |Z6- 88 C0 S20 0% SL€1¢ 9 GI-08L |G3-Z4T'4 | “""""""* |SL-FI8'S |F0-898'F |208°6E /26-666 | FO 8IL | 8 6%- 180° 9%. 8F8 ; “eet 1OT.F8TS |P9-861 F |GL9°GE |18-610T | IL 8h4 | & GL-L96 4 06-698 |ZF-666°L 88-Z81‘E |F9-918°h |LI8‘Sg |8G-820'T | SL O22 | T “SIBTLOp ‘suTvIs “SYIBVUL “SIB[[OP | *SAIB[][OP] “SIeT[OpP | “S&LBl_LOp “SuIeIS “SYAVUL | ‘SdlB “SBBIBO ‘ON ‘nea |‘pfog | -aoatig | ‘Teiog, |,"edsey|‘Suryzom! ‘sorq | PIOD | “2°ATIS 756) TPAOL "| . Sururequog ‘aonaoug ‘SLSOQ ‘STILIENVAY ‘oolna Ty ‘oyonapunns COST Us pay1om $0j}10) [1 f0 znsaL 04) burmoys “ponunjuocs ‘INANALVLY AMALGAMATION. PATIO PROCESS. 357 TABLE showing the results obtained at the Hacienda N ueva, belonging to the Fresnillo Company, during the years 1840, 1841; and including the first nine months of the year 1842.* Date. Montones. Silver. Value. Cost of Treatment. marks. OZ. dollars. | dollars. 1840 31,995 147,851 3 1,293,675°12 664,274:13 1841 35,291 | 222,022 0 | — 1,942,692°50 731,346°90 9 months ; | ae | ; : of 1842 28,324 a Greg Os: 1,464,552°50 504,460°50 95,610 537,250 6 | $4,700,92012 | $1,900,081°53 \ These 95,510 montones = 85,366 tons of ore, produced 537,250 marks of silver, about 3,974,000 oz. troy; which gives a mean produce obtained by the process, of 0°0U14 of the weight of the ores operated on. The cost of treatment, per monton of 2,000 Ibs.; the cost per monton, exclusive of the value of mercury expended ; the average loss of mercury ; and the average yield of silver, were as follow :— Total Cost of Treatment, Tre Tiaes ret bere Ounces of Mercury lost, | Mean Produce of Silver including Mercury. nt Mer cury. per mark of Silver. per Monton. Date. dollars. dollars. ounces. marks. 02. 1840 20°76 14°45 14°064 4 5:00 1841 20°72 13°46 12°312 G6 2°25 9months |) ,- “ . 17°02 11°75 11°875 5 7°25 of 1842 ; : Mean result of Patio Amalgamation at Real del Monte, 1864-5} :— Regla hacienda, reducing yearly . . . «. . ~- 51,300 cargas. Loreto me -¢ A Te Pie of Wee so ON ae oe Total yearly. . . . + 105,730 cargas. Mean assay of ore thus reduced . . . . 15°5 marks per monton. Mean produce. . . .. «.. ~~ ~ 4141, or 9:0 per cent. loss. The mean cost of reducing these ores was— Coarse crushing in dry stamps, and subsequent fine grinding in arrastres . . . . . 1°'9 dollars per monton. Manrpulation:in Patiow ~- 20. 0s. so 1 4Oe Ss, - General expenses of management. . . . . 12 ,, % aOR S MC Oe SO kin dee, eter ste ie nc kenge oy) i —— 88 Sulphate of copper (2 dols. per monton) . . . . 32- Salt (1°6 quintals per monton) . . . . . . + . 695 Quicksilver (11 0z. per mark, silver) . . . . . . 6°9 Total tre no UL * From Duport. + Furnished by Mr. Buchan. + At Loreto, to this must be added the cost animal power in grinding. 358 SILVER. Ore from Ophir Mine, Comstock, worked at Ophir Works, Washoe. Average cost per ton of working during eighteen months, ending June 1864. Patio From December 1st, 1862, to June 1st, 1864.* 4 Ep @ B mt Labour. Wood. | Salt. [goa 8 z E zZ 2 = | 6.) 8) 3) dollars. | dolars. | dollars. | dollars. dollars. | dollars. | dollars. | dollars, | dollars. Crushing . 2°68 | 1°85 Ree As ens 0°85 | 0°22 ae 5°60 Beneficiating 3°82 | O19 | 5°95.) 05 | 2°85 | 3... | 007 1156 ee Washing np. 1 az 6 a Ok 0° Oh Ob KO 0) ie 0°02 oe 2°66 Total Cost . | 7°98 | 2°13 | 612 | 0°65 | 3°65 | 0°85 | 0°31 | 1°56 [23:25 AMALGAMATION BY Hor ProcEss.—This process for extracting silver from its oresis much less employedin Mexico than in some portions of South America, where the ores are more generally found suitable for this method of treatment. The only ores which can be advanta- geously worked by this process are such as contain a large proportion of native silver, or in which that metal occurs in the form of chloride, iodide, or bromide. The ores worked in the cazo are almost invariably of the descrip- tion known as colorados, which are, generally speaking, coloured red by an admixture of oxide of iron. These, after being roughly stamped in the usual way, are subsequently treated in the arrastre, but, as they are afterwards concentrated by washing, care is taken not to carry the grinding to such an extent as would cause a large portion of the finely-divided silver ore to be éarried off in suspension by the water. This concentration is effected by means of the inclined plane, called a planilla, before mentioned as being employed for treating the residual matters resulting from the washings of the torta in the patio process of amalgamation. by this means the ore is reduced to about two per cent. of its original weight, and the lighter portions, thus ‘removed by water, may, if found sufficiently rich, be subsequently treated by the patio process. : The cazo is a vessel formed either of curved blocks of stone, or of wooden staves, like those of a barrel, and of which the bottom is made of copper. The dimensions are usually as follow :—diameter at top, 3 feet, * Furnished by Mr. W. W. Palmer. AMALGAMATION.——HOT PROCESS. 359 3 inches; diameter at bottom, 2 feet; depth, 18 inches. The bottom, which, as before stated, is of copper, has, when new, a thickness of 21 inches, but becomes gradually thinner by use. This is retained in its place by a groove running around the interior of the vessel, near its lower extremity ; all the joints being carefully luted with clay, with which the sides of the apparatus are thickly plastered, and which is kept in its place by an exterior wall of unburnt bricks. The copper bottom of the cazo rests on the wall of the hearth, thus forming the roof of a fireplace which has neither fire-bars nor chimney ; and is provided with but one opening, which serves, at the same time, for the introduction of the fire, and the escape of the products of com- bustion. The fire is lighted, and a sufficient amount of water poured into the vessel to form, with the ore subsequently added, a very liquid paste. When the temperature of this mixture has reached the boiling point, and it has become strongly agitated by ebullition, salt is added, in proportions varying from five to ten per cent. of the weight of the ore operated on. It is, however, necessary not to intro- duce the salt until the contents of the cazo are in active ebullition, since it would otherwise form, with the ore, a compact mass, adhering firmly to the copper bottom, from which it could not be removed without emptying the apparatus. As soon as the salt has been added, a workman, who squats on the side of the cazo, continually stirs its contents by means of a wooden agitator, with which he constantly rubs the copper bottom; and at this stage the first addition of mercury is made. The amount of that metal employed is carefully regulated according to the richness of the ore under treatment, and should never exceed twice the weight of the silver it contains. At first, one-fourth only of this quantity is added, and, about a quarter of an hour after its introduction, the workman takes a sample, by means of a bullock’s horn attached to a wooden handle, with which he scrapes the bottom of the boiler so as to obtain a small quantity of the heaviest portions of the ore and amalgam. By washing this in a horn spoon, he afterwards removes the lighter con- stituents of the mixture, and exposes the amalgam, which, if the operation is progressing favourably, should present the appearance of finely-divided granules, of a light lead-grey colour. The amalgam in this state is called polvo, and it is known by experience that it then contains one-third of its weight of silver, or, in other words, that about two parts of quicksilver are united with one part of silver. More mercury is subsequently added, and other samples taken, 360 SILVER. until it is found that the hardness and state of division of the amalgam begin to change, when the operation is considered to be terminated ; but, before stopping, the workman makes another trial, called a prueva en crudo. For this purpose he washes a portion of the amalgam in such a way as to entirely remove all traces of mineral, and, after adding a little clean mercury, and rubbing the mixture with his fingers, he observes whether the quicksilver thus added becomes solidified. Should this be the case, he introduces a further portion of mercury, and continues the operation ; since he has thus learnt that this metal has not been added in sufficient quantity to extract the whole of the silver which the process is capable of affording. When, on the contrary, the mercury introduced retains its fluidity, the liquid contents of the cazo are dipped out into reservoirs, whence they are subsequently removed, to be added to the ingredients of a torta ; whilst the solid deposit of ore, which contains the amalgam, is stored in wooden cisterns, from which it is afterwards taken, for the purpose of being washed in large bateas. Before washing this deposit, an amount of mercury is added to it nearly equal to that which has been employed in the cazo, in order to produce a less dry amalgam, which, becoming united in a mass, is no longer so liable to be carried off in suspension with the mineral and earthy residues. The exact con- sistence which should be given to this amalgam, in order to avoid loss, is a matter of considerable importance, since, if too dry, a portion of it is readily carried away by the water; if, on the other hand, the amalgam be subjected to the process of washing in a liquid state, it is liable to be projected over the edge of the batea by the oscillation necessary for the removal of the various metallic sulphides with which it is more or less mixed. The cazo, which is the apparatus described by Alonzo Barba as that employed in his time for the amalgamation of silver ores, by the aid of heat, has, in the district of Catorce, been much enlarged, and, under the name of fondon, is extensively employed in some important metallurgical establishments. The diameter of the copper bottom of the fondon varies from 5 feet 6 inches to 7 feet 6 inches; and, instead of the necessary friction being produced by the action of a wooden stirrer, worked by hand, it is obtained by means of an upright shaft, provided with cross-arms, to which are attached rectangular blocks of copper, set in motion by a mule, harnessed to a prolongation of one arm. This apparatus may therefore be regarded as an arrastre, in which the paving and stone voladoras are both replaced by metallic copper; and beneath AMALGAMATION.—HOT PROCESS. 36] the bottom of which is a fireplace, similar in all respects in its - construction to that built below the ordinary cazo. In one of the sides of the fondon is an orifice on a level with its bottom, which, during the working of a charge, is closed by a plug; the removal of which allows its contents, both liquid and solid, to be drawn out into tanks, in which the heavier matters are allowed to settle, previous to being washed. , The weight of the charge, which for the cazo seldom exceeds 100 Ibs., is in the case of the fondon increased to from 1,200 to 1,500 lbs. The time necessary for working this amount is six hours, being the same as that employed to work 100 lbs. in the ordinary cazo. The fuel employed consists of the wood of the palm-tree, which, from its small density, burns rapidly, and produces a large amount of flame. The amalgam obtained by washings is treated precisely like that resulting from the patio process ; but the silver produced in this way invariably contains a little copper, which, at Catorce, is removed by cupellation with lead, in a furnace called a galeme. The slimes separated from the amalgam by washing are, together with the residues from the cazo, treated by the patio process. In order to prevent adherence of the mercury or amalgam to the copper bottom of the apparatus, the workmen take care to always employ a less amount of quicksilver than would be necessary to form an amalgam with the whole of the silver present ; but this is of com- paratively little importance, since the whole of the residues of the operation are re-treated in the way above described. By this process, the silver existing in the native state, as well as the chlorides, iodides, and bromides of that metal, is readily reduced ; but this is not the case with regard to the sulphides, and it con- sequently becomes necessary, in order to obtain the silver which they contain, to have recourse to the supplementary treatment by the patio. In working such residues, however, the addition of magistral is not required, since they contain a sufficient amount of chloride of copper to convert the whole of the sulphides of silver into chloride. The loss of mercury experienced during the treatment of silver ores in the cazo or fondon is extremely small, as at the close of the opera- tion a weight of amalgam is obtained which, deducting the silver it contains, corresponds with the quantity of mercury originally em- ployed; but this amalgam, in addition to silver and mercury, contains a little copper, and the total loss, which is purely mechanical, may be taken as being between two and three per cent. oO: SILVER. By this process, the chlorides and other analogous compounds of silver are evidently not reduced, as in the patio, by the action of metallic mercury, but by the copper furnished by the bottom of the apparatus ; and even if it be admitted that this reaction gives rise to the production of the higher chloride of copper, which has, under certain circumstances, a chlorinising action on mercury, this could not take place in the presence of the excess of metallic copper furnished by the bottom, which would at once transform into the lower chloride any of the higher chloride of copper which might be produced, If, in treating ores by this process, the quantity of mercury added be so great as to be attended with the adherence of the amalgam to the copper bottom, the operation is found to proceed very slowly, and a great loss of mercury is the result; as, under these circumstances, the chlorides, iodides, or bromides, present in the ore, being cut off from direct contact with the metallic copper, are reduced at the expense of quicksilver. The most important condition necessary for the economical working of the cazo is to keep its bottom constantly free from any adherence of quicksilver or amalgam; and when the amount of mercury added does not exceed twice the weight of the silver present, there is no danger of any inconvenience arising from this cause. With even twice this amount of mercury, Duport states, he was enabled to work without inconvenience; but the moment that proportion was exceeded, the amalgam attached itself firmly to the copper plate, and a large loss of mercury was the result. Although this process of amalgamation is only adapted for the treatment of colorados, which contain chloride and other analogous salts of silver, it has sometimes been applied to the reduction of the negros, in which the silver exists in the form of sulphides. Under these circumstances, it becomes necessary to make an addition of magistral, which causes a most destructive action on the mercury present, and which is, apparently, not modified by the presence of the bottom of metallic copper, since this loss of quicksilver often exceeds four times the weight of the silver obtained. At Catorce, the poorer ores, after being previously concentrated by the planilla, were, according to Duport, in 1843, treated in the cazo, at a total cost of one dollar six reals per carga of 300 lbs. The richer class of ores, on the other hand, which it was not neceés- sary to wash, but which required fine grinding and great care in working, was operated on in the fondon at an expense of two and a half dollars per carga. : AMALGAMATION.—ESTUFA PROCESS. BLAS. The loss of mercury was estimated at two per cent., and the silver obtained contained about one per cent. of copper. EsturaA AMALGAMATION.—In some of: the colder and more humid districts of Mexico, a modification of the patio process has been em- ployed. The ground ore, instead of being exposed in the open air, on a paved court-yard, as in the ordinary patio process, is placed under a shed, and the usual method of patio amalgamation proceeded with, until the operation is about half completed. The ore is then removed into a sort of room, termed an estufa, or stove, which has under it a fireplace, six or eight feet long, so connected by side flues with small chimneys as to elevate the temperature of the room containing the ore. Here it is exposed to a gentle heat, and allowed to remain during two or three days, when it is again removed, and the reduction completed by the ordinary method of patio amalgamation. By this process, the time required for the reduction of the ore is less than by the patio, and the yield of silver greater; the loss of mercury, on the other hand, is more considerable. CHAPTER XVII. TREATMENT OF SILVER ORES BY AMALGAMATION—BARREL PROCESS. | FREIBERG—BARREL AMALGAMATION—WHEN INTRODUCED—COMPOSITION OF ORES —CHLORINATION—AMALGAMATION—DISTILLATION OF AMALGAM—REFINING—* CONSTANTE—GRINDING CRUDE ORES—CALCINING WITH SALT—SIFTING AND GRINDING—AMALGAMATION AT CONSTANTE— TREATMENT OF AMALGAM—MELT- ING AND REFINING—TREATMENT OF RESIDUES—COST OF TREATING ORES AT CONSTANTE—COST AT REAL DEL MONTE—THE BARREL PROCESS IN NEVADA— METHOD OF CONDUCTING, AND COST OF OPERATION, THE first works erected in Europe for the treatment of silver ores by amalgamation appear to have been those described by Schliiter as having been put up at Kongsberg, for the purpose of treating the stamped ores of that district. This apparatus consisted of eighteen small cylindrical vessels, arranged in a circle, in which the ores were mixed with mercury and kept in a state of constant agitation by means of a vertical spindle in each tub, the whole being worked by a large horizontal toothed wheel placed in the centre. It was not, how- ever, until the latter part of the century that the attention of mining engineers on the continent of Europe became particularly directed to the process of amalgamation. In the year 1780, the Baron de Born suggested to the Austrian Government the propriety of adopting this system in the mining districts of Hungary; and, at his solicitation, some experiments were instituted at the Glashiitte Works near Schem- nitz. Although these trials were not followed by the introduction of this system of amalgamation into the Hungarian mines, they, never- theless, gave rise to many valuable discoveries, of which the Saxon Government, which had deputed a commission to attend on De Born, availed itself in the erection of the works at Freiberg. FREIBERG.—The first works were erected at Freiberg in the year 1790, under the direction of M. de Charpentier, but these were destroyed by fire shortly after their completion. The existing amal- gamation works, commenced immediately after the destruction of AMALGAMATION.—BARREL PROCESS. 365 the former, were completed in 1794, and finally closed about the year 1856.* The amalgamation of silver ores was perhaps at one time more economically conducted at the Halsbriicke works, in the vicinity of Freiberg, than in any other European establishment. Composition of Ores—The usual constituents of the ores treated, were sulphur, antimony, arsenic, silver, copper, lead, iron, and zinc, which were more or less mixed with various earthy minerals, besides sometimes containing traces of bismuth, gold, nickel, and cobalt. In selecting these ores, they were so assorted as not to contain above four per cent. of lead or one per cent. of copper, as from combining with the mercury added, these metals gave to the amalgam produced a spongy consistency, and thereby rendered the treatment difficult and expensive. The different ores selected for amalgamation varied in produce from 15 to 200 oz. of silver per ton, and formerly the mixtures were so arranged that the charges of the furnaces should contain from 75 to 800z. per ton. Latterly, however, it was usual to work the poorer and richer ores separately, as it was found that the loss of silver in the residues was thereby considerably diminished. The mixtures of the poorer ores afforded, on an average, from 30 to 400z. per ton, whilst the amount of silver in those of the richer ores varied from 90 to 130 0z. per ton. It is essential that all mixtures of ores should contain a certain proportion of sulphide of iron for the formation of sulphates, the presence of which is neces- sary to the success of the operation of roasting: the quantity of sulphide of iron present should, generally speaking, be about twenty-five per cent. If the amount of pyrites naturally occurring in the ores was not equal to this proportion, addition was made either of that mineral, or of crude sulphate of iron. Sometimes, however, the ores at Freiberg contained more iron pyrites than was necessary to the success of the operation, and in such cases it was found advantageous to subject the more sulphurous of them to a preliminary roasting without addition of salt, and thus reduce the average amount of sulphur in the mixture to the right proportion. Chlorination. —The’ ore, properly selected, was laid on a large floor forty feet in length by twelve in width, and on the top of it was * The ores formerly treated at Freiberg by amalgamation are now, to a great extent, smelted with galena, and the silver extracted by crystallisation and cupel- lation. 366 SILVER. thrown about ten per cent. of common salt, let down from an upper room by means of spouts placed in the floor for that purpose. The heap thus made up of alternate strata of ore and common salt, was well mixed, by being carefully turned over, and then passed through a coarse sieve. It was subsequently divided into small parcels or charges, weighing from 44 to 5 ewt. each. The salt-employed for this purpose was supplied by the Prussian salt mines. The mixture of ore and salt was now roasted in reverberatory furnaces, provided with fume flues for the reception of the pulverulent matters mechani- cally taken over by the draught. The prepared charge had now to be spread on the bottom of the hearth and gently heated, for the purpose of expelling the moisture, which, to a greater or less extent, it invariably contained. During the process of drying, usually occupying from twenty to thirty minutes, the charge required to be kept con- stantly stirred with a long iron rake. ‘The lumps formed during this operation must also be broken down by means of a beater ‘provided with a long iron handle. On the temperature being subsequently raised, white fumes were given off, and in about two hours from the commencement, the whole mass had become redhot. The charge was likewise occasionally turned, so that every particle of ore might be equally exposed to the action of the fire, and during the whole time the mass required to be diligently stirred with the rake. The fire was then left to burn down, and the combustion of the sulphur promoted by constant stirring. This went on without intermission, until the interior of the furnace had become dark red, and a sample taken from the mass no longer evolved any odour of sulphurous acid. During this process the ore increased considerably in volume, and the particles cohered so loosely together as to offer but little resistance to the movements of the rake. ; After this the heat was again raised during about three-quarters of an hour; the sulphate of iron, formed by the oxidation of pyrites, thus reacted on the common salt, causing, in the presence of peroxide of iron, the evolution of chlorine and hydrochloric acid gases, which, coming in contact with the sulphides of silver, rapidly converted them into chlorides. Chlorides of the other metals present were at the same time formed, together with sulphate of soda. When this roasting was terminated, the charge was raked from the furnace into an iron barrow and removed to an adjoining floor. The ore was subsequently raised to an upper story for the purpose of being passed through a set of sieves, with the view of separating the finer AMALG AMATION.—BARREL PROCESS. 367 powder from the agglutinated lumps. The latter were broken down to a proper size, and a portion re-roasted, by adding a small quantity to each of the subsequent ordinary charges. ‘The remainder was mixed with from two to three per cent. of salt, and calcined in the usual way. The finer particles, which passed through the sieves, were, on the contrary, ground between heavy millstones, by which they became reduced to the state of an impalpable powder. * After roasting, the ores, besides various earthy salts, chiefly consisted of peroxide of iron, basic sulphate of iron, the chlorides of iron and copper, and a certain proportion of oxide and sulphate of copper, sulphate of lead, oxides of antimony and zinc, and a small quantity of various metallic sulphides in addition to sulphate of soda, and the excess of common salt employed. The different compounds of silver originally present in the ores were thus converted into the chloride of that metal, with the exception of traces of metallic silver, and perhaps, also, of minute quantities of sulphide and oxide of silver. The charge suffered in roasting a considerable diminution in weight, generally amounting to about ten per cent.; this loss being chiefly due to the escape of sulphur, chlorine, and the volatilisation of common salt, zine, antimony, arsenic, and the chlorides of iron and copper. Amalgamation—The amalgamation of the roasted ores was at Freiberg conducted in twenty wooden casks, arranged in four rows, and turning on cast iron axles secured to the ends by means of bolts. These barrels, which were internally two feet eight inches in length, two feet eight inches in diameter at the ends, and two feet ten inches in the middle, were made of pine wood three and a half inches in thick- ness, and strengthened by iron hoops and binders.f— On one of the ends of each tun was placed a. toothed wheel working in a pinion keyed on a shaft receiving its motion directly from a water-wheel. The general arrangement of these barrels is represented, Figs. £7, 48. Above each of the tuns so arranged, was placed a wooden box ¢, Fig. 47, into which was thrown the roasted ore. At the bottom of this was a spout terminating in a hose /, made of strong canvas, finishing with a cylinder of tin plate, for the purpose of introducing the powdered ore into the different barrels B. Each * The crude ores were not crushed at the works, but ut the mines, where they were often enriched by mechanical treatment. + At Constante, and at the different works in Nevada, the barrels are perfectly cylindrical in form. 368 SILVER. vask was furnished with a circular opening a, five inches in diameter, fitted with a wooden plug, through which was bored a smal] hole Rie A7: i ae TTT i AMALGAMATING BARRELS. (Sectional Elevation.) Fic. 48. (ee AMALGAMATING BARRELS. (Plan.) provided with a pin, made of hard wood, for the purpose of running off the argentiferous mercury at the termination of the process. AMALGAMATION.—BARREL PROCESS. 369 Below the tuns, and a little above the level of the floor, were placed triangular troughs destined to receive the residual matters at the termination of the operation. Before charging the barrels, 3 cwt. of water were run from the vessels E, exactly holding that quantity, into each; after which 10 cwt. of finely-ground and sifted ore were introduced through the hose #. Each cask should also contain from 80 to 100 lbs. of wrought iron, cut into fragments of about an inch square and three-eighths of an inch in thickness, which, in proportion as they become dissolved by the action of the substances with which they are associated, require to be replaced by fresh pieces. As soon as the barrels had been charged, and the bungs firmly secured in their places by binding screws, the apparatus was thrown into gear, - by a screw acting on a sliding pillow-block, and made to rotate with a rapidity of from twelve to fifteen revolutions per minute. At the expiration of two hours the barrels were in succession stopped for the purpose of examining the state of the metalliferous paste which they contained. If the charge was too firm, a little water was added; but if, on the contrary, it was too soft, a small quantity of ore was intro- duced. When this had been attended to, five cwt. of mercury were drawn off into each cask, and the tuns, after being securely closed, again thrown into gear and kept constantly revolving for about six- teen hours, at the uniform rate of thirteen turns per minute. During the first eight hours of this period they were, at Freiberg, twice examined for the purpose of ascertaining whether the paste was of the proper consistence; for if too thick, the mercury becomes very finely divided, and if too thin it remains at the bottom, and does not become sufficiently incorporated with the various constituents of the charge. In the first case it is necessary to add a small quantity of water, and in the second a little roasted ore. After the introduc- tion of mercury, the temperature becomes considerably raised by the chemical changes constantly going on, so that, even in winter, it sometimes reaches 104° Fahr. At the expiration of eighteen hours the amalgamation was in this establishment ordinarily complete, and the tuns were then filled with water, and again made to revolve, during from one and a half to two hours, with a velocity of only six or eight revolutions per minute. By this means the mercury was separated from the slimes with which it was mixed, and became collected in one mass at the bottom of the tuns. When this union of the globules of mercury had been accomplished, the different casks were successively thrown out of gear, and stopped BB 370 SILVER. with the apertures uppermost. The small peg in the bung was now removed, and in its place was inserted an iron pipe, to which was attached a small hose with a screw and clasp, for the purpose of closing it when required. The cask was then so turned that the plug should be immediately over the spout 0. The hose being put into the iron tube p, the mercury was allowed to run off into the gutter v, by which it was conducted to a receiver prepared for that purpose. This period of the operation was closely watched by the workmen, who, the moment any of the earthy matters began to flow from the orifice, at once closed it tightly. The barrels were now turned with the aper- tures a upwards, the small hose plug removed, and the large bung loosened by a few taps with a mallet. The barrels were subse- quently turned mouth downwards, the bungs withdrawn, and the . muddy residuum discharged into troughs situated immediately under them, from whence it flowed into large washing vats, or tinas, placed on the ground-floor below the barrels. In the course of fourteen days 180 tons of mineral were treated in this establishment, every ton of which required ‘an expenditure of 3 Ibs. of metallic iron, and 8°95 oz. of mercury, so that’ every pound of metallic silver pro- duced was obtained at an expense of 723,ths of an ounce of quick- silver.* The loss of silver experienced amounted, on an average, to from seven to nine per cent. of the total amount present, as indi- cated by assay, but the latter figure may be taken as most nearly approximating to the mean result. During the first two hours that the casks were set in motion, before the introduction of mercury; the chlorides contained in the roasted ore were thus reduced to the state of minimum chlorination, the saline matters dissolved by the water present, and the particles of chloride of silver exposed. If, instead of this, the mercury had been imme- diately introduced into the barrels, it would, by reacting on the sesquichloride of iron, &e. have become partially converted into calomel, which not being again reduced, during the subsequent stages of the operation, would have resulted in a considerable loss of that metal. This loss is, however, avoided by the action of metallic * Winkler states the loss of mercury at Freiberg to have averaged during five years 1°41 loth, or 3 ounce nearly per centner of ore, assaying 3 to 33 oz. of silver ; and 3°57 loth, or 1} oz. per mark of silver produced. Subsequently, however, a great reduction in the loss of mercury was effected. In 1853 the amalgamation master stated the loss was then scarcely 4 0z. per mark. We cannot, however, vouch for the accuracy of this assertion, and our own experience would lead us to somewhat doubt its correctness. a i AMALGAMATION.—BARREL PROCESS. SEL iron, since the protochlorides thus formed are without action on metallic quicksilver. The chloride of silver contained in the roasted ores is, in the Freiberg process, decomposed by agitation with metallic iron, the chlorine combining with it to form protochloride of that metal, whilst the reduced metallic silver becomes subsequently dis- solved in mercury. The chlorides of lead and copper which may be also present, are reduced at the same time as the chloride of silver, and enter into the composition of the amalgam produced. Treatment of Residues.—The residues conducted to the washing vats betore mentioned, were mixed with an additional quantity of water, and kept constantly stirred by agitators attached to iron arms worked by an upright shaft in the centre of each vat, which received its motion from a small water-wheel. These vats were furnished with openings, at various distances from the bottom, through which the tailings, held in suspension by the water, could be successively drawn off into tanks, in which they were allowed to settle. When these residues contained more than four and a half ounces of silver per ton, they were removed to a drying floor, and subsequently re-roasted with from fifteen to sixteen per cent. of iron pyrites, and from five to six per cent. of common salt. These calcined residues were sifted in the usual way, and then, without being re-ground, subjected to amalga- mation in barrels for a somewhat shorter period than was customary in the case of ordinary ores. The mercury collected in the bottom of the different washing vats was drawn off every five or six weeks, and from the large proportion of base metals which it contained, it was treated apart from the ordinary amalgam produced in the usual manner. The mercury and amalgam obtained by tapping the barrels, were afterwards filtered through close canvas bags in the ordinary way. The amalgam which was retained in these bags consisted of a mixture of six parts of mercury and one of an alloy composed of about eighty per cent. of silver, and twenty of a mixture of copper, antimony, zinc, lead, and some other metals. Distillation of Amalgam.—The amalgam, after being well pressed, was subsequently heated in iron retorts placed in suitable furnaces, and the mercury separated by distillation from the non-volatile metals which were obtained in the solid form. Three retorts were latterly employed for this purpose, and into each were introduced, on iron dishes, 350 lbs. of amalgam ; usually resulting in the produc- tion of about fifteen per cent. of retorted silver at thé close of the BB2 372 SILVER. distillation, which generally occupied ten hours. The base metals contained in the alloy of silver thus produced, were, with the excep- tion of a certain proportion of copper, removed by a process of refining in a large iron crucible, which was conducted in the fol- lowing way, Refining.—The crucible was first placed in the furnace and made red hot, when the lumps of silver were successively introduced and: brought to a state of fusion. Powdered charcoal was then thrown on the surface of the fused metal, and the crucible temporarily covered with a thin plate of iron. This, after the lapse of a few minutes, was again removed ; and the impurities which had risen to the surface, were, together with the unconsumed charcoal, skimmed off by means of a perforated ladle. More powdered charcoal was then thrown on the fluid metal, and the scum removed as before. These operations were repeated, with occasional stirrings of the metallic bath, until the surface of the metal had become bright and clean. This process occupied from six to eight hours, and when completed the metal should be malleable and dissolve completely in nitric acid, to which the addition of an excess of ammonia should impart a clear blue colour free from turbidity. The silver was afterwards cast into ingots of a semi-hemispherical form, and in that state forwarded to the Saxon Mint. The dust removed from the furnace flues was, at Frei- berg, after being sifted, mixed with, and treated as, ordinary silver ore. The slags and sweepings from the various melting operations, were crushed and afterwards fused with carbonate of soda and nitre, by which means the silver was obtained in the metallic state. The water run off from the tanks in which the residues from the tinas were allowed to settle, contained, in solution, a considerable amount of common salt and sulphate of soda, together with small quantities of sulphate of iron, and various other soluble salts. BARREL AMALGAMATION AT CONSTANTE, SPAIN.—The ores treated at Constante are obtained from the mines of Hiendelaencina, and contain silver in various states of combination, but principally in the form of antimonial sulphides disseminated in gangues, chiefly consisting of sulphate of baryta, together with a small proportion of quartz, accom- panied by considerable quantities of carbonate of iron, which chiefly occurs in the richer portions of the veins. In addition to the sulphides of antimony, arsenic, &c., in com- bination with sulphide of silver, the ores contain iron pyrites and AMALGAMATION.—BARREL PROCESS. O73 uncombined sulphide of antimony, with small quantities of galena and sulphide of copper. The proportions of these constituents vary, how- ever, with almost every parcel of ore received into the works. The mineral, as delivered at the establishment, is likewise more or less mixed with micaceous slate derived from the rocks in which the lode is enclosed; and the poorer ores usually contain much more of this substance than the richer varieties, to being mixed with which, they generally owe their impoverishment. Immense quantities of such ores, too poor to be amalgamated with profit, were formerly wasted at the mines; but this loss might, to a certain extent, have been avoided by employing a better system of extraction, and greater care in the selection of the ore. Grinding and Roasting Crude Ores.—The ores as they are brought from the mines are immediately taken to cylindrical Cornish crushing mills, and ground and sifted through circular sieves of wire gauze, having ten holes to the linear inch, Each parcel is now laid apart and weighed in presence of two parties ; one of whom is appointed by the mines from which the ores are purchased, the other on the part of the reduction works. As soon as the mineral has been weighed, it is removed to the stores where the several parcels are piled one on another heterogeneously, and from whence the ore is taken as it may be required. The furnaces employed for the calcination of the ores with salt are, at Constante, eight in number; six of them having revolving hearths worked by machinery similar to Brunton’s calciners, whilst the remaining two are hand furnaces of the ordinary reverbera- tory description. The mechanical calciners employed in the establish- ment make from three to four revolutions per hour, and have movable hearths fourteen feet in diameter. Each of these furnaces requires an expenditure of about half a horse power to turn it, and is provided with a single fireplace consuming from 120 to 140 lbs. of pine wood per hour. An improvement on this apparatus has been effected by Mr. W. West, who employs two fireplaces, and thus more evenly distributes the heat over the surface of the hearth. This improved calciner is represented, Figs. 49, 50,in which A is the doorway of the calciner house; B, a window in ditto; c, cast iron hopper through which the ore is fed; and P, three cast iron fluke or agitator frames built in the masonry of the arch. The revolving table E, on which is spread the mixture to be calcined, has a slightly conical surface, and is made of the best firebricks set on end in a cast iron shell. The lining of the furnace F, in which the calcining table 374 SILVER. revolves, should also be built of refractory material. The fireplaces G, are situated on either side of the furnace, after traversing which, the products of combustion make their escape by the flue, H, to the chimney. After calcination, the ore passes through the cast iron spout I, into the chambers J, in which it is deposited. The opening k, beneath the furnace, is for the purpose of allowing space for working the worm wheel and pinion communicating motion to the revolving table. The foot-block, carrying the perpendicular shaft, is supported by the block of stone L, and the furnace is tightly braced by the girders M. Fia. 49. SSS aha det, ee REVOLVING CALCINER. (Vertical Section.) The mixture of mineral and salt is made as intimate as possible, especially for the mechanical furnaces, since in them the charge is but little disturbed by the rakes: they are charged with ore and salt by means of the iron hoppers placed immediately over the centre of each of the hearths. For the supply of the hopper a heap of about fourteen quintals of ore, with from five to six per cent. of salt, is, from time to time, prepared upon the platform on the top of the furnace, and a few shovelfuls thrown in occasionally, as required; taking care, how- ever, always to have enough in the hoppers to prevent the escape of acid vapours through them from the furnace. The time during which the mineral remains in the apparatus, and the quantity calcined per AMALGAMATION.—BARREL PROCESS, eyes hour, must necessarily depend on the rapidity of motion given to the revolving hearth, and the angle at which the iron stirrers are fixed. The average amount passed through each furnace in twenty-four hours is about eighty-four quintals, or three and a half quintals per hour; or for every revolution of the bed, nearly one quintal is discharged from the furnace. Compared with the German roasting furnace, the me- chanical furnaces are found less efticient for the treatment of rich Fig. 50. Gx GY, REVOLVING CALCINER. (Horizontal Section.) ores; particularly when they are charged damp and contain much sulphur, in which case the excessive production of lumps becomes a serious inconvenience. But in the treatment of the class usually brought to the works, they possess the advantage of calcining a larger quantity in a given time, and they require no further attendance than is necessary for supplying them with ore and fuel. ‘The management of the fires is also a matter of importance, since should they be forgotten, 376 SILVER. and the heat become lowered, the mineral, from continuing to pass at the same rate through the furnace, cannot be properly calcined ; and in order to raise the temperature, after having been neglected, the work- men sometimes charge the grate with fuel to such an extent as to overheat the ore. Of the three hand furnaces used.at Constante one is very old, and only employed for drying salt before grinding, and for calcining sweepings, and other refuse matters, containing silver. The other two are similar in form to those of Freiberg, and are worked in much the same manner. They are chiefly employed for the calcination of such ores as contain 9 oz. and upwards per quintal. A charge for these furnaces weighs about 540 Ibs., and consists of about 496 lbs. of dry ore, 40 lbs. salt, and 5 Ibs. moisture. A smaller proportion of salt may be employed in the calcination of very poor ores, but it is seldom less than six per cent.; for the richer minerals it is necessary to add a larger proportion of salt, frequently as much as 15 per cent. When a charge is introduced into the furnace, it is evenly spread over the surface of the hearth by means of an iron rake, and for the space of half an hour scarcely any fuel is thrown on the erate, whilst the mineral is constantly stirred, in order to evaporate the moisture and to prevent the formation of lumps. ‘The fire is then gradually increased, and the ore, which by degrees becomes so heated that the sulphurous matters enter into ignition, is stirred uninter- ruptedly with the rake, so as to expose continual fresh surfaces to the action of the air. The charge is likewise turned, in order to, from time to time, equally expose every part to the action of the fire. After the lapse of about two hours the mineral has become fully heated, when the fire may be left to burn down for about an hour. - It is then again urged for nearly three quarters of an hour longer, so as to cause the sulphates produced by the oxidation of metallic sulphides to react on the salt, which, in the presence of metallic oxides, evolves chlorine, which combines with the silver and other metals present. The whole operation, from the introduction to the withdrawal of the charge, occupies four hours, during which time from 140 to 160 lbs. of wood are consumed. The metallic sulphides, contained in the rich ores operated on in the furnaces, do not amount to more than from 9 to 10 per cent., whilst in the poorer ores the proportion is often con- siderably less. Sulphide of iron is a necessary ingredient in silver ores to be sub- mitted to this process of amalgamation, and during the roasting process AMALGAMATION.—BARREL PROCESS. 377 is oxidised and partially converted into sulphate which, reacting on the salt, evolves the gases necessary for converting the silver into chloride. The proportion of sulphide of iron requisite for this purpose appears to be variable as regards different ores. At Freiberg at least 20 per cent. was considered indispensable, whereas at Constante good results have been repeatedly obtained with only 8 per cent. even when operating on rich minerals. The silver ores of that neighbourhood are but little accompanied by sulphides, and arsenides of other metals, and the pyrites found is very poor in silver and easily oxidis- able. The comparative purity of these minerals may account for their ready calcination, for in the case of ores containing large proportions of sulphides, arsenides, &c., a great excess of chlorine is required for the purpose of effecting their complete decompostion. In the hand furnace, as much as 14 per cent. of salt was formerly added, but with ores containing 9 oz. of silver per quintal 6 per cent, has sometimes been found sufficient. Separating the richer from the poorer ores, and treating them apart, has been found very advan- tageous here, as well as at Freiberg. The calcination of the ores with salt is the most important of the operations connected with this process of amalgamation, as on it, in a great measure, depends the nature of the results obtained from the barrels; since, in whatever way the operation may be conducted, the silver extracted will be com- mensurate with the amount of chloride formed in the furnace, The success of the calcination is, therefore, judged of by the proportion of chloride of silver contained in the roasted ore. This is ascertained at Constante by digesting for some hours a small weighed portion of the roasted mineral with warm dilute ammonia; it is then thrown on a filter, the residue well washed, and finally dried and assayed for silver. It is obvious that the weight of this metal obtained indicates the quantity remaining uncombined with chlorine. Another method, in some respects preferable to the process with ammonia, is to treat the roasted mineral with a strong solution of common salt. For this purpose a few grammes of the calcined ore, just as it is drawn from the furnace, are thrown on a filter upon which is poured a hot saturated solution of salt, until the liquor, which filters through, no longer affords a white precipitate of chloride of silver on being largely diluted with cold water. The residual ore is then dried and assayed for silver, as in the former case. It has been suggested that the crude mineral, which is at present sifted through an eight or ten-hole sieve, would be better if ground a little finer, but a certain degree of coarseness 378 SILVER, is necessary in order that the oxygen of the air and the gases evolved in the process of calcination with salt may become freely diffused throughout the charge. Ifthe mineral be very finely ground previous to calcining, the porosity of the charge is greatly diminished, and consequently the calcination is found to proceed more slowly ; besides which the formation of lumps is thereby facilitated. Fia. 51. - HorizontaL Miuzs. (Constante.) Sifting and Grinding Roasted Ores.—The calcined ores before being submitted to amalgamation in the barrels are first sifted through a circular sieve of sixty holes to the linear inch, and the portion which does not pass through is then very finely ground, in order that every particle of silver which it contains may be exposed to the action of . AMALGAMATION. —BARREL PROCESS. 379 mercury ; the portion passing through the sieve, amounting to 40 per cent, is taken directly to the barrels for amalgamation. The coarser portion of the ore, which is allowed to accumulate in the furnace- house, is, when required, removed and passed between a pair of cylinder mills from which it falls into a revolving sieve of sixty holes to the linear inch; the coarser ore escaping from this sieve is then raised by an elevator, and dropped into the hopper of a second pair of smooth cylinders, from whence the mineral falls into another sieve of the same degree of fineness as the first. The hard coarse particles, which refuse to go through this second sieve, are finally cround in horizontal mills of French burr stones. The arrangement of four of these mills, of which there are eight in the establishment, is repre- sented, Fig. 51, in which one pair of stones is shown in section. Into the circular hopper A is introduced the stuff to be cround; BB are small pipes of sheet iron for delivering the stuff between the surfaces of the runner ¢, and the bedstone c’; D casing enclosing the runner into which the ground material is delivered; E hole in centre of runner; F driving shaft with continuation G for belt pulley; HH’ regulating screws for elevating the runners C ; J driving wheel; K crown wheel; L wheel giving motion to pinions MM’; N vertical shaft for driving supplementary apparatus. Four pairs of stones are driven by the wheel L. The surface of the runner is parallel with the bedstone from the periphery to within one-third of its diameter ; the line of the lower face of the runner then feathers upwards in order to receive the feed. The following particulars afford sundry details relative to this apparatus :— Diameter of stones. . . . . - - 4ft. 2 inches. Thickness of bedstone. . . . . ~ 12 inches. ” fuppor sole? oS Sepsis Gauge of stuff in hopper, about. . . 100 holes to square inch. z Ae OU GAULVEIY fo fog frucy gar 2 > i Number of revolutions . . . . ~. 100 per minute. Quantity of stuff ground per 10 hours. 1 ton per pair of stones. Horse-power employed, about . . . 5 fe Z Revolutions of sizing sieves . . . . 28 per minute. Diameter 7 Ss oe or oO. AnehOS. Length 7 r, yoke we LOO ks No. of holes per sq. inch in sizing sieve 3,600. ‘haracter of runner . . . . . ~ French burr. ‘5 bedstone . , . . . Sompact quartz, moderately hard. Duration ofrunner. . |... % + Average, 18'weeks. e Peuskhoue a. TS ee 5 2D ths When dressed’: 2 oa ab ved» Ae Every third: day. 380 SILVER. In place of fine sifting and carrying the remainder of the cal- cined ore directly to the mills, and there crushing and grinding the whole to a fine powder, it might be desirable to first remove the hard lumps of ore, which are always produced in the operation of roasting, by passing the mineral through a sieve of about the same fineness as that employed in the mills for grinding the crude ores. The lumps, which would be separated from the calcined mineral by the sieve above mentioned, are found to contain a considerable proportion of silver not converted into chloride, which is owing to the circumstance of these lumps being chiefly formed at the commence- ment of the operation, so that the inner portions escape the action of the gases evolved at a later period. These lumps should, therefore, _ be crushed, and submitted to a second roasting, either alone or mixed with the ordinary charges of crude ore. In the hand furnaces a much smaller proportion of lumps is produced than in the mechanical ones, owing to the constant stirring to which the mineral is subjected in the former, | | Amalgamation—The total number of barrels employed is sixty, each being, internally, three feet four inches long, and two feet six inches in diameter. The barrel department is divided into three sec- tions :—No. 1, contains twelve barrels; No. 2, contains twenty-four barrels ; and No, 3, twenty-four barrels. All of them can be driven by water power ; those of Nos. 1 and 3 can likewise be worked by steam. The barrels are placed at a height of about twelve feet from the ground-floor. Immediately over them, and projecting through the floor above, are fixed iron hoppers for receiving the mineral to be amalgamated, which is introduced into the barrels by means of leathern hose, with which the whole of the hoppers are provided. The average weight of a charge for each barrel is thirteen quintals; but the hop- pers are capable of holding a still larger amount. These latter are charged by gangs of men, each of whom carries a sack of mineral, weighing about a quintal. In the barrel-house No. 3 a railway is laid down between the hoppers, by means of which they can be regularly and quickly filled with the requisite quantity of ore. The internal shape of the barrels is, when new, cylindrical; but, after being in use for some time, their dimensions are increased by the wearing away of the inside, near the middle.* * In the amalgamation works of Nevada the barrels are made of 2-inch planks, and internally lined with 4-inch blocks of pine, similar to an internal wooden pave- ment. These blocks are so arranged as to cause the wear to take place across the AMALGAMATION.—BARREL PROCESS. 381 The amount of water introduced into each barrel varies with the nature of the ore, but the usual quantity is about 320 lbs.; and. the iron contained in each amounts to 100 or 150 lbs. Considerable wear and tear of the barrels is caused by using large scrap iron of every kind for this purpose; and its action is less effective than would be the case with iron in smaller pieces. The charge of ore and water having been introduced, the barrels are set in motion, and made to revolve at the rate of from eight to ten revolutions per minute during two and a half hours, in order that the ore, water, and pieces of iron may become completely incorporated. They are then stopped, and the state of the pasty mass examined. If this be too soft, or too stiff, more mineral, or additional water, is added, as the case may require. Should the paste be found of the right consistency—that is, just sufficiently stiff to allow of being formed into a ballin the hand—the mercury is poured in; the weight of that metal introduced being four quintals to each barrel. The loss of quicksilver is rather diminished than augmented by employing large quantities, since its fluidity is less affected by its combination with silver. After the introduction of mercury, the barrels are driven at the rate of from eighteen to twenty turns per minute, for a space of sixteen and a half hours, at the end of which time the amalgamation is considered to be accomplished. The barrels are now filled with water, for the purpose of rendering the paste liquid, and collecting the globules of argentiferous mercury into one mass for drawing off, and kept slowly revolving during a further space of two hours. In dis- — charging the barrels, the mercury is first drawn off into the trough fixed beneath each row of casks, and thence conducted to an iron vessel, in which is collected the quicksilver run off from all the barrels; and any earthy matters which may escape with the mercury are carefully cleaned off the surface with flannel cloths. The fluid metal is subsequently run into canvas bags, which retain the solid amalgam, whilst the more liquid mercury filters through, and is re- ceived into an iron tank, situated beneath. During this operation, which lasts upwards of an hour, the barrels are continued in motion ; because the whole of the residues having to pass through the vessel in which the quicksilver is collected, before they can arrive at the washing vats, cannot safely be discharged until the mercury has been run into the filters. grain, and whenever a lining has become worn out, it can be readily replaced ; the adoption of this form of construction has resulted in a considerable economy. 382 SILVER. The process of amalgamation includes three operations :— 1. The barrels are charged with ore, water, and iron (without any mercury), and made to revolve, at the rate of ten turns per minute, for two hours, or until the mixture has become thoroughly incorporated, and is of the consistency of thick paste. This being accomplished, the mercury is introduced. 2. The casks are immediately afterwards put in more rapid motion, viz. eighteen to twenty turns per minute, and continued at this speed for about sixteen and a half hours; at the end of which period the complete amalgamation of the silver is supposed to have been effected. 3. In order to collect the argentiferous mercury into a mass for drawing off, it is necessary to reduce the consistency of the paste contained in the barrels. For this purpose they are filled with water, and driven slowly, at eight or ten turns per minute, for the space of two or two and a half hours. The amalgam is then dis- charged, and subsequently the residues; the barrels are discharged every twenty-four hours. The average richness of the ores treated may be taken at about 43 oz. per quintal. Treatment of Amalgam.—tThe solid amalgam collected in the canvas bags above mentioned is treated in a very simple form of distilling apparatus, for the purpose of separating the mercury from the silver. The amalgam to be distilled is moulded into a cylindrical form upon an iron tripod supporting a perforated disc, depending from which, and fixed in brickwork, is an iron tube, dipping into a vessel of water placed beneath. Over the cylinder-shaped pile of amalgam is placed either a copper or cast iron bell, and perfect contact with the plate is ensured by carefully luting the joint. A circle is then made with loose bricks, raised around the bell at a short distance from it, and the space between filled with charcoal. The heat afforded by its combustion volatilises the mercury, which is quickly condensed and is collected in the cold water supplied to the cistern beneath. About 2,000 lbs. weight of amalgam are usually operated on at a time, nearly forty-eight hours being required to complete the distillation ; and as many as forty sacks, weighing, in the aggregate, eighty arrobas, of charcoal are consumed during the operation.* As may be supposed from the form of the apparatus, a portion of amalgam fuses, and falls into the cistern below; which, however, may * This apparatus is merely a modification of the Mexican capellina. AMALGAMATION.—-BARREL PROCESS. 383 be readily separated by filtration from the fluid mercury. This gene- rally amounts to 60 or 801bs. in weight. The quantity of crude silver yielded by. 2,000 lbs. of amalgam is generally about 290 Ibs., or 144 per cent. of the amalgam operated on. This silver has a brownish-white colour, is exceedingly porous, and may be readily broken in pieces under the hammer. Melting and Refining—The porous silver obtained from the distil- lation of amalgam is melted, at Constante, in a species of cupola, ealled a cras. When the metal is uncontaminated by impurities which impair the malleability of the resulting bars, the cras may still be employed for melting it, although a loss of silver must result from exposing it, at so high a temperature, to the action of a powerful blast. But when, as is most frequently the case in amalgamation works, the silver to be melted contains matters which impair its mal- leability, the removal of these is readily effected by this apparatus. The amount of impurities required to impart the property of brittle- ness to fused silver is, nevertheless, very small, and chiefly consists of lead, sulphur, antimony, and iron. ‘These bodies may be readily got rid of by cupellation with lead, an operation, however, which, for this purpose, is attended with considerable trouble and expense. Melting the silver in black-lead crucibles appears to be, therefore, preferable. It may be thus puritied by repeated additions of powdered charcoal, skimming and stirring, and be finally obtained in a perfectly malleable state. Instead of employing black-lead crucibles, large iron pots, capable of melting from 500 to 600 marks at a time, were used at Freiberg, and found to answer very satisfactorily. By fusion in large wrought iron crucibles, the silver may be ob- tained free from all impurities impairing its malleability, and ren- dering it unfit for the coining press. Treatment of Residues—The residues, on being discharged from the barrels, are conducted into large vats, in which revolve upright stirrers, fixed on four radial iron arms. The mud is retained in these vats for several hours, and kept in continual movement by the stirrers ; in order that the particles of amalgam, disseminated in the residual matters, may subside to the bottom, and be afterwards collected, a constant stream of water flows into the vats during the whole time ot washing. On being discharged from the vats, the mud flows directly into the river, in the bed of which it accumulates until it is carried off by a freshet. 384 SILVER. COST OF TREATING ORES AT CONSTANTE. Cost of working Mechanical Furnaces— Wood for each furnace per week «© «+ eos 940 rs.* Salt, 6 per cent. 3,528 lbs. at 14 rs. per quintal . 494 Sut WOOD ee es a mle oo Geena 19 Labour foreach furnace =f. 7. 3° 4 oe os 184 Rs. 1,637 Ore calcined per week, 588 quintals in each furnace ; 1637-588 =2'8 rs. per quintal. Hand Furnaces— Each furnace calcines 210 quintals of rich ore per week. consumes 294 arrobas wood . . . . - 294018. 12 per cent. salt=2,520lbs, . 353°0 ” bi) ”? ” ? TARR et nae a Rs. 889°6 8896-210 =4'23 rs. per quintal. Hence cost of calcining in mechanical furnaces is . . 2°8 rs. per quintal. ” he) ”? hand ”? yh 4°23 ? ”? Average cost of roasting, 3°2 rs. Section of 24 Barrels— Wear and tear. . . ss « ay) al Se. a nee 800 rs. Tron consumed, 5 Aa ded Fae s + tae Mercury, reckoning the loss at 53 02. talae wlio of silver, or 454 Ibs. at b°62 rs. | oo. . ee Labour bck aniaet oie ae eee 1,157 Rs. 4,628 Ore amalgamated per week by 24 barrels, 9,352 quintals ; 4,628 2,352=1° 96 rs. Taeidentala) 27) AR ea See re Cost of amalgamating 2°00 rs. per quintal. Summary. Cost of crushing, er Quimtal, soc.6: goo tee 0'95rs. zs calcining ® oy eee eae ase aan ea 3°20 2 amalgamating ,, ies 2°00 aS distilling amalgam, aie ining siti — pare 0°80 Sundry labour and materials... + + + e+ + 3°00 Total, exclusive of salaries, &. . . Rs. 9°95 or about 45s. 6d. per ton for ores containing on an average 44 oz, of silver per quintal. * ‘Reals Vellon = 25d. AMALGAMATION.—BARREL PROCESS, 385 The quantity of ore which 60 barrels will reduce per week is 5,880 quintals. Weight of mineral which all the furnaces will calcine in the eo wiiee eee. ng = . -Ky feel Bl. 4,058 i; Pete eee MeChamiCn LANNaCes: 8. fe ie! aur ei, sete 4 8,528 > Three Hand Pe eh cuca MY. E ion. 05. De0 * These works have consequently the means of reducing upwards of 1,800 quintals of mineral per week more than the present number of furnaces can, when in full work, calcine. Forty barrels would therefore be apparently sufficient to amalgamate all the mineral that can be roasted, but, as the supply of water is irregular, it is advantageous to have extra barrels, so that whilst the calcination is carried on without interruption, the ore accumulated during the dry season may be readily reduced when the supply of water is plentiful. Notes relative to cost, dc. at Constante :— Cost of firewood per 100 lbs., 10d. » mercury per lb., 1s. 2d. including carriage. oe elt pe ba oes. - Average cost of carriage of ore from mines to work, about 3s. per ton. Cost of ordinary labour per diem, 1s. Kstimated loss of mercury per mark of silver, 54 oz. : », Silver per cent. on assay produce, about 12. The length of time a wooden barrel will last in regular work, 6 months. Miller’s wages at horizontal mills, 93d. per ton of ore ground ; cost, including wear and tear, 2s. 3d. per ton. ; At Miner's crushing mill, usual cost, including labourers and wear and tear, about 33d. per ton. The sifting of the calcined ore is done by contract at the rate of 2d. per quintal of fine powder. This fine powder usually amounts to 35 or 40 per cent. of the calcined mineral. REAL DEL MONTE, MEXICO ; MEAN RESULTS OF BARREL AMALGAMATION, 1864-5.* Velasco hacienda, reducing. . . . . . . 107,700 cargas yearly. Sanchez a 3 fe Pe Nit. 28 48.550 r St. Miguel ,, Cahn tha ak. 49-806 : Total reduced in the three haciendas . . 205,850 cargas yearly. The mean assay of the ore thus reduced was 13°0 marks per monton. EMEP AT TOUUCOs oof se kk ls, VES " . Mean loss’ . . . ~. ~~ 1°7, or 13 per cent, The mean reduction cost in the three works was as follows :-— * Furnished by Mr. Buchan. Gc. G 386 SILVER, Grinding by wet stamps . . . . . 2°20 dollars per monton. Drying, sifting, and roasting . . . . 2°75 ,, - . Amalgamation in barrels’ .- 2... VIO, 4 General expenses of management. . . 1°20 ,, me Repairs to furnaces and machinery . . 1°55 ,, ; Total. =. $8"80 Fuel (wood, 21 quintals per monton) . 3°70 ,, a Salt (2 quintals per monton) . . . . 830 ,, ‘3 Quicksilver (4°7 oz. per mark of silver) . 2°80 Total per monton . $23°60 To this must be added, for auxiliary steam-power, Sanchez $2 % s Velasco $3 BARREL PROCESS AS CONDUCTED AT THE OpHtR Works, EIC., Nevapa.— Drying the Ores.—The ore is first dried on a kiln com- posed of twenty parallel flues 12 in. x 12 in., covered by cast iron plates, half an inch in thickness. Crushing.—The rock is stamped dry, in batteries with four dis- charges in each coffer, through brass wire screens of 1,600 holes to the square inch. Roasting—It is then roasted, 1,300 lbs. at a charge, in rever- beratory furnaces 8 ft. 6 in. x 9 ft. in the hearth; salt is added from twenty minutes to an hour and a half after the furnace 1s first charged. The time required to roast a charge varies from 4} to 6 hours; about 43 hours is the average time necessary for second class ores, and the usual quantity of salt added is 5} per cent. One hour before the charge is drawn, from 14 to 8 per cent. of carbonate of lime is added in order to decompose a portion of the sulphates and chlorides of copper, zinc, &c., to prevent loss of quicksilver during the amalgama- tion, and also to produce an amalgam of greater purity. The ore when in the furnace is continually stirred, and is turned three times during the roasting: 1stly, two hours after the furnace is charged ; 2ndly, before the limestone is added; and, 3rdly, when the limestone has been in about 35 minutes. Mr. G. Attwood, the former manager of these works, states that he found, that by a careful addition of lime- stone all the chlorides and sulphates of copper, &c. in excess, can be decomposed. *> | | Sereening—The roasted ore is put through a bolt with a screen of 1,600 holes to the square inch, and then elevated to the barrels. Amalgamation.—The barrels are charged with one ton of ore, and run with water and 450 lbs. of iron during three hours. It is found AMALGAMATION.—-BARREL PROCESS. 387 that with a large amount of iron in the barrels, upwards of 4 per cent. more silver is obtained than with the usual quantity, of 10 per cent., of that metal. From 350 to 400 lbs. of mercury are now added, and the barrels allowed to run, at twelve revolutions per minute, during 12 or 13 hours, when they are filled up with water and drawn off, after being again run for two hours. The amalgam obtained is strained through a stout canvas conical bag, and the tailings washed in a settler 15 ft. in diameter, passing from thence through a series of sluice boxes into a flume about 600 ft. long and four feet wide provided with riffles. The amalgam yields about one-sixth of its weight of bullion, averaging 650 parts of silver in a thousand; the most impure samples assay about 375, and the best 992 thousandths. Distillation —The amalgam is distilled in circular retorts 44 ft. long and 10 in. in diameter, set on an arch of brickwork, with three dampers to direct the flame towards any part where the heat may be ‘required. Returns from Ophir Ores, worked at the Ophir Company's Reduction Works, Nevada, for the Months of June, July, August, September, and October, 1865.* Quantity. Class. - Total Value. tons. lbs. 1,998 1,160 3rd $1.21,512°71 101 940 Ist 49,450°51 2,100 100 $170,963'°22 $81°41 Average per Ton. Returned 130 bars ; weight 11,732 lbs. Valued at . $158,774°20 $75°60 Return obtained. TOBE ole k y's ap oe eel Oas02 7°12 per cent. Total loss of Orickeilver 2, 176 lbs., or 2°96 oz. to each lb. of Bullion. Returns from Ores extracted from Mexican Mine, Virginia City, and Empire Mine, Gold Hill, worked at the Mexican Company’s Mill, at Empire City, in July and Hots 1865. x REE ; Value in Gold. PerTon. Valuein Silver. Per Ton. ons. 5. 137 1,525 $7,585°17 $5506 $12,753°80 $92°58 Bullion produced . . $6,237'°21 $45°27 $12,225°64 $88°74 ; Produce of Gold . . . . . . . 82°25 per cent. A Silvers a. 95°82 Wecaies: Wale OF OTG4 c.- vita: ee 2 _ $20, 338: 97 = $147°64 per ton. » » Bullion . . . . . $18,462'85=$134:02 ,, ,, Produce. ... . . 90°74 per cent. * Communicated by Mr. G. Attwood. cce2 ~ 388 . SILVER. Experiments made by Mr. G. Attwood in order to determine the loss experrenced on the precious metals in the operations of roasting and amalgamation of Com- stock Ores. One thousand pounds of Black “base metal” ore, from the Ophir North Mine, roasted for 44 hours with 5°50 per cent. of salt, and 2°50 per cent. of limestone, | weighed 1,080 lbs. It lost 4°99 per cent. in ae and the mixture gained 3 Ibs. in weight— Assay value, silver . . . . . « . 43°43 . so REORGD. Mirae atten, % 53 . Total 1,000 Ibs., roasted 5} hours with 7 per cent. salt, and 6 per cent. limestone, weighed 1,123 ihe: lost 6 72 per cent. in value, and 7 lbs. in weight. Twenty-one tons of the same ore, after being roasted, assayed Silver, perton « . . . ‘$99°97 Gold D beteaer er 92:80 $192°77 =$4,048'17 value of parcel. Value of bullion returned . . . $3,915°57 Loss in amalgamation 3°27 per cent. The loss experienced during barrel amalgamation is, however, generally greater than the above, as the samples were in this case taken out of the barrels before being drawn off, the amalgam washed out by hand, and the residue dried and assayed. The average loss on working the ores from the Comstock vein in barrels is 13°50 per cent. Ophir ores work better than Savage, Chollar Potosi, &e. Composition of Ores——The following analyses of ores from the Ophir Mine will serve to show the character of the rock usually treated at the different mills in the vicinity of Virginia City. 1st Class. 2nd Class. 8rd Class. Gangue. . 63°38 80°70 95°75 STLVEr Ue ats 2°78 0°89 0°10 Golde os. i 0°05 0°03 0°00 Lead *2 723 4°15 4°04 0°40 Sulphur. 7°95 3°05 1:04 TANG Foss 14°45 551 0°48 . Copper. ._ 1°59 1:43 0°30 TOR Gr Sayre 5°46 3°46 1°55 Antimony . 0°08 trace. trace. 99°89 99°11 99°62 AMALGAMATION.—BARREL EROGCESS, 389 The analysis of an outside chip of a bar of bullion, obtained by barrel amalgamation, from the ores of the Comstock vein, gave the following results :— Come ee. lw ce SD 5B Cipetewuar ay: . we) oe ADI Pen Gmee ee e ee er 8 ee Be oo OL GER es es os Pe LOE RO: se. Ape ws ye OO eC ee ee ee Pl? Tota to 98s eo oe Assay of samples from flues of Roasting Furnaces at the Ophir Reduction Works, August 5th, 1864. Value. No. 1 contained Lead 28°02 per cent. = 5 Silver, per ton 60°l40z. . .$ 78°18 3 - Gold ns Pale. oe! 2b Uk Value . ._.$103°19 No. 2 contained Lead 24°66 per cent. . sf silver, perton ... . « .$122°80 ” ” Gold Pp sthr rey ind © ery = OOO Value . . . $185°43 COST OF REDUCTION OF ORES BY BARREL AMALGAMATION AT THE OPHIR WORKS, 1865. Labour, of every description, perton . . . .$ 9°50 Wood, at $5 percord . . ap teen = Gren) Salt, 4 per cent. at 3 cents. gee Ib. Conavnee bt ig oad? Quicksilver, 1 lb. at 64 cents... irene 0°64 Shoes, Screens, Shovels, Belts, Tools, eon Aen a Castings, Seno Tron, limber ees etsy ote alt ie OOo Charcoal, Assay office Expenses cc. ae on meee tO Total . . . $2014 These ores assayed about $80-00 per ton. Ores assaying over that yield cost from $20:14 to $27 per ton, according to the amount of salt required, quicksilver consumed, and lime employed in furnaces. Each furnace requires four men, two on each shift, as the charge is constantly stirred, and about a cord of wood is burnt in 24 hours.* The usual charge, for $80 ore, is about 1,300 lbs. which is roasted during 44 hours. The chief cost of the barrel process is roasting, labour, and dry stamping. The cost of amalgamation is only about $3 per ton. The cost of labour in Nevada may be taken at $4 per diem. ae * The roasting is conducted in furnaces entirely constructed of ordinary red £ y bricks. CHAPTER XVIII. TREATMENT OF SILVER ORES BY AMALGAMATION—PAN PROCESS. STAMPING — COMMON PAN—VARNEY’S PAN—WHEELER’S PAN—HEPBURN AND PETER- SON’S PAN—SEPARATORS— WORKING IN PANS—RETORTING—ARRANGEMENT OF REDUCTION WORKS—TREATMENT OF ROASTED ORES IN PANS. SHORTLY after the discovery of silver mines in Nevada it became evident, that owing to the prevailing high prices of labour, fire- wood, and other materials, none of the processes employed in other countries for the reduction of silver ores, could be rendered available in that locality for the treatment of rock assaying from $20 to $80 per ton: it, consequently became necessary to have recourse to some method of operating which would dispense with roasting, as practised in the ordinary barrel process, on the one hand; and the frequent manipulation, and great expenditure of time involved in working by the patio, on the other; and to endeavour, by the introduction of direct amalgamation, to work the poorer description of ores at a profit. Many deposits of ore of extraordinary richness have been discovered in the Comstock vein, and the ores from these it has been generally found most profitable either to ship to England, or to work by the barrel process. Amongst such ores may be instanced a lot of 80 tons, shipped from the California claim, which yielded on an average $2,200 per ton. But the main deposits vary in assay from $35 to $70 per ton, and it is the treatment of these ores which furnishes the largest proportion of the silver obtained from the district. The silver ores of Nevada are worked but to a limited extent in reduction works belonging to the mines themselves, but more com- monly on what is termed “custom work” at a fixed price per ton of ore of 2,000 lbs. The price charged varies according to whether or not a percentage amount of the assay value of the ore be guaranteed. If the ore be worked without guarantee, it is the interest of the mill- owner to pass as large a quantity as possible through the mill, con- AMALGAMATION.—PAN PROCESS. 391 sistently with the maintenance of a respectable character for the quality of the work done, since at any time when the supply of ore from the mines may slacken, an opportunity arises for working over the tailings, which always remain the property of the mill. As at the first working of the mines the mill power was insufficient for working the ore as rapidly as it was raised, its produce was only roughly estimated, and consequently not unfrequently overvalued, but a more satisfactory method is now generally adopted in the district. As soon as the ore is brought out of -the mine it is deposited on the pile or floors in parcels of from two to three hundred tons, every tenth waggon-load being reserved for dry stamping, so as to allow of careful sampling. The crushed ore is forwarded with the parcel to which it belongs, a small charge being made for crushing. The small sample retained by the mine is assayed, and from it the gross assay value of the whole parcel is determined, and the charges by the mine against the mill made accordingly. Ores at the mines are usually assorted into three classes, The first consists of those whose assay value is over $90 per ton of 2,000 lbs. As these contain but a small proportion of free silver, or silver in the metallic state, but have in their composition a considerable amount of sulphur, in combination with “rebellious metals,” such as antimony, zine, lead, copper, and iron, they are reserved for treatment by cal- cination and subsequent reduction in barrels by the Freiberg process. The second class consists of ores of the assay value of from $40 to $90 per ton. The third class ranges from $20 to $40 per ton ; the second and third classes are worked by the pan process. These ores usually contain, in value, about one-third gold to two-thirds silver. Ores of the first class are crushed by dry stamping, those of the second and third are crushed wet. The ores are prepared for stamping by being crushed into fragments of about a pound in weight by Blake's crushers. Stanvping.—For wet crushing, stamps are used of from seven to nine hundred pounds per head, including the stem, and are driven at the rate of seventy blows per minute. They are fed by an attendant whose duty it is to regulate the supply of ore, water, and quicksilver, when that metal is used in the battery for amalgamating the free gold present. Amalgamation in the battery requires careful attention, principally to avoid the too rapid addition of quicksilver, which should be supplied in very small quantities only. To amalgamate the free gold in a battery, the quantity of quick- 392 SILVER. silver to be used is about one ounce weight to each ounce of gold present ; this is sufficient to collect the gold and form a dry amalgam. If, therefore, a mill will stamp 24 tons of ore in 24 hours, and the ore contains an ounce of gold per ton, it will be necessary to put into the battery an ounce of quicksilver every hour. When, in addition to gold, the rock under treatment contains metallic silver, the amount of mercury added must be proportionately increased. More than 80 per cent. of the assay value of the gold in the ore may, by careful manipulation, be thus obtained. The gold amalgam accumulates in the corners and crevices of the battery box, between the dies, on the breast of the mortar, over which the crushed ore is washed into the settling cisterns, and is even found in considerable quantities adhering to the shoulders of the stamp shoes. The amalgam thus obtained is very hard and heavy, and is commonly so rich in gold, as to be worth as much as ten dollars per ounce. The crushed ore is taken off from the mortar by a supply of water, equal to the run of a three-quarter inch pipe to each set of five stamps, through screens in the back and front of the box. These screens are made of thin Russian iron perforated with holes punched by sewing-needles, with the points cut off, and set in dies as closely as consistent with the maintenance of sufficient strength to bear the necessary concussion, The needles employed are usually those known as Nos. 5 and 6, Settlers —The troughs by which the crushed ore is conveyed to the settlers are provided with gates or stops in order to allow of the suc- cessive filling and emptying of the different tanks. These are made of wood usually about ten feet in length by eight in width, and three feet in depth. Here the ore is allowed to settle, and the water is run from tank to tank, and not allowed finally to escape until it has become tolerably clear. As the water flowing from the settlers still contains much fine clayey matter, it is led off into one of a series of tanks which are successively filled, and after being again allowed to settle, the clear water is run off. This setthng is much expedited by the use of two or three ounces of alum to each thousand gallons of water contained in the tank. It must be added in solution to each cistern of foul water, as soon as it has become filled, and sufficient time must be allowed for settling before the clear water is discharged. When the cistern is sufficiently full of mud it is run off, and the tailings dried for further treatment. Ores of the assay value of $80 per ton produce tailings of the value of $100 per ton, and in ae 1 aaa AMALGAMATION.—PAN PROCESS. 393 such quantities as-to be equal to 20 per cent. of the total assay value of the ore. Of the amalgamating pans employed in the reduction works of Nevada, it may be said that their modifications are almost endless. Much ingenuity has been expended on many of them, but the best are those of Varney and Wheeler, and that of Hepburn and Peterson. These makers have, however, all obtained patent rights, and supply their various amalgamators to the different reduction establishments at a fixed price; which includes the necessary licence for using them. Common Pan.—There is, however, a more simple form of apparatus usually known as the common pan, with which results can, by careful working, be obtained almost as good as from those of the above makers. The common pan, Figs. 52 and 53, is a round wooden or cast iron Fia. 52. ZLLIPLIDL. ZZ Common Pan. (Vertical Section.) tub, 6 feet in diameter, and about 2 feet in depth, with a flat bottom. A false bottom of 14 inch iron is inserted into this, and a hollow pillar in the centre admits the passage of an upright shaft, which is generally worked by gearing, beneath the pan, capable of communi- cating to it from 15 to 20 revolutions per minute. To the wooden arms a are attached the blocks 0, also of wood, to which are fastened the iron shoes ¢, by means of the bolts d, passing up through the arms. Fach shoe has also an iron pin, about an inch in length, which fits into the wooden block and keeps the iron facing steadily in its place. 394 | SILVER. On the shaft f/, passing through the central pillar /’, is the yoke g, which, being fitted with a sliding key, can be raised by means of the screw / ; and the ends of the yoke itself being attached to the wooden cross arms, the mullers will be raised at the sametime. This arrange- ment for raising the mullers is not, however, very important, since they are usually allowed to grind with their full weight. Steam is introduced into the pulp by the pipe 2, the discharge being effected by means of the apertures J. The false bottom is made one inch less in Fre, 53; Common Pan. (Plan.) diameter than the bottom of the pan itself, and has an aperture in the centre an inch larger in diameter than the base of the pillar, in which the vertical shaft works. To fasten the bottom in its place, and prevent the mercury from finding its way under it, strips of cloth, about two inches in width, are lapped around the edge of the false bottom, as well as applied against the sides of the pan. A little iron cement is then poured in, and the bottom secured in its place by means of well-dried wooden wedges tightly driven between the two layers of cloth. These AMALGAMATION.—PAN PROCESS. 395 wedges, which are driven quite close to each other, must be somewhat shorter than the thickness of the false bottom; thus leaving a space above them which is subsequently covered with a paste of iron cement, that is allowed to set before using the apparatus. About one horse-power is required to work this pan, which will amalgamate from one and a half to two tons of ore in the course of 24 hours. Varney’s Pan.—A drawing of this apparatus ‘to scale is given Plate VII. : fig. 1 is a Vertical Section of this amalgamator ; fig. 2, a Plan of the parts beneath pan; fig. 3, Elevation of the amalgamator complete; fig. 4, View of interior of amalgamator ; fig. 9, View of one-half the lower dies with wood in slots ; fig. 6, View of under side of one-half of muller with shoes attached ; figs. 7 and 8, Stand for gear on vertical shaft; and fig. 9, Pillow-block for the driving shaft. The body of the amalgamator consists of a pan or tub A, figs. 1 and 8 with covers, through which is an opening for the introduction of the pulp to be ground and amalgamated. The pan is supported on suitable framework, shown in fig. 2. From the centre of the pan and extending from its bottom, to which it is cast, some distance above the cover stands the vertical tube D, through the interior of which is a hole passing vertically through the pan, in order that the shaft C may work through it. On the bottom of the pan, and secured to it by bolts ¢, is fixed the lower muller a, consisting of a circular iron plate having a round hole d in its centre, considerably larger than the base of the tube D. This die may, if desired, be made in sections. That portion of the hole through the muller not occupied by the tube D, is so filled with wood as to present a plain surface from the tube-to the circumference of the muller. The diameter of this muller is somewhat less than that of the interior of the pan, by which means a space a’ is left to be filled with quicksilver. Above the lower muller is the upper one B, of like general form and size, having twelve shoes ¢, the form and relative positions of which will be understood by sup- posing a plate of the diameter and thickness of the lower muller attached to the under side of the upper one, and sawn into twelve equal parts on lines drawn from the circumference of the plate to the outside of the tube D. The saw must also be supposed to be held inclined at an angle of about forty-five degrees, thus forming radial grooves from the inner to the outer opening. Each shoe is fastened to the muller by a bolt, or a wrought iron rivet, cast into the shoe and riveted into a counter-sink on the upper side of the muller, as shown at /, fig. 1; the bosses and recesses j, keep 396 SILVER. the die in its place. In the lower muller are radial slots, similar to those in the upper one. These slots may be either inclined laterally or be made vertical. The slots in the lower muller are filled with wood, so as to grind on its end, in order that it may be kept slightly worn, in advance of the wear of the die; thus furnishing a cavity for the admission of pulp between the surfaces, by which the grinding capacity of the machine is greatly increased. Over and around the tube D, but not in contact with it, is placed the larger tube E, exactly perpendicular to the lower face of the upper muller, and having around its lower extremity the flange v, upon which rests the ring #, which is cast with, and forms a part of, the upper muller. This is connected with the muller by means of six curved arms 2, two pairs of which are much nearer together than the others, and the space between them is filled by a projection from the periphery of the flange v, for the purpose of carrying with it the upper muller when the flange makes a revolution. To the shaft c is fastened the large tube E by the feather %, and set screws / in the hub G. The shaft c passes through a Babbet metal bearing at m, and through the boss F of the driving wheel, in which is a feather sliding vertically in the shaft. The shaft is stepped, by the ordinary method, into the vertical sliding box H, which is itself held in the laterally adjustable box 0. The step box rests upon an iron bar, one end of which is supported by a screw bolt w, fig. 4, and the other is held by a bolt and hand wheel 2, figs. 3 and 4, by which it can be either raised or lowered; — raising or lowering the upper muller at the same time. Within the body of the pan are suspended three curved plates 7, figs. 1 and 4, extending from near the surface of the upper muller upwards, and stretching in length from the inner side of the pan around to a point near the outside of the large boss, opposite that from which they started. The lower edges of the curved plates are bent inwards, as shown at s, fig. 4, forming flanges. The inner ends of the curved plates are secured rigidly to the ring g, of sufficient diameter to surround and clear the tube E; the whole being suspended by a rod attached to each plate, passing through the cover and hand wheels J, by which it may be adjusted. The outer ends of the curved plates slide vertically in grooves in the projections ¢, cast upon the inner side of the pan. The operation of this apparatus is as follows: The space a’ about the periphery of the lower muller is filled with quicksilver, and the pan yy Se . Bast in: é — =r ibs Ai rarKae, Lae tle SHoll orTe Castle J 7 43 Ca & Om Ne bery pe as SO / We Va f 2 | = zu x A ae: pe = = = : 4 LEO 7 . 1 = VL: Lf ed bi N Fig. 9. heed hole REFERENCE. A. Pan or tub B. Cover. C. Vertical. shatt D. Central tube. E. Exterior tubes F. Boss of drwing wheel. G. Hub of outer the. A, Sluding bearing. J. Hand wheels. O. Adjustable box. V. Klange of outer tube. a. Lower mudtler. a. Space tor mercury. 6. Upper mictler: ° c. Shoes of d. Hele in centre of lewer nucller: e. Bolts SeCurUrg ' « fF. Bolts securing shoe to upper , hk. Ring om upper muller t. Carved arms of, hk. Shing hey. J Lugs toheep shoes in place tl. Set-screws. m. Babits Metal bearing. gq. Ring supporting curved plates. Curved plates. Th 8 Flanges of curved plates (Brackets supporting wo bulerian of lever: ax Hand wheel for litting muller ; Newbery & Aleccande; [uh 43, Castle S*Holborn Ea FN Spon 48 Charing Gross.Lomdoi , AMALGAMATION.—PAN PROCESS. 397 nearly filled with pulp, of the proper consistency to flow easily; the shaft C is now made to revolve at a proper speed, from sixty to eighty revolutions per minute, by which the upper muller is rotated. The pulp between the mullers, by means of the centrifugal force developed, is made to pass out through the radial channels between the dies, as well as between the grinding surfaces of the upper and lower mullers ; also into and over the quicksilver, thereby causing amalgamation. The outward motion of the pulp has the effect of keeping the quicksilver entirely away from the grinding surface, thereby obviating what has often proved a very serious difficulty—viz. the grinding of the mercury. The rotation of the upper muller causes the pulp in the pan to revolve with it. This current is met by the cuneiform projections and curved plates, and thereby turned towards the central opening in the upper muller. The radial slots between the shoes, running from the central opening to the outward one, allow currents of considerable size to pass with great velocity ; and the pulp filling these slots, being continually thrown outwardly, tends to produce a vacuum. By this the pulp in the body of the pan is set in motion, causing a rapid and abundant flow downwards at the centre, and upwards along the inner surface of the pan. The pulp is thus made to circulate, until complete pulverisation of the quartz and amalgamation of the metals have taken place. Wheeler's Pan.—This apparatus, which in size and certain other respects closely resembles that of Mr. Varney, is represented Fig. 54; A being the pan, with the dies a, in their several places; whilst B represents the rotating muller, fitted with its shoes 6, removed from the pan, and turned bottom upwards. The upper muller is, like that of the pan last described, driven by means of a hollow cone, which passes over the central pillar, and is connected with the vertical shaft by means of a sliding key. As in the case of the other pans, the distance between the mullers is regulated by a screw, fitted with a hand wheel. The shoes 6 are secured to the upper muller, either by bolts and nuts, or more fre- quently by projections passing through inclined oblong holes in the rotating plate, to which they are firmly secured by means of wooden wedges. The dies a are laid on the bottom of the pan, and kept in their places by the ring ¢ in the centre, and on the sides by the inclined ledges d, under which their ends are wedged. The dies, like the shoes, are one inch thick, and bevelled on the edges in the same 398 | ; SILVER. direction ; so that, when put together, grooves are formed between them, as shown in the drawing. On the upper side of the outer edge of the muller are inclined ledges, which, in connexion with those, d, cast on the pan, create an upward current in the pulp ; whilst euide plates, somewhat similar to those of the Varney Pan, which slide into grooves at e, convey it towards the centre. This pan stands on a cast iron framing, and is driven by mitre wheels from beneath. Fie, 54. | ——F WHuEELER’s Pan. From the dies and bottom not being cast perfectly true, the grinding surfaces are often, at first, a little uneven, and consequently the grinding planes should not at once be brought into too close contact, _ The runner of these pans requires to be lifted at least once a week, for the purpose of removing the amalgam which accumulates around the central pillar, and thus prevents the pulp from passing freely be- tween the grinding surfaces. This pan, like that previously described, is generally made four feet in diameter at bottom, and requires from two and a half to three horse-power to work it efficiently. It usually makes about sixty revolutions per minute. AMALGAMATION.—PAN PROCESS. 399 Hepburn and Peterson's Pan.—This pan differs mainly from the foregoing, as will be seen by the annexed illustration, Fig. 55, in the Fig. 55. Ih Wy Ay tay ‘ ru Ny um SSS Mati HEPBURN AND PETERSON’s PAN. shape of the bottom, which is inclined towards the centre, or shaped like an inverted cone. The shoes are bolted to this cone, and the cor- responding dies fastened to the bottom. When the pulp is thrown into this apparatus, and the mullers set in motion, that portion of it which finds its way between the grinding surfaces is thrown towards the circumference, from whence it again descends by gravitation to the centre, and passes between the mullers. A constant and active circulation is thus established without the aid of curves or wings ; which have sometimes been found an impediment in starting similar machines, after the sand has become packed from stopping. Under all ordinary circumstances, however, this or any of the other well- constructed amalgamating pans may be readily started, without either 400 SILVER. - removing or thinning down the pulp, by simply elevating the muller, by means of the screw and movable nut with which they are now generally provided. The charge for this pan is about 1,400 Ibs. and the time required for working 1t is from two to four hours, in accordance with the fineness of its state of division and other characteristics. When the ore has been sufficiently reduced and amalgamated, the pulp is, after dilution with water, discharged into another pan, called a separator, and the amalgamating pan imme- diately re-charged, without stopping the machine. After the pulp has been run off into the separator, it is further thinned down with water to such a consistency as will allow the mercury and amalgam . to settle, whilst it still retains sufficient plasticity to hold. the coarser particles of ore im suspension in water. The condition of the pulp is readily ascertained by placing the hand in it during the process of separation. If it be in a proper state of dilution, the mercury and amalgam will gradually precipitate, and at the same time no per- ceptible difference will be felt in the consistency of the pulp situated near the bottom and that at the top of the vessel. "When, however, too large a proportion of water has been added, the coarser particles will be felt to distinctly separate from the slime, and strike against the hand when placed near the bottom of the separator. In working these, or other similar machines, the charges are generally so regu- lated that only one charge, from the two pans, working in conjunc- tion with a separator, may be ready to operate on at a time; thus taking, in each case, one-halt the time for effecting the separation that is consumed in reducing and amalgamating. Some amalgamators, however, prefer to occupy the same length of time in effecting the separation that is required for amalgamation; and in this case the separators require to be of larger dimensions, or to be more numerous, since both pans are run off together. The Hepburn and Peterson Pan is much employed in the reduc- tion establishments of the Pacific Coast, and, in addition. to being an excellent amalgamator, is also a good ovinder; but it has the dis- advantage of requiring the expenditure of from four to five horse- power for its efficient working. The charge of the Wheeler Pan is not only less than that of the Hepburn and Peterson Pan, but its grinding power is also less considerable. This pan usually makes between fifty and sixty revolutions per minute. . Separators.—These differ more or less in their details, but generally consist of a large wooden tub, having a considerably greater diameter AMALGAMATION.—PAN PROCESS. 401 than the pans, and provided with a cast iron bottom. Arms and mullers are attached to a shaft working through the centre of this bottom, as explained when describing the construction of the common pan. In this case, however, the mullers are sometimes made of mere blocks of hard wood, the object being simply the agitation of the pulp for the purpose of concentrating at the bottom the quicksilver and amalgam run off from the pans. The mullers in the separator are only allowed to make from ten to twelve revolutions per minute. Working in Pans.—The reduction process simply consists in treat- ing the pulverised ore in cast iron pans in such a way as to cause the amalgamation of the gold and silver it contains. The same principles are to a great extent involved in this process as in the Mexican patio; but, by intelligent modifications of the treatment, as much is accomplished by the former in a few hours as can be effected by the latter in as many weeks. Although the improvement on the old Mexican process already made has been very great, much yet remains to be accomplished. In order to the most complete and perfect separation of the metallic from the earthy constituents of the ores, it is first necessary that they should be reduced to an impalpable powder by grinding. This is but imperfectly done by the stamping mill, and much is left to be accomplished by the pans. The friction of the pan should not, however, be more than sufficient to insure the perfect mixture of the ingredients which it contains, in such a way as to promote a rapid series of chemical changes, resulting in the decomposition of the constituents of the ore, and the combination of the precious metals with mercury, at the least possible cost of power and material. With this view, from twelve hundred and fifty to fifteen hundred pounds of ore, from the tanks of the stamping mill, are put into the Varney or Wheeier Pan, and the grinding muller gradually lowered until the whole mass has become reduced to an impalpable powder. This is usually accomplished in about an hour. Loose steam is then turned on until the temperature has been raised to 200° Fahr.; but care is at the same time taken not to render the pulp too liquid by the accumulation of condensed water. The muller having been slightly raised, to prevent too great an amount of friction between it and the dies, quicksilver is gradually added in the form of a fine shower, by pressing it slowly through a canvas bag. The quantity of quicksilver used varies, according to the richness of the ores, to from ten to fifteen per cent. of the weight of mineral operated on. Amalgamation is DD 402 SILVER. further promoted by the addition to the pulp, immediately after introducing the quicksilver, of sulphate of copper and a small quan- tity of sulphuric acid. For second class ores, two pounds of sulphate of copper, in solution with an equal quantity of sulphuric acid, and three pounds of salt, may be advantageously employed.* An endless variety of substances has been used for this purpose, since at one period every amalgamator prescribed some new specific for avoiding imperfect amalgamation ; but those above enumerated have alone maintained a permanent character for efficiency.t Much, however, yet remains to be accom- plished by a more careful study of the modifications rendered neces- sary by the varying constitution of the ores operated on. The run- ning of the pan is continued for three hours and a half, the heat being maintained at from 180° to 200° Fahr. At the expiration of this time, water is run into the pulp to render it sufficiently liquid to flow off, through a valve in the bottom of the pan, into the agitator or sepa- rator. The pan is then roughly washed down, and, with as little delay as possible, recharged with ore,as before. A Varney Pan four feet in diameter is capable of working six charges in twenty-four hours, or from 7,500 to 9,000 Ibs. of ore. Once or twice a week, or at the finishing of any particular parcel of ore, the muiler is taken out, the shoes and dies removed, and all the amalgam adhering to the working parts, or deposited in the crevices, carefully scraped off. A notable accession to the product is thus obtained, especially as, at the same time, the mortar bed of the stamps is likewise cleaned out. | In the separator the pulp is mixed with a large quantity of water, and a regular steady supply kept up, so as to carry off the lighter particles of earthy matter, at first from holes in the upper part of the pan ; but as the separation proceeds, the discharging point is eradually lowered, until eventually nothing but the heavier pyrites and liquid amalgam is left. The amalgam is drawn off from the bottom, and the pyrites then scooped out, and, after being further washed in another * Dr. Oxland, who has had considerable experience in the treatment of silver ores by the pan process, informs us that he has obtained as good results with sulphate of copper alone, as with the addition of salt and sulphuric acid. + It is scarcely necessary to notice the various absurd ingredients which have occasionally been employed in Nevada with a view of facilitating amalgamation, such, for instance, as tobacco juice, decoction of sage bush, and of oak bark ; since any success which may have attended their use must manifestly be attributed, rather to a fortuitous combination of circumstances, than to any direct action of the materials themselves. AMALGAMATION.—PAN PROCESS, 403 separating pan, to remove the last traces of amalgam, it is reserved for final treatment by calcinaticn and reduction in barrels. The amalgam is now carefully washed in clean water, dried with flannel, and finally _ removed to the amalgam room, where it is strained through thick conical bags of canvas, twelve inches in diameter at the larger end and two feet in length.* After the bags have drained for some time, they are beaten with around stick to cause a further quantity of the mercury to run off. The hard dry amalgam is finally removed from the bags, and weighed into store. The mercury run off from the bags is technically known as “ charged quicksilver,” and, after being mixed with retorted mercury, is returned to the pan room for further use. Charged quick- silver is preferred to the pure metal, as with it amalgamation is found to proceed more rapidly. etorting—The amalgam is finally handed over to the assay office belonging to the mill, and the separation of mercury is effected by exposing the amalgam to a red heat in a cylindrical cast iron retort, about twelve inches in diameter and three feet long, mounted on* an arch of firebrick, and placed within another arch, from the crown of which the smoke is carried off to the chimney. The retort is fitted with a stout cover, carefully adjusted like the stopper of a coal-gas retort. From the upper part of the end, a two-inch iron pipe carries off the volatile matters. This is so fitted to the downcast pipe, four feet in length, that, by T-pieces and stoppers, every facility is afforded for cleaning out the pipes. The downcast pipe is so fitted within another pipe, 34 to 4 inches in diameter, as to constitute a Liebie’s condenser, into the bottom of which cold water is supplied; the heated water flowing off from the top. The downcast pipe opens into a small bottomless chamber, immersed sufficiently low in a tank of water to keep it air-tight, but in such a manner as to prevent accidents from the absorption of water into the heated retort. This retort is provided with several cast iron semicircular trays, which slide easily in and out; these are divided into two parts by a transverse partition. Before the weighed charge of amalgam is put into the tray, it is coated with milk of lime, or a thin wash of clay, * The washing of the amalgam is generally effected in a vessel called a cleaning up pan, provided with four arms furnished with shoes like those represented, Figs. 52 and 53. In some cases, however, the matters escaping from the separators are now run off over blankets on which a certain proportion of the undecomposed sulphides is caught, and this is subsequently re-treated either by barrel amalgamation or otherwise. DipeZ 40-4 SILVER, and not unfrequently a sheet of paper is also placed over the bottom. By these precautions the retorted amalga:: 1s prevented from adhering to the iron, and much trouble avoided. The charge having been placed in the retort, the cover is carefully luted with a mixture of clay and wood ashes, made up into a thin paste. The fire is then lighted, and the heat slowly and steadily raised, until the retort 1s of a bright red colour, and is so maintained until the mercury ceases to distil over, The retort is now allowed to cool gradually down, and when cold the retorted silver is withdrawn and weighed, as is also the mereury obtained, as a precaution against any possible loss of quicksilver from hidden leaks in the retort. The retorted amalgam. is broken up, melted in plumbago crucibles, and cast into bars or ingots of “bullion” of from one thousand to fifteen hundred ounces | each. These are assayed and valued, the value being marked on the bars, which are then ready for the market, The quality or “fineness” is marked in thousandths, thus—gold 24, silver 841, making together 865 thousandths; leaving 135 parts in a thousand, which principally consist of copper; but no notice is taken of this, as it is of no money value in the sale of the bar, The retort employed at the mills near Virginia for the distillation of silver amalgam is represented, Figs. 56 and 57, of which the first is partially in section, and the second is a longitudinal section. The ash-pit A is beneath the fireplace B, which communicates, by means of flues a, with a chamber 0, enclosing the cast iron retort ¢, from which the products of combustion are conveyed by the flues 1, 2, 3, through the arched cavity ¢, to the chimney @. By dampers covering these flues the draught may be controlled so as to heat the retort according to the requirements of the case. The pipe D carries the vaporised mercury to the vertical pipe E, in which it is condensed, by the action of a stream of cold water passing upward from the bottom through the Liebig’s condenser Fr. The con- densed mercury collects in the reservoir G, from which it is drawn off into bottles through a bent tube at the bottom. Any vapours escaping from the retort door are conveyed into the flues by the hood e, of sheet iron, The arrangement of the cover of the retort is shown at g, and a portion of the semi-cylindrical tray, used for charging the retort, at h; the position of the iron plates and braces for binding the brick- work is represented by the letters /- The best results obtained by the pan process rarely amount to 75 per cent. of the assay value of the ore; the average will scarcely AMALGAMATION.,—PAN PROCESS. exceed 65 per cent. The barrel process, being more expensive, cannet be employed in Nevada except on ores of the first class. The tailings from the pan process, after having been exposed to the action of the at- mosphere for a few months, may sometimes be again advantageously worked over, thus increasing the total produce to about 85 per cent. ; but it is only under favourable circumstances that this can be done. Fig. 56. RETORT. (Front Elevation.) The cost of working from $45 to $50 ores by the pan process is, in those portions of the State of Nevada in which water-power can be obtained, nearly as follows :— Stamping wet, through No. 6 screens . . . . $1°50 per ton. Milling, including loss of mercury, &c.. . . . 500, ,, Total cost, including wear and tear . . $6°50 ,, _,, The loss of mercury amounts to from 14 to 14 lb. for each ton of ore containing silver to the amount of from $35 to $50 per ton. 406 SILVER. Arrangement of Reduction Works—The usual arrangement of crushing and amalgamation works for the treatment of silver ores by the pan process, where water-power is available, will be understood by reference to Plate VIIT., which represents a transverse sectional elevation of an establishment in Nevada, in which Wheeler’s Pans are employed. The water-wheel A communicates its motion, by means of toothed segments around its periphery, to a pinion shaft on which is ae ale is RETORT. (Longitudinal Section.) the drum B, which, in its turn, transmits the power, by means of broad composition belts, to the whole of the machinery employed in the establishment. The dimensions of the second pulley c, and that on the shaft D, are so calculated as to cause each stamper to be raised from 70 to 80 times per minute. The stops d are employed for sup- porting the stampers when not in action, and are for that purpose AMALGAMATION, PAN PROCESS. 407 slipped under the bosses or tappets on the iron stems, when raised to the full extent of their course by the cams keyed on the shaft set in motion by the pulley p. The tightening pulleys E are for the pur- pose of keeping the different straps in a proper state of tension. The stampers F discharge the pulverised ore, through the grates or screens f, into the spouts g, which conduct it to the receiving tanks G,@’. The hand wheel u is employed for opening and closing the valve h, by which the supply of water to the wheel can be either regulated or cut off. From the amalgamating pan I, the s/wms are run off, through the spouts 7, into the separator kK, which is provided with the over- flow k. The cleaning up pan, L, with the other pans and separators, receives its motion from belts driven by pulleys on the shaft 0. The pipe M affords the necessary supply of water, whilst N is the steam pipe by which the heating of the pulp is effected. In the drawing, the pan is represented as having a false bottom, for the purpose of heating the pulp by the introduction of steam, but in practice it is generally now found more convenient to blow loose steam directly into the pulp. The hand wheel P is for the purpose of regulating the tightening pulley =. This mill has twenty stampers, twelve Wheeler Pans, six separators, and two cleaning up pans. AMALGAMATION OF ROASTED ORES IN PAns.—In some of the mining districts of Nevada, and particularly in the neighbourhood of Austin, where the ores consist of various compound sulphides of silver, con- taining a considerable amount of antimony, the ordinary pan process, as practised in Virginia, cannot be advantageously employed. The ores from this part of the State consequently require roasting before being subjected to amalgamation, and then, when worked in the pans, afford better results than those obtained from the ores of the Com- stock vein treated in their raw state. Each battery of five stampers will crush (dry) four tons of ore daily, through a wire gauze screen of 40 holes per linear inch. One thousand pounds of this crushed ore is roasted with 8 per cent. of common salt ; the time occupied in the furnace by each charge being, on an average, six hours. Varney’s Pans are most commonly employed, and are charged with - from 800 to 1,000 Ibs. of roasted ore, which occupies five hours in working. A mill of ten stampers, with all the necessary furnaces, pans, and appliances, will treat eight tons of ore in the course of twenty-four 408 SILVER. ° hours, with a total consumption of about ten cords of wood. The following figures, relative to the treatment of roasted silver ores by pan amalgamation, give the results of an experiment made at Virginia city on ores from the Comstock vein, but it is stated that the loss of silver in the neighbourhood of Austin, where the ores contain little or no gold, seldom exceeds 7 per cent. of the assay value. Results of an Experiment showing Loss of Metal by Amalgamation of Roasted Ore in Pans, Value of ore in gold $112°85, in silver $180°37 . . . $293°22 » Bullion 9740, ud: 16299 . . . 260°42 eS SgOR 13°60 per cent. 9°06 per cent. 11°18 per cent. Loss of quicksilver greater than in barrels. 20 Feet 715 ii =f LU SILVER Eee Veaet ON OF REDUCTION WORKS, AJ BURN STATE of NEVADA. ie ANS WW BE SSS Zz” i= ANY My YW | || AWA K \ ( La Se Eis EN. Spon,48, Charing: Cross.London. ANNE Pee || Siete, Getenieheeeteteeeeesenn ane: a aaa OO il aI NSE NEY SP mhaSa we CHAPTER XIX. TREATMENT OF ARGENTIFEROUS ORES AND PRODUCTS BY SOLUTION AND PRECIPITATION. AUGUSTIN’S PROCESS—ROASTING WITH SALT—LIXIVIATION AND PRECIPITATION— ZIERVOGEL’S PROCESS—ROASTING—SOLUTION OF SULPHATE OF SILVER—PRECI- PITATION OF SILVER BY COPPER — VON PATERA’S PROCESS — ROASTING WITH COMMON SALT—SOLUTION OF CHLORIDE OF SILVER IN HYPOSULPHITE OF SODA —PRECIPITATION BY SULPHIDE OF SODIUM — TREATMENT OF SULPHIDE OF SILVER. THE different processes by which silver is obtained by the wet way from the various ores and metallurgical products containing that metal are all of recent invention, and belong to the latest period in the history of metallurgy. These methods have now, in many cases, supplanted the older processes of liquation and amalgamation, and may be often advantageously adopted for the treatment of argen- tiferous compounds ; particularly when the amount of lead present is small, and the proportion of copper large. They all possess the advantage, over amalgamation, of entailing no loss of mercury, and in the promptness and completeness with which the metal may be extracted. They are also, from requiring less time and fuel, and in being attended with a smaller loss of the various metals contained in the substance under treatment, less expensive than fusion with lead ores. The several wet processes are likewise more expeditious, and require a smaller amount of fuel than the old method of liquation ; besides which, they effect a much more complete separation of the copper and silver. AvuaGustin’s Proctss.—This method of treating argentiferous com- pounds was first introduced in 1849 by an officer of the Mansfeld Copper Works, at the Gottesbelohnung Works, near Eisleben, im Prussian Saxony, where, after being retained for a short time, it was superseded by the cheaper and still more simple process of Ziervogel. Augustin’s method of extracting silver from its ores 1s dependent on the following circumstances :— +10 SILVER. Ist. That the silver contained in ores of that metal may be converted into chloride of silver by roasting them with a proper admixture of common salt. 2nd. That a solution of common salt will dissolve chloride of silver in quantities depending on its temperature and state of concen- tration.* srd. That the silver contained in an argentiferous solution of chloride of sodium is precipitated in the metallic state by copper. At Freiberg this system is employed for the extraction of silver from a regulus or copper matt, containing about 70 per cent. of copper and 0:0042 of silver, besides a certain amount of iron, anti- mony, and arsenic, with other impurities. In order that this matt may be properly roasted, it is first ground to a very fine powder and bolted through sieves of wire gauze. Roasting.—The furnace employed for this operation is He the ordi- nary reverberatory description, the fuel employed being pit coal, and the weight of the charge treated four hundred pounds. One work- man attends to each furnace, and the fire, which at first is kept low, is gradually raised, care being at the same time taken to keep the powdered matt constantly stirred, in order to prevent caking, and that every portion may be equally exposed to the full temperature of the hearth. At the termination of eight hours the operation begins to approach completion ; the bright glow, indicative of the presence of sulphur, disappears, and sulphurous acid is no longer evolved. The charge is now withdrawn from the furnace, and, after being allowed to cool, is ground between burr stones, passed through a fine bolt, and subjected to chlorination. Roasting with Salt.-The roasted matt, in which, at this stage of the operation, the copper and iron chiefly exist in the state of oxides, whilst the silver has either been converted into a sulphate or reduced to the metallic state, is now roasted in charges of three hundred pounds weight, in furnaces similar to those employed for the first. operation. After being for a short time exposed to a low temperature, common salt, to the amount of 5 per cent. of the weight of the charge, is introduced, and the roasting continued, with the usual amount of “ At a temperature of 32° Fahr. the amount of chloride of silver dissolved by a solution of common salt is almost inappreciable. At 50° Fahr. a solution of salt takes up chloride of silver amounting to 0°0017 of the weight of chloride of sodium present, at 64° its dissolving capacity has increased to 0:0024, and about 212° to 0°0068, of the amount of salt in the brine. ae ra ii Raa tied - * SoD, Se ee ae ee Lee ee a eee ee AUGUSTIN’S PROCESS. 4141 stirring, for about three hours. By this means the decomposition of the chloride of sodium is effected through the agency of the sul- phuric acid of the metallic sulphates ; and, by the combination of chlorine with the silver present, nearly the whole of that metal be- comes converted into chloride. The charge is now withdrawn from the furnace, and is ready for the process of lixiviation. _ Lizxiviation and Precipitation.—The lixiviation of the matts thus prepared takes place in an upper story of the establishment, and is conducted in a series of tubs ranged in a line along one of its walls. The construction and form of these vessels will be understood by reference to Fig. 58, which represents one of the lixiviating tubs with the portion nearest the spectator removed. Upon the bottom a is LIXIVIATING TuB. first laid a wooden cross 6, on which rests the perforated false bottom c,on the top of which is again arranged a layer of straw d; above this is placed a filter of linen cloth, made tight against the sides of the tub by means of a hoop, and on this is deposited the roasted matt to be lixiviated; the filtered liquor being drawn off by means of the tap d’. These tubs are three feet nine inches in height, two feet eight inches in diameter at top, and two feet four inches at bottom. Hight of them are charged at the same time, each with eight hun- dred pounds of the prepared matt; and a stream of hot brine-is directed, through a perforated cover, into each, by means of suitable pipes arranged for that purpose. The chloride of silver being thus 412? SILVER, dissolved in the hot solution of chloride of sodium, is carried by it through the filter, and flowing off by the taps d', is conducted through a wooden gutter to a covered tank, in which the particles of ground matt, carried off in suspension, are allowed to settle. The liquors from this settling tank are now conveyed to a series of three tubs, which, like those already described, are all furnished with false bottoms and filters ; being also so placed one above the other that the liquor escaping from the tap of the first will flow into the second, and from thence into the third and last vat. In the bottom of-the two upper tubs is placed a layer of cement copper from six to seven inches in thickness, whilst on the filter of the last is laid a quantity of scrap iron, On admitting the saline liquor into the first of these tubs, a large proportion of the silver which it contains is precipitated in the metallic form at the expense of the copper, which, by combining with the chlorine of the chloride of silver, is itself in turn converted into chloride, The liquors escaping from this tub are received into the second of the series, also provided with a thick layer of cement copper, by which the last traces of silver are precipitated. The liquid, which has been thus freed from silver, but has now become highly cupreous, falls directly into the lowest tub, containing scrap iron, by which the copper is deposited in a form suitable for the precipitation of silver in the upper tubs during succeeding operations. : The brine flowing from the last tub, and deprived both of its silver and copper, is now pumped into a proper receiver, and, after being boiled, may be again used for lixiviation. In this way the hot brine is passed through the lixiviating tubs until a plate of bright copper does not become coated with silver when held for some time in the liquors escaping from them. The residual matters remaining in the tubs, and which chiefly consist of oxide of copper, are then removed to give place to fresh charges, but before being treated for copper are assayed, in order to ascertain the amount of silver which they still retain. Should they be found to contain more than a quantity corre- sponding to 0:0003 of the weight of matt operated on, they are again roasted and lixiviated; but if, on the other hand, the proportion of silver be less than that stated, they are at once fused for copper. The cement silver, in the form of a crystalline powder, is about once a week removed from the tubs in which it has been precipitated ; and after being treated with dilute hydrochloric acid, for the purpose of removing any traces of copper, is thoroughly washed with clean a et Se, “ ZIERVOGEL’S PROUESS, 413 water. When sufficiently washed, the metallic sponge is pressed into balls, thoroughly dried, and taken to the Saxon mint, where it is purified and fused into bars. This process is at present only employed for the extraction of silver from matts in which that metal has, in conjunction with copper, become concentrated by repeated roastings and fusions. It may, however, under certain conditions, be found directly applicable to some of the various ores of silver, ZIERVOGEL’S Process.—Shortly after the adoption of Augustin’s process at the works belonging to the Mansfeld Company, the cheaper and still more simple method of converting the silver into sulphate, and subsequently dissolving it out by hot water, was introduced by Hiittenmeister Ziervogel, and since the year 1857 the whole of the argentiferous matts worked in the establishment have been treated according to this plan. The etticiency of the method of Ziervogel depends on the circum- stance, that when a finely-powdered matt, consisting of the sulphides of copper and iron containing a certain proportion of silver, is, with proper precautions, roasted in a reverberatory furnace, the iron and copper first pass into the state of sulphates, which are afterwards transformed into oxides: The sulphide of silver subsequently under- goes a similar transformation, and, if the roasting were continued, would ultimately be reduced to the metallic state. If, however, the operation be arrested at the proper stage, the copper and iron will have become transformed into oxides, whilst nearly the whole of the silver exists as a soluble sulphate readily removed by water; which thus affords a means of separating that metal from the other con- stituents of the charge, which are, for the most part, insoluble in that menstruum. From the argentiferous liquors thus obtained, the silver is afterwards precipitated by means similar to those employed in the method of Augustin; but when a solution of the sulphate is effected by the use of water, in place of dissolving the chloride by means of hot brine, nearly the whole of the silver originally present in the sulphides treated may be obtained in the metallic state. Roasting.—The matt, after being ground between a pair of mill- stones, four feet in diameter, made of the granite of the Hartz, is bolted through a circular sieve, of from 1,400 to 1,500 apertures to the square inch, and then carefully roasted in a reverberatory furnace, specially adapted to the purpose. This furnace, which is provided with two distinct hearths, placed 414 SILVER. one above the other, has an exterior length of nineteen feet, and a width of thirteen feet; its total height being about fifteen feet. The two hearths on which the roasting is conducted are each ten feet long by eight feet wide, and are built of good firebrick, of which all the parts of the apparatus subjected to a high temperature require to be con- structed. The fireplace is provided with a grate, from which the flame passes across a frebridge over the contents of the lower hearth, and, ascending a perpendicular flue, the heated gases are conducted, in a tortuous direction, through a number of channels over the arch of the upper chamber. In these flues are deposited the fine particles of matt mechanically carried over by the draught, and which are, from time to time, removed through suitable openings, for the purpose of being subjected to metallurgical treatment. From these horizontal flues the gases finally pass off into the chimney, whilst the upper hearth, being heated both from above and below, is in the condition of a muffle, through which none of the gases of the furnace are allowed to pass. This hearth is, therefore, well adapted for effecting the calcination of ores when they cannot be brought to a high temperature without danger of fusing. In the bottom of this hearth, passing through the arch of the lower one, is an aperture, closed by an iron plate, through which the charge can be raked into the lower bed of the furnace. When the roasting on the lower hearth is completed, the charge is raked through another opening, also covered by a plate, into an iron waggon, which is run into an arched tunnel beneath it, The ground matts from the mill are mixed with about 15 per cent. of the residues remaining in the tubs, after the process of lixiviation ; and from 500 to 600 Ibs. of the mixture is charged upon the upper hearth of the furnace, where it is exposed to a gradually increasing temperature, and kept constantly stirred during about seventy-five minutes. The portion of the charge most remote from the fire is now brought forward towards the bridge, and any lumps which may have been formed are carefully broken with an iron rod. The roasting is continued, as before, during another period of seventy-five minutes ; and at the expiration of two and a half hours from the first intro- duction of the charge, an addition is made of from 20 to 25 Ibs, of ground lignite, in a perfectly dry state. This is mixed with the pul- verised matt, by a stirring which occupies about ten minutes, when the plate is removed from the hole in the bottom of the muffle, and the whole of the contents of the upper chamber are raked through it, and spread evenly over the surface of the lower hearth. The heat applied iia ey . ZIERVOGEL’S PROCESS. 415 is, at first, moderate; but at the expiration of little more than an hour, during which time the charge has been constantly stirred, and the powdered lignite has become consumed, the temperature is con- siderably increased. | At the expiration of about ten hours from the time of first charging, the workman, who, particularly during the latter stages of the opera- tion, has kept the contents of the hearth carefully stirred, withdraws a sample, for the purpose of determining whether or not the roasting has become sufficiently advanced. This is done by taking, with a small iron ladle, a spoonful of the ore from different parts of the hearth, and, after placing it in a white earthenware saucer, dropping on it a little pure water, which is allowed to percolate slowly through the edges of the sample. In this way the water takes up any soluble salts which may be present in the roasted matt, and, from the colour assumed by the solution, a correct judgment can, after a little practice, be formed of the condition of the charge. The liquor which thus escapes from the sample of roasted mineral should present a slightly blue appearance, but be without any shade of green: the addition of a few grains of common salt should, moreover, produce a copious white precipitate of chloride of silver. When these conditions have been satisfactorily fulfilled by the sample taken, the operation is considered finished, and the charge withdrawn. Brush- wood, which makes a strong fire, with a long flame, is the only fuel employed in the roasting furnaces at the Mansfeld Works. - The success of this process for the extraction of silver manifestly depends on the degree of facility with which the operation of roasting may be controlled, so as to be enabled to seize the exact period at which the several metallic compounds are in the precise condition required. The sulphate of copper should be, as far as possible, con- verted into an oxide, whilst the whole of the silver ought to exist in the form of a soluble sulphate. Should the roasting be arrested before this point has been attained, a large amount of copper will be found to remain in a soluble state; whilst a portion of the silver still exists in the form of an insoluble sulphide. Tf, on the contrary, the roasting be carried too far, the sulphate of silver will have become reduced, leaving that metal in the metallic state; which, being totally insoluble in the hot water employed for lixiviation, will remain with the copper, and become commercially lost. Long practice and much observation are required on the part of the workmen employed in this process, and, with a view of increasing their efficiency, a scale of premiums has 416 SILVER. been instituted for any more than ordinary success in the work performed. This system of rewards has been particularly successful at Mansfeld ; for, although the process has not itself been in any way modified since its first introduction into the works, yet the skill of the workmen has, within the last few years, increased, in so marked a degree, that the results now obtained are much more satisfactory than those formerly yielded by this method of treatment. Lixiwiation and Precipitation—The roasted argentiferous matt is now taken to the lixiviation department, which consists of a large room, in which a number of vessels are arranged (as shown in the following woodcut, Fig. 59), and so placed that the liquors flowing from one are immediately received in the next which follows in the series. SY SSN SS asi we a Si i {Ui ZIBRVOGEL’S PRocEss. (Arrangement of Apparatus.) The powder to be operated on is divided into parcels, weighing A00 Ibs. each, which are placed in the vessels A, two feet six inches in diameter, and of about the same height, provided with filters and false bottoms ; twenty-two cubic feet of liquor from a previous operation, together with about three cubic feet of fresh water, both heated to a temperature of 160° Fahr., are run into each of the upper tubs through the pipes a,b. A little sulphuric acid is also employed for the purpose - ZIERVOGEL’S PROCESS. 417 of preventing the inconveniences which are found to accompany the presence of basic salts. This fluid, soon permeating the ore in the tubs A, takes up the sulphate of silver, and any other soluble salts present, which, passing through the filter, are carried in solution into the tank B, thirty feet in length, and eighteen inches square, divided into two parts. In this reservoir the liquors enter the first division, and, after allowing the matters held in suspension to settle, the solu- tion flows over the partition, and from thence through ten taps into as many tubs C: in the bottom of each of these are placed 10 Ibs. of cement copper and 250 lbs. of coarse copper bars, by which the larger proportion of the silver is precipitated in the metallic form. The fourth vessels D, of which there are five, also contain metallic copper, and in them are precipitated any traces of silver which may have escaped precipitation in the tubs c. From these last tubs the spent liquors flow off into the lead-lined cistern E; from which they are sub- sequently raised by steam pressure into another leaden cistern above the level of the first series of tubs A, heated to a temperature of 160° Fahr., and passed over a fresh charge of roasted matt, introduced into the series of dissolving vessels A. About two and a half hours are required to dissolve out the sul- phate of silver contained in each charge; and at the end of that time the residual contents of the dissolving tubs are transported to an adjoining room, where an assay sample is taken. Should the results of this assay show that the amount of silver remaining is less than 0°00036 of the weight of the material operated on, the residues are placed aside, for the purpose of being fused for blistered copper ; but if, on the other hand, they contain more than this proportion of silver, they are re-roasted by the workmen, without any further payment for labour. When, on the contrary, the assay shows a less amount of silver in the residues than that above stated, the roasters receive a bonus of the value of 12 per cent. on the excess of the precious metal extracted. The finely-sifted matt, after being withdrawn from the furnace, is allowed to remain about eight hours before being introduced into the lixiviating tubs, and thus becomes cooled down to about 160° Fahr. before charging. When placed in the tubs, hot water is admitted from @, until it begins to escape from the taps at the bottom. The water is then turned off, and hot liquors from a previous operation are introduced from the leaden cistern by the pipe 8, until the liquid flowing from the cocks at the bottoms of the tubs no longer affords a EE 418 SILVER. precipitate of chloride of silver on the addition of a weak solution of common salt. The final liquors collected in the vessel E, when they have become too highly charged with sulphate of copper, are brought in contact with scrap iron, and thus afford a supply of cement copper, which may be subsequently employed in the tubs ¢ and D. The process of Ziervogel is, however, adapted to the requirements of comparatively few localities, since the presence of certain impurities, and particularly of any considerable amount of either arsenic or anti- mony, gives rise to the formation of insoluble salts, which materially — interfere with the extraction of silver. In the Freiberg works, where the process was for some time experimented on, it was found that the presence of these substances so far interfered with the results obtained, that a notable amount of the silver present in the concentrated matts, invariably remained in the insoluble cupreous residues. As might be anticipated, by far the largest proportion of the silver is deposited in the first precipitating vessel, from which it is from time to time taken for the purpose of being purified and melted into bars. The principal impurities with which it is associated are the sulphates of copper and lime; together with a certain amount of metallic copper derived from the cement copper employed as a preci- pitant. The two former are removed by repeated washings with hot water, whilst the latter is partially dissolved out by treating the finely divided silver with dilute hydrochloric acid. The precipitate is subsequently refined in a furnace constructed for that purpose, and affords bars containing about 980 thousandths of silver. According to Lamborn, who carefully examined this process at the Mansfeld works, the cost of treating one hundred weight of copper, usually containing nearly } Ib. of silver, at that establishment, was -as follows :— By Liquationg es ss 2, yO ee of ALT OIAIATION 3 Sieh ag 2 ee a eaeaenna ,, Augustins method. . . ... . 4h, yy CACTY ODOUR Figs) 18 ais ty est a ae The amounts of silver remaining in the Mansfeld copper after treatment by the several processes are the following :— miter Liguation = 3°" ." eos)» omens zp th of one per cent, »y Amalgamation . . .. 2. % sq th 3 5 -Augustin’s method : -..4...°.8 oath BS ,, Ziervogel’s _,, iE ae Gin pees : VON PATERA’S PROCESS. 419 Von PatTerRA’s Process.—This method of extracting silver from its ores consists—Ilst, in roasting them with an addition of common salt until the whole of the silver has been transformed into chloride ; 2nd, in dissolving out the chloride of silver by means of a cold dilute solution of hyposulphite of soda; 3rd, in precipitating the silver in the form of sulphide by the addition of polysulphide of sodium; and 4th, in reducing the precipitated sulphide of silver to the metallic state by exposing it in a muffle, at a high temperature, to the ordinary influences of atmospheric air. The solution in hyposulphite of soda of the silver contained in argentiferous ores was first suggested in a paper published by Dy. Percy in 1848 ; and a translation of this having reached the Austrian chemist, it resulted, in 1858, in the introduction, at Joachimsthal, by Von Patera, of the process which now bears his name. The ores from that district are remarkable for the diversity of their constituents, and in addition to silver frequently contain various compounds of copper, lead, bismuth, iron, nickel, and cobalt, associated with sulphur, arsenic, and antimony. The veins inthe vicinity of Joachimsthal, though less productive thay formerly, still afford a certain amount of argentiferous ore of extraordinary richness, since the average yield of the whole quantity delivered at the works may be taken as affording about 2 per cent. of silver. Smaller quantities are not unfrequently worked containing from 5 to 6 per cent. of that metal, and as much as 15 per cent. of silver has sometimes been extracted from a parcel of ore. The fuel employed consists of lignite, coal, charcoal, and wood; the first of which is cheap and the second expensive, while the two last are becoming scarce, and growing every year higher in price. The price of labour varies from a shilling to one and sixpence per diem. Roasting.—The ores, which are prepared partly by hand picking and partly by concentration on shaking tables, are, on being brought to the works, subjected to a process of roasting in a furnace of a some- what peculiar construction, This apparatus, instead of having the long narrow hearth, broad firebridge, and short wide fireplace, usually employed for roasting sulphurous ores, has a hearth 9 feet 9 inches across, and measuring but 6 feet from the bridge to the flues leading into the chimney. The grate, which is only six inches in width, is four-fifths the length of the longer axis of the hearth, from which it is divided by a sort of firebridge, consisting of an iron tube covered with clay, and pierced with from ten to twelve small openings on the side EE 2 420 eos . SILVER. furthest removed from the fuel. A small boiler, set in brickwork near the furnace, supplies low pressure steam, which can, when required, be introduced into the tubular bridge, and allowed to escape in numerous jets over the surface of the roasting ore. The mineral to be operated on is introduced into this furnace in charges of four hundred pounds, and the heat slowly and cautiously raised, in order to prevent agglomeration of the particles. During this stage of the operation no steam is admitted, but, as soon as the charge has arrived at a red heat, the tap is turned, and as much steam blown into the hearth as can be safely introduced without so far reducing the temperature as to materially check the activity of the various chemical decompositions which it is desired to effect. At the expiration of four hours from the time of charging, the opera- tion is usually completed; and the ore, after being withdrawn and allowed to cool, is taken to a mill, in which it is ground to a fine powder, with the addition of from six to twelve per cent. of common salt, and two to three per cent. of sulphate of iron. A charge of this mixture, weighing three hundred pounds, is now introduced into a furnace similar to that above described, and is spread evenly over the surface of the hearth. This is raised to a red heat, and. the steam admitted as before, care being taken to keep the contents of the apparatus constantly stirred. The temperature is now gradually increased, and at the end of from ten to sixteen hours, according to the nature and richness of the ore, the operation is complete. The addition of sulphate of iron to the partially desulphurised ore is for the purpose of effecting the necessary decomposition of chloride of sodium, in case a sufficient amount of metallic sulphates should not be otherwise present. The introduction of aqueous vapours is found to facilitate the chlorination of the silver, besides greatly assisting in the condensation of the fumes and vapours in the cham- — bers interposed between the furnaces and the chimney through which the products of combustion finally make their escape. If this recovery of the substance carried off by the draught were not care- fully attended to, the loss of silver so caused would amount to about 10 per cent., and the economical treatment of argentiferous ores, by this process, be thus rendered impracticable. The roasted and finely- divided ore, containing silver in the state of chloride, is now taken to the lixiviating room for further treatment. LTixwiation with Water——The apparatus employed for the pur- pose of solution and precipitation will be understood by refer- VON PATERA’S PROCESS. 421 ence to Fig. 60, which represents a vertical section of the whole arrangement. In addition to chloride of silver, which is insoluble in water, the HH 2 CHAPTER XXII, TREATMENT OF ARGENTIFEROUS GALENA AT PONTGIBAUD, PREPARATION OF LITS DE GRILLAGE—ROASTING-—PREPARATION OF LITS DE FUSION —SMELTING IN CASTILLIAN FURNACE—IMPROVING OR CALCINING—CRYSTAL-_ LISING—REFINING—REDUCING—RE-SMELTING RICH SLAGS— ROASTING MATTS— TREATMENT OF CALCINED DROSS—TREATMENT OF LEAD CINDER—-TREATMENT OF LEAD FUME—LOSSES OF LEAD AND SILVER—SUMMARY OF COSTS. THe method of smelting employed at Pontgihaud affords an example of the treatment of highly silicious lead ores rich in silver.* These ores occur in large veins of quartz and feldspar traversing gneiss. The average produce of the ore, as extracted, scarcely exceeds 6 per cent. of lead, and consequently very large quantities must be passed through the different washing processes in order to obtain the amount of mineral, averaging about 50 per cent., which is annually smelted in this establishment. As much as possible, however, of what is * The gangues of the Pontgibaud ores are similar in composition to those of many of the silver-bearing veins of Mexico, Nevada, and other parts of the American Continent. We shall consequently describe, with considerable detail, the various operations conducted in that establishment, since the system there employed is well adapted for the treatment of argentiferous minerals containing a large amount of silica, wherever fuel and lead ores can be obtained at reasonable prices. The mines of Pontgibaud, Puy-de-Déme, France, have at various periods afforded large quantities of argentiferous galena, but were never so productive as at the present time. The re-working of the concessions was commenced by a local company in 1825, and the operations were continued under the management of French engineers until the year 1852, when the property was transferred to an Anglo-French Association, under the management of Messrs. John Taylor & Sons, of London. We were at that period for some time occupied in re-modelling the smelting works, and introducing into them various modern appliances, but great improve- ments have been since made, and more particularly in the apparatus employed for roasting the ores and their preparation for the blast furnace. The various ameliorations introduced into the system of treatment at Pontgibaud are, to a great extent, due to Mr. W. Hutchison, the present manager of the Smelting Works, to whom we are indebted for the drawings of the different furnaces, and for very copious and admirably arranged notes, affording the practical results of the several operations as now conducted. SMELTING——PONTGIBAUD. 469 called massif or cobbed ore is carefully selected, in order to avoid exposing it to unnecessary mechanical loss. Recently the proportion of massif to washed ore has become much greater than formerly, par- ticularly since the discovery of a new mine yielding ores very rich in silver. The effect of this has been to render the ores more refractory, since the assay of hand-picked ores for lead is seldom higher than 40 per cent., whilst the proportion of silicious gangue is much greater than in the washed ones. It is to the uniformly silicious nature of the Pontgibaud ores, together with the impurities contained in the work lead obtained, that many of the difficulties experienced in smelting them are due, and which have rendered necessary the adoption of the special pro- cesses employed at this establishment. These difficulties are further increased, particularly in the matter of cost, by the remoteness of the locality in which the mines are situated ; Pontgibaud being at a great distance from any centre of industry from which fuel and fluxes can be obtained at moderate prices. All the ores are delivered at the smelting works in a state of fine powder; that is to say, the coarsest will pass through a sieve with apertures of 4 m.m.in diameter. As many as seven varieties are received monthly from the different mines belonging to the com- pany. They vary considerably in richness, both as regards lead and silver, and the amount of gangue which they contain; this gangue is always silicious, although generally associated with small quantities of sulphate of baryta, arsenical pyrites, iron pyrites, blende, &e. | The produce of each mine is sampled on the 1st of each month, and immediately delivered to the smelting works ; where the operations are so conducted that all the ores received during one month may be converted into pig lead before the next month’s deliveries take place. This system, besides its convenience, has the advantage of enabling the smelter to check the calculated produce by the actual monthly returns. Each sample of ore is tried by two assayers, one on the part of the mines and the other on that of the smelting works; if their results differ to the extent of 1 per cent. each repeats his assays. In case of a constant difference, a sample is sent to a professional assayer, and the result he obtains is considered final; but this course is seldom resorted to. All the assays are made in an iron crucible, and when properly conducted yield results quite as high as those obtained by the humid 470 SILVER. way; a circumstance probably owing to the impurities in the lead button compensating for the slight loss by volatilisation. It will be necessary to bear this in mind, in comparing the losses of lead at the Pontgibaud works, with those experienced in other estab- lishments where ores of a different nature are treated, and where the assays are, generally speaking, less carefully executed. In the treatment of these ores nine distinct operations are necessary, V1Z. :— 1.—Preparation of Lats de Grillage. | 5.—Improving. 2.—Roasting. | 6.—Crystallising. 3.—Preparation of Lits de Fusion. 7.—Refining. 4,—Smelting in Castillian blast 8.—Reducing. furnace. 9.—Re-smelting rich slags. Tn addition to the above, the routine of the establishment renders four supplementary operations necessary, viz. :— a.—Roasting matt. b.—Treatment of calcined dross. c.—Treatment of lead cinder, d.—Treatment of lead fume. 1. Preparation of Lits de Grillage.—Although the ores do not differ materially as regards the nature of their gangues, they vary consider- ably in richness; and consequently also in the proportion of a ie matters present. It has, therefore, been found important, before commencing their treatment, to prepare a uniform mixture of the whole sampling. On this depends the regularity of the subsequent operations, and, in a great measure, their economical working. As it is impossible to thoroughly mix the whole weight of the various parcels of ore (often amounting to upwards of 300 tons), a lit of twenty tons, or a little more than the quantity usually roasted per diem, is prepared by weighing out, and spreading in thin layers, one above another, the exact proportion of twenty tons, which each parcel bears to the total weight delivered.* The “lit” being finished, the charges are made by successively cutting down with a shovel the pile of stratified ore; and in sucha way that every ton of the mixture removed shall have nearly the same composition as the entire mass. Experience has proved the advantage of this arrangement over that * Tons of 1,000 kilos, SMELTING——PONTGIBAUD. ATI of charging the hoppers direct from the several heaps in the ore magazine. The following will serve to show the kind of ore comprised in an ordinary monthly sampling :— ASSAYS. Dry ore. Lead Silver kilos. per cent. per M. kilos.* mo ashed ore “s..). 134,504 . . . ., 564 .» . 1°100 grammes. ee es F.0D ve oe A, ks OSD i Washed ore’. . 21,960 . . .°. 47% . « :1:137 . D.—Washed ,, . . Goda ttle: Gat se OGS yee) BGO © ae: Seen te en AN OT s. . ds) Syed «| 5 ee BU uy ev annen ore ft. I29,515 . toe TAD chon re, 1206 a et Ee 2002S a te O6E . - O'SRO s Total . . 300,798 To this mixture of ores are added the matts resulting from the previous month’s smelting in the blast furnace, which are, after being ground and roasted dead in a reverberatory furnace, treated exactly as ordinary ores. The total weight of matt mixed with the ores in the above instance was 35 tons, containing 14 per cent. of lead, and 400 grammes of silver per ton of 1,000 kilos. For preparing a lit de grillage of 20 tons, the proportion required of each of the above parcels (wet weight) was as follows :— Ore A.—8,094 kilos. Ore E.—2,454 kilos. Chiseog ye ae aoe Rei e0) bee 12 GPR ye Geom leaden D=- 576 Matt.—1,960 _,, ” 9 The average amount of moisture contained in these ores was 6 per cent. It will be observed that the proportion of roasted or calcined matt in the above mixture is about 10 per cent.; but this proportion con- stantly varies from month to month. The object of adding it to the lits de grillage is, that its oxide of iron may serve as a flux in the subsequent operation. In some cases, z.e. when the ores are more than usually quartzose, 10 per cent. of matt is found to be insufficient for this purpose, and ground scories de forge, or mill cinders, are added as a substitute: not unfrequently the previous month’s production of matt does not * The average produce of these ores for silver will be found to be about 39 oz. per English ton. 472 {33 SILVER. amount to 10 per cent., and then also iron slags are employed. As a rule, 10 per cent. of matt, or 15 per cent. of mill cinder, is sufficient, but it often happens that these proportions must be considerably exceeded. It would perhaps appear eater bis to add iron slag directly Mf the mixture prepared for the blast furnace, as is done in some other works ; but repeated experiments have led to the adoption of the method now employed; since its value as a flux in roasting, by the Pontgibaud system, is almost as great as its subsequent utility during the opera- tion of smelting. Two men are employed in the preparation of the roasting mixture ; they are paid two francs each per day, and in that time prepare és mixtures, and charge each furnace with eight tons of ore. The cost of this operation is 0:25f. (24d.) per ton. 2. Roasting—The ores are roasted in very large yee furnaces worked from both sides. There are three of these at Pontgibaud, but two only are in constant operation ; all have exactly the same form and dimensions; their great width, as well as their great length, is a most dtc: ios as regards economy of fuel, Fig. 75 represents an elevation, Fig. 76 a horizontal section through — the working doors, and Fig. 77 a vertical section, on the line x ¥} of the roasting furnace. The exterior is built of cut lava, and the sides and roof of firebrick; the sole is laid with hard common bricks. The outside is plated with iron between the bottoms and tops of the doors a, b, as shown by the horizontal lines. The doors a nearest the fireplace are a little smaller than the others. The fireplace a is divided from the fusing hearth B, by a firebrick bridge 20 inches in width ; the ore being admitted into the hearth c, through the hoppers D. The bottom #, beneath the lining of common bricks, is com- posed of a mixture of sand and slag well beaten in. The tap hole is shown at c, Fig. 77. This apparatus requires but little repair. Fia. 75. A iin Te = eheeaill= = iad il ‘i Roasting FURNACE. ( Elevation.) Bits 7 Bs ali ‘ , ———— SMELTING—PONTGIBAUD. 473 When working, this furnace contains six tons of dry ore and matt, divided into three charges of two tons each, severally occupying about one-third the surface of the entire sole. There are six doors on either side, two of which correspond. with one or other of the charges, and enable the workmen to turn or advance the ore when required. es eT a oN: ee Oe a RoastTine FURNACE. (Horizontal Section.) RoastTinec FURNACE. (Vertical Section.) The different parts of the furnace occupied in succession by each charge may be distinguished as follow :— 1st.—Drying bed, immediately under the hoppers. 2nd.—Desulphurising or oxidising bed, widest part of furnace. 3rd.—Agglomerating bed, next to fireplace.* The first two are on the same level, the third about 20 em. lower than the others. . The peculiar form of the agglomerating or fusing bed has for its object the equalisation of the temperature over that portion of the furnace in which the greatest heat is required. The ore arriving on this bed is fused and run out in the form of * The agglomeration of the ores at Pontgibaud is in reality a fusion, without reduction. 474 3 SILVER. a liquid slag. At intervals of six hours a charge of melted ore is with- drawn, and the other charges in the furnace are advanced a stage ; whilst a fresh charge is let down through the hoppers upon the drying bed. The time each charge remains in the furnace is consequently 18 hours. Eight tons of ore and matt are thus roasted in each furnace in the course of 24 hours, with a consumption of about 2,000 kilos. of coal, and 6 per cent. of lime. The consumption of iron slags averages 7 per cent. ; but, whatever the proportions of this flux, or of lime, may be, the quantity of ore charged remains constant—that is to say, 1,800 kilos. | Four men are employed at each furnace, per shift of twelve hours : the foreman is paid 2°20f. per day, the others 2f. The general system of roasting in this furnace will be understood from the foregoing description; but, in order that it may be fully comprehended in all its various details, it may perhaps be necessary to explain the mode of working more minutely. | Let us, for this purpose, suppose that the usual regularity of the operations has been uninterrupted during the night, and that at six in the morning we accompany the men to their work. We shall find the bed next the grate empty, the charge having, about two hours previously, been run out upon the floor, on one side of the furnace. The charge in the middle bed having been roasted dead, is heaped up in the throat ready for being advanced into the agglomerating bed, which is still at a red heat, although the fire has been allowed to burn down in the grate. The foreman begins by throwing a shovel- ful of coals on the fire to create a blaze and light up the interior, so that the men may see their work. All hands then commence busily advancing the ore with long paddles. Two men advance it upon the agglomerating bed, and pile it up as near the bridge as they can; whilst two others push forward the ore from the drying bed into the middle or desulphurising hearth. In the latter, the ore is spread evenly over the sole, and two or three shovelfuls of slaked lime are afterwards scattered over its surface ; especially on the side next the fire, to prevent the formation of a crust of partially-agelomerated ore very difficult to calcine. | ; The time required for advancing the two charges is about forty minutes. A new charge is now let down from the hoppers D, and spread over the drying bed with a rake. The doors are then all closed, the grate charged with coals, and the fire increased until the furnace has acquired a bright red heat. SMELTING—PONTGIBAUD. 475 In about three quarters of an hour the ore in the middle bed has become sufficiently hot to scintillate when stirred, and to give off sul- phurous acid vapours. Two men, one on each side, now commence turning over the charge with paddles, which they do repeatedly, first forwards towards the fire, and then backwards towards the flue; taking care that the whole of the ore is turned, and that fresh portions are constantly exposed to the action of the heated air. From time to time a shovelful of slaked lime is thrown in and worked up with the ore to keep it “dry ;” especially on the side next the fire, where it is most liable to clot. The operation of turning is continued without interruption until the charge in the agglomerating bed is ready to tap, when, during the time of tapping, &c. there is an interval of nearly half an hour; but it is afterwards renewed and continued until the expiration of six hours, or at least until the ore has been roasted dead. When the mixture of ores is good, 7. e. when it is moderately rich in lead, and contains at the same time a good deal of oxide of iron, the charge in the agglomerating bed requires but little working. It then melts easily, and in about two hours and a half after the firing com- mences it is ready to draw. But, should the mixture contain an excess of silica, it is difficult to get the ore into a liquid state. Part of the charge attaches itself to the sole, and another portion is drawn out, after great trouble, in a tough pasty condition, A great loss of lead, and considerable waste of fuel, are the consequences. For this reason it is advantageous to add oxide of iron to the ore, and the cheapest way of doing this, at Pontgibaud, is in the form of iron slags, although their cost is 27f. per ton. Assuming the charge worked to be easily fusible, it 1s only re- quisite to paddle it once towards the bridge; about three-quarters of an hour after beginning to fire. It is also necessary, just before tapping, to rake over the bottom, to be certain that none of the ore is sticking to it, and that the whole charge is perfectly fluid. When this is found to be the case, the tap hole is unstopped, and the charge run out upon the floor; where it is prevented from spreading beyond certain limits, by a small dam or ridge of ore and sweepings, &c. reserved for that purpose. No lead is reduced in this process, but a certain quantity of very rich sulphide of lead is generally met with at the bottom of the charge. This is particularly the case when the ore is rather rich in lead, and has been imperfectly roasted. The bulk of the charge of roasted ore is composed of a clean black slag containing from 30 to 40 per cent. of lead. The whole of the 476 SILVER. sulphate of lead formed in the middle bed is subsequently decom- posed by the silicic acid present. As soon as the charge has been run out, the tap hole is examined, and any adhering ore is cut away with a long chisel ; after which it is again stopped. The bridge and sides are then looked at to ascertain whether they require repairs; since holes are often eaten out by.the melted ore, which require to be stopped with clay after almost every charge. The fire is now suffered to burn down, to allow of clearing the grate of clinkers, The damper is at the same time partially closed, and preparation is made for the advance of another charge, when the time for doing so shall have arrived. Charge thus succeeds charge at regular intervals of six hours: the loss of weight in roasting amounts to about 10 per cent. of the quantity charged. The loss of metal by volatilisation is extremely difficult to estimate, as it 1s scarcely possible to obtain a fair sample of the roasted ores. Several experiments, undertaken with this object, have fixed the loss of lead at from 2 to 3 per cent. of the total quantity present. The loss of silver is still more difficult to determine, and no result which can be depended on has yet been obtained. The cost of roasting ore per. ton is as follows (the dry ore per charge being 1,800 kilos.) :— oe Coal, 280 kilos, at35f. 6 2) a 1. 8 9 80F Lime, GO 55 [Ab DA Ee ois ears) Perea Seories de forge, 70. Saher? o) 2k) er eee 1:90 Labour . Boe ys ; ; ie Tools and repaits. > 2c 2 ARE at) he 4) Sundries (including superintendence). . . . _ . 2°90 F. 19°75=15s. 9.6d. 3. Preparation of Lits de Fusion—The lits de fusion are usually composed as follow :— PLORMCU ORE Te ee ee ee 10,000 kilos, erop lee ashe Ty oy Gee ee LOOUs ss, Pimestene 2.7 ei. eel dct eee 16002, ino Ma pars sear aus oi is tear) oh 300 99 The above figures give the average quantities of flux in the furnace mixtures. They are, however, modified with the nature of the ore; the proportions of limestone and fluor Spar varying most considerably. Two men are employed at this work, and receive 2f. each per day. They prepare a lit and a half in that time—15 tons SMELTING—PONTGIBAUD. ATT consequently the cost is 0:27f per ton of roasted ore, and 0:25f. per ton of crude ore. 4, Smelting in Castillian Furnace.—There are two of these at Pontgibaud, but it is seldom that more than one is in blast at a time. Fig. 78 represents a front elevation of one of these furnaces, which are constructed of cut lava, and are very inexpensive to build. Fie. 78. Bea STUUANUOUONEROUUUON WOOD ION ENON ON OOOO OOOO OOOO OPO OOO CONDON OOOO OOOO COCO CO CCL if | = LLL TA l TTT Se TUT ONVTUNVTCOCIU MANY UDUVTOUNUIQIOUEETTIT UNS TLELA Lat ALLL ! | L | —- ! il CASTILLIAN FuRNACE, PONTGIBAUD. (Front Elevation.) Their height from the slag-overflow @ to the charging door is 5 feet, internal diameter 35 inches; diameter of tuyere 3 inches ; pressure of wind about 4 inches of water. These furnaces are supplied with the blast by the nozzles }, of which there are three, connected with the mainc; water tuyeres are not employed in the Pontgibaud furnaces. The mode of charging is similar to that employed for other furnaces of the same kind. The ore is distributed around the sides, the coke in the middle and 478 SILVER. against the breast. The furnace is kept constantly full, and particular care is taken not to let the flame appear above the charge; it being considered important to keep the top as dark as possible. - A large breast pan, capable of holding 20 pigs at a time, is preferred, but it is sometimes difficult to maintain it of that size. ‘From 14 to 16 tons of ore are smelted in 24 hours, with a con- sumption of one ton of coke, or about 7 per cent. of fuel. The quantity of lead obtained in the same time is from 100 to 120 pigs, or from 5 to 6 tons. From 7 to 10 per cent. of matt is also produced. ; It is found that the production of a certain quantity of matt cannot be prevented. Indeed its presence is regarded as being in no way prejudicial to the working of the furnaces, unless it be formed in too great an excess. When very little matt is produced, the slags are generally rich in lead. Sulphide of iron appears to act on the silicate of lead as a powerful reducing agent. Whenever oxide of iron does not abound in the ores smelted, the presence of matt alone does not prevent the slags from becoming rich. The presence of a large quantity of oxide of iron is indispensable to the production of poor slags, since without it the oxide of lead remains combined with silicic acid, and cannot be separated therefrom. It has been found by analyses of poor slags that those most easily freed from lead contain at least 40 per cent. of oxide of iron. This base may be however, in part, replaced by lime, especially if fluor spar be at the same time added. Yet, although by this means poor slags can be obtained, they are never so poor as when oxide of iron is present in slight excess; the amount of lead volatilised is also con- siderably increased. The proportion of slags produced is from 65 to 70 per cent. of the ore smelted. The slags formed under the most favourable circumstances do not contain less than 2 per cent. of lead. When they exceed 3 per cent. they are re-smelted in a furnace of similar construction to those already described, but situated in another part of the works. The slags, as they flow from the furnace, are received into cast iron waggons, which, when full, are drawn away to the waste heaps on a small tramway constructed for that purpose. The waggons employed at Pontgibaud, of which Fig. 79 is a side view, Fig. 80 an end view, and Fig. 81 a plan, are very convenient in form, and but little liable to break. The depth of the pan is 20 inches, and its width 21 inches. SMELTING—PONTGIBAUD, 479 These have been in constant use for the last five years, and have scarcely ever needed repairs, except to the wheels and axles. Fig. 80. SipE VIEW OF SLAG WAGGON. PLAN OF SLAG WAGGON, The men employed at this furnace per shift of 12 hours are :— Piboreman, 1) mit ef paid! «-..« 2:50f. per day, 1 Charger sa Pe ee wat 3 Trammers 37 each ~. 1°80 99 9 The costs per ton of roasted ore are as follow :— Tron LO Rilos as 95f epee Seti feet eel Tumestone 160-7,;> a20f oe oN Pao 'e : 220 Einowepar oO). GbOl. oe «oh Gee ose’ YAO Coke i ial. bet ee ones) | OOO PAoutCaly eeu eka ont. ae FOS ey aay lst) OE8D Tome andirepaits oe tes. bas howl aia dope 2+ tim O75 Sundries (including superintendence) . . . . . 3°35 F, 23°40=18s. 86d. 480 : SILVER. _ The cost per ton of wnroasted ore is therefore 21-06f. or 16s. 10-1d. The cylinders of the blowing machine are 1°34 m., or 52 inches: in diameter. Length of stroke, 52 inches. Number of strokes per minute, 12. The lead obtained from the Castillian furnace contains nearly all the silver originally present in the ores smelted, excepting a small proportion combined with matts, or retained in the slags. The usual assay of matt is from 15 to 20 per cent. of lead, and 400 to 500 erms., or from 12 oz. 17 dwt. to 16 oz. 2 dwt. of silver per ton; the average assay of the lead is about 3 kilos. =964 oz. per ton. The whole of the silver in the matt, and a portion of that in the slags, is recovered in the subsequent operations; but a small fractional part of that metal is nevertheless unavoidably lost. This loss amounts to 10 grms., or 6$ dwt. per ton of slag, or 0°568 per cent., according to assay, of the total quantity contained in the ores. A certain amount of silver is also volatilised with the lead, but how large a proportion is, from this cause, entirely lost cannot be accurately ascertained. That it is, however, exceedingly small is probable, from . the known properties of silver, and the small amount found in the fumes collected in the flues and condenser. The proportion of silver thus volatilised or mechanically carried off, and again recovered, in all the different processes, including cupellation, amounts to only 0-470 per cent. of the total quantity, according to assay, contained in the ores. The loss of lead in smelting ores in the blast furnace amounts to about 17 per cent. of the total quantity contained in them. It has been ascertained that about 5 per cent. of all the lead is retained in the slags, and about 12 per cent, carried off in fumes. Two per cent. is, however, afterwards recovered from slags by re- smelting, and about 34 per cent. from the fumes. The actual loss, therefore, in the operation is equal to 11? per cent. of the total quantity of lead contained in the ores. It will be seen from the foregoing that the system of roasting and smelting at Pontgibaud has undergone very important alterations since the publication, in 1851, of Rivot and Zeppenfeld’s “ Description des Gites Métalliferes &e. de Pontgibaud,” which appears to be still regarded by many continental engineers as a description of what is being done at the present time. In proof of this it may be stated that in a lengthy paper on the Metallurgy of Lead, published in the “Revue Universelle des Mines,” so recently as 1863, the engraving of a SMELTING—-PONTGIBAUD. 481 roasting furnace shown in Rivot and Zeppenfeld’s work is reproduced as though it were still in use; whereas, in point of fact, it had been demolished ten years previously. It is, however, in the treatment of the argentiferous lead obtained that the system now employed differs most essentially from that in use in 1851, At that period, the whole of the lead obtained from the blast furnace was immediately cupelled in a large German cupelling furnace, and the silver separated and refined in the usual way. The litharge produced was afterwards submitted to a complicated mechanical pre- paration in order to render it fit for sale; the whole, or very nearly the whole, of the lead thus converted into oxide being sold in that state. The small quantity of metallic lead sent to market was obtained, after great loss, by the reduction of a portion of the litharge, and was of very inferior quality. At the present time it would be extremely difficult to find a sale for so much litharge as the Pont- gibaud works could now produce, as the yield of the mines has been enormously augmented. There is, however, never any difficulty in disposing of pig lead. In the method employed at Pontgibaud since the works have been under the direction of Messrs. John Taylor and Sons, the object in view has been to convert the whole of the lead into metal of first-rate quality, and to obtain at the same time as complete a separation as possible of the silver: this is accomplished by means of Pattinson’s process. The advantages of this method have been long appreciated both in England and on the Continent, and it is now generally adopted, either in com- bination with the old continental method, or with some modification of it suitable to the locality and the nature of the ores treated. The principal advantages of Pattinson’s process, as compared with the old Pontgibaud method, are the following :— 1st.—Direct production of metallic lead. 2nd.—A greatly diminished loss of metal. 3rd.—A higher yield of silver. In the treatment of the argentiferous lead obtained from the blast furnace, four distinct operations are necessary, viz. :— Improving or softening. Crystallising. Refining. Reducing. 5. Improving or Calcining—The whole of the work lead produced at Pontgibaud must be purified before it can be treated by Pattinson’s Tek 48? SILVER. process, and this is done by exposing it at a low red heat to partial oxidation in a reverberatory furnace specially adapted for that purpose. The chief impurity contained in the lead is antimony; the others are sulphur, iron, arsenic, and copper. All are in relatively small proportion, but are still in sufficient quantity to render the lead hard. The accompanying drawings, Figs. 82, 83, and 84, show the arrange- ment and dimensions of the furnace employed. Fig. 82. IMPROVING FURNACE. (Elevation.) Fig. 82 is an elevation; Fig. 83 a horizontal section at the level of the top of the pan; and Fig. 84 a vertical section through the tap hole. The fireplace A is separated from the pan B, by a bridge 3 feet 3 inches wide, and the furnace is provided with two doors 0, through which the dross may be removed. In principle this resembles the ordinary softening furnace with its cast iron pan, but its greater size and solidity of construction render it much more economical than the furnaces usually employed for the purpose. On reference to the drawing, it will be remarked that the pan is not only much larger than those commonly employed, but has also a rounded form ; the object in giving it this shape being to diminish the tendency to crack, to which all square-sided pans are so hable. Another essential feature in the construction of these furnaces is to make them perfectly lead-tight, in case the iron should break. This is most effectually done by setting the pan on a bottom of well- beaten brasque two feet in thickness, resting on a solid foundation of masonry. The sides of the furnace must be either of thick iron plates or of large cut stones. In either case the space between them and the pan should be at least a foot wide, and well filled with hard beaten brasque. The lead is tapped from the pan.through a small hole a, ‘hies SMELTING—PONTGIBAUD. 483 fourths of an inch in diameter, bored in the bottom of the pan, and communicating with a thick cast iron tube 0’, fastened to it by means of stud-bolts screwed into about half the thickness of the metal. Before charging, the hole in the bottom is plugged by a long Fig. 83. IMPROVING FURNACE. (Horizontal Section.) pointed bar passed through an opening ¢, Fig. 84, in the roof, corre- sponding with the tapping hole, and placed vertically over it. This bar will not generally stop the hole quite tight ; especially after the furnace has been working a long time. The tube is, therefore, partly filled with bone-ash, firmly rammed in; a bar having been previously Fia. 84: WV x / IMPROVING FURNACE. (Section through Tap Hole.) placed in the tube in such a way that the channel left, after its with- drawal, shall correspond with the hole in the pan.’ This horizontal I12 484 SILVER. bar is even more necessary than the vertical one; the use of the latter being to take off the pressure of the lead in the pan, and regulate the flow of metal in tapping. The horizontal bar is put in and withdrawn by the aid of a sledge; in much the same way as, though more easily than, a tapping bar at the blast furnace. ; Two of these furnaces have been erected at Pontgibaud; one for common work lead, the other for the hard lead reduced from calcined dross. The former has been almost constantly in use for upwards of five years; and although the pan is now cracked, the furnace 1s as tight and serviceable as ever. Both improving pans were originally lined with bricks, as shown in the drawings, Figs. 83 and 84, to protect the iron from corrosion by the oxides formed on the surface of the metallic bath. This precau- tion is now thought to be unnecessary ; all that is required being to avoid overheating the furnace, and the consequent fusion of the dross. It is also found that a dull red heat is the best tempera- ture for calcining Pontgibaud lead; and at that point the oxides neither melt, nor exert any corrosive action on the pan, especially if ¢ little lime be from time to time added. The usual charge of a pan without lining is about twenty tons. The brick lining diminishes its capacity by about one-fifth. A charge of twenty tons of common work lead requires sixty hours to become sufficiently soft for treat- ment by Pattinson’s process, the whole time necessary for the operation, including charging and discharging, being three days. Three men are employed in filling and emptying the pan, and are paid 2f. each per charge. The pigs of lead are introduced through one of the working doors by means of a long charging bar, and the charging is effected with great ease and rapidity. Except for charging and discharging, scarcely any labour is required, as the firing is attended to by one of the men working at the Castillian furnace. An ordinary month’s work at this furnace is as follows :— Percentage Work Lead in. Soft Lead out. of soft Lead Dross. Coals consumed. Lime used. Tons. Tons. obtained. Tons. 5 ilos. 139°150 131°528 94°7 8°675 11°560 554 The small consumption of coal is partly due to the employment of cinders picked out from the imperfectly burnt ashes at the pots, and mixed with the coal ; their cost per month being equal to a boy's wages, viz. 20f. per month. The cost of calcining one ton of blast furnace lead 1s— SMELTING—PONTGIBAUD. 485 Coal, 83 kilos. at 35f. 7 Setanta’ oh ZOO ee ee a hls oa ea hy Oo O'1G PeGry Oe RIORL Ab OAL nee 0-18 SEerOUr See ee Peers a ee AR EePCLEiPGear ee. eee Cee tS) ee EE Ce EG —__. F. 4°28=3s. 4:8d. Cost on ton of ore 1°90f.=1s. 6°2d. The drosses resulting from the calcination of the work lead con- cain, besides the various impurities, a large proportion of lead, par- tially in the form of oxide, and partly in the metallic state. These drosses are subsequently treated in the reducing furnace. The lead reduced therefrom is very impure and exceedingly hard, and, as it contains a considerable proportion of silver, 1,400 erammes, 45 oz., per ton, it is again calcined in the ordinary way. The hard lead obtained in the treatment of the lead cinder left as a residue in the reduction of litharge and pot dross is also calcined in the same furnace, The hard lead contains a large amount of antimony and other impurities very difficult to separate, and consequently the process of softening in this case becomes long and costly. The average time required for calcining 20 tons of hard lead is about four weeks. The usual quantity treated per annum, with results and costs, is as follows :— Percentage of Hard Lead in, Soft Lead out. soft Lead Coal consumed. Lime consumed, ons, Tons, obtained, Tons. Tons. 148°845 96'978 65'1 99900 5 Cost per ton of Hard Lead. One aks AOL, 5. s ay xy Boost, Viie ee oon at edt, Ug. O8O RARE PERE IR ae SEAR erent ee EL een | Ca , F, 24:50: 19s. 7:2. Cost on ton of ore smelted 1°03f. = 9°6d. The dross skimmed from this hard lead yields on reduction about 55 per cent. of a very hard lead, assaying 600 to 700 grammes, 19 oz. 5 dwt. to 22 oz. 10 dwt., of silver per ton ; which is generally mixed with the ordinary hard lead and treated in the same way. In the statement of costs, all the hard lead, of every kind, is included. Occasionally, when a sufficient quantity has accumulated, it is worked separately. It then gives a dross which on being reduced yields an extremely hard lead. This, whenever it contains too little silver to 486 SILVER. pay the costs of extraction, is immediately disposed of for making certain alloys containing a large quantity of antimony. But this seldom happens, as it is only after repeated calcinations and reduc- tions that a hard lead is obtained too poor in silver to pay for again working over. The proportion of poor hard lead produced at. Pont- eibaud is therefore exceedingly small. 6. Crystallising.—At Pontgibaud there are twelve pots in one set— eleven ten-ton pots, and one six-ton, or market pot. The system of working is by thirds. The ladles used are 20 inches in diameter, and 6 inches deep, and of the ordinary English pattern. The cranes employed are also of the usual form. The average assay of the work lead is, as before stated, about 3,000 kilos., 964 oz., of silver per ton. It is charged in the tenth pot. The usual assays of the whole series of pots, tops and bottoms, are as follow :— oh tee SILVER PER TON. | Pot. — = Remarks. Top. Bottom. grammes. oz. dwt. gr. eracimess on dwt. gr. a I 15 9 15 opie sail Poor Lead. eae 30 19 7 60 118 14 eae 60 118 14 120 Bie gee fo 120 S172 220 cae tae 8 pee BAA RO 7 FON 400.7) 18 RS 6 400 19°17. 5 720 23 3 0 7 700/392 10. 3° e200) Se eer 8 1,150 36 19 12 1,800 57 17 12 9 1,850 59 9 16 2,900 93 4 21 10 | 3,000 | 96 9 4 | 5,000 | 16015 8 | Charging Pot. 11 5,200 | 167 38 22 8500 21° 273.290 val 12 6.5000) 97a. 6-1. 146.000 1 5i4e 9 of Rich Lead. In working the rich pot, the whole of the bottom is not ladled out; it is found to be more advantageous to ladle out the liquid only, and - leave the crystals behind. When the ordinary quantity, or about two- thirds, of the lead has been turned into the eleventh pot, the remain- ing one-third consists of a mixture of crystallised and uncrystallised alloy. The latter, being much richer than the former, is separated as completely as possible; and this portion only, amounting to a little more than half the bottom, is sent to the refining furnace, SMELTING—PONTGIBAUD. 487 The work of removing the liquid is readily effected by means of what the French workmen call a panier, which is made of a piece of sheet iron, pierced with numerous small holes, turned up and fastened with rivets in the form of the frustum of an inverted cone. It is provided with two handles for putting it into and taking it out of the pot. By its use, a well is readily formed in the middle of the crystals, which facilitates the draining of the liquid metal from the surrounding mass, and allows of the lead being easily ladled into moulds. The right moment for introducing the panier, and ladling out the liquid, is easily determined by practice. When it 1s desired to take out much liquid metal, the pot is, on approaching the bottom, worked thin; but when the contrary is required, the work of stirring is continued until the crystals have become thick. In all cases, it is necessary to remove the whole of the liquid lead, otherwise the crystals left behind may be too rich. The proportion of rich lead, viz. 18:2 per cent., cupelled at Pont- gibaud is necessarily large, as the original lead is itself comparatively rich in silver. It is, therefore, very important to concentrate the rich alloy as much as possible before taking it to the refinery, where it is necessarily exposed to considerable loss from volatilisation. Experiments made by Mr. Hutchison, with the object of enriching lead to a much higher degree than is usual, have demonstrated the impossibility of doing so beyond 2 per cent. of silver; and this degree of concentration is only attained after repeated and very care- ful crystallisations, and by at last drawing off a small quantity only of liquid alloy. When the converse of this operation is tried—z.e. when lead, enriched in the cupelling furnace so as to contain about 8 per cent. of silver, is fused in a pot, and cooled down in the ordinary way, the portions which first solidify are much richer than the liquid drained from them; the latter, after repeated drainings, invariably containing about 24 per cent. It therefore appears that the remark- able property of crystallisation, discovered and utilised by Pattinson, arrives at its turning-point when the lead has acquired a richness of from 2 to 24 per cent. of silver.* In the ordinary way of working, it is remarked that in proportion * Mr. Hutchison remarks: “I have never seen any explanation of the reason for stopping the concentration at from 400 to 600 oz. per ton. We are generally told it would not be economical to push the concentration further ; but this is not altogether true, as further concentration would certainly effect a saving of a part of the lead now volatilised during cupellation.” 488 SILVER. as the concentration advances, it becomes more and more difticult to obtain the same degree of enrichment per pot or per ton of lead crystallised which is possible with poorer lead. An ordinary months work at the pots may be tabulated as follows :— CHARGED, OBTAINED. J Y a. aH a Calcined Reduced Market Coals Lead. Lead, Total. Lead. Rich Lead. consumed. Wages. Tons. Tons. Tons. Tons. Tons. - Tons. f. 135°000 63°000 198°000 130°000 23°400 61°000 960 Four pairs of men are generally employed, whose time is divided into twelve-hour shifts. Four, and sometimes five, pots are worke.. by each pair per shift. The crystallisers are paid 0-60f. each per pot, and the stokers 2f. per shift. The cost of crystallising per ton of market lead produced is as follows :— Coal, 470 kilos. at 31f.2. °°. J a Wages SON OTe ees ne ea Wear and teat-of potsio' 2) eo 2 Skt ee Tgols: and, tepairs: «Fed ston ¢ AeA eee ee Sundries, including superintendence . . . . 4:00 F’. 28:27 = 29s. 7°4d. Cost of crystallising per ton of ore, 12°39f. = 9s. 10°9d. The loss of lead in the process of crystallisation proper is trifling, as the losses incidental to the process chiefly occur in the cupellation — of rich lead and the reduction of drosses, and will be indicated under their respective headings. There is, however, a certain loss of silver in the market lead sold, since it invariably retains about 15 grammes, 9 dwt. 15 gr., of silver per ton; but this quantity amounts to only 0'533 per cent. of the total weight of silver contained in the ore according to assay. 7. Refining —The ordinary English furnace is employed at Pont- gibaud for the cupellation of rich lead. The operation is conducted in the usual way, except that the tests are deeper than those generally used, About four tons of rich lead are passed in twenty-four hours ; but a certain quantity, amounting to one-fifth, is tapped out about every eight hours, or whenever the lead in the cupel has attained, by concentration, a richness of about 8 per cent. of silver. The bottoms of enriched: lead thus accumulated are cupelled, as usual, at the end of the operation. About 15 tons of rich lead are usually worked at one time, and a plate of silver, weighing from 240 to 250 kilos. (7,720 to 8,042 oz.), is obtained. When cleaned, the silver is tapped at the ini! Pe eerie ae ae Tae en eee SMELTING—PONTGIBAUD. 489 back of the test into moulds, and afterwards melted down in large black-lead crucibles. It is then cast into ingots of from 20 to 25 kilos. each, suitable for the market. These ingots contain 999. thousandths of silver. The cost.of cupellation per ton of rich lead is as follows :— Coal, 290 kilos.at «= BHF. wk. 10°15f. etsh oer abe ral ey ee Pe a7 Pearlash 0°17 ,, at 1,765f. PRR Ot. 030 ene eee eR ee stk Ate: Ce olen al Aw O80 ener eee ee sg ee ty od ODE, BC os epee a ala i ier i Pea me a F, 27°45 = 21s. 11°5d. Cost of refining per ton of ore smelted, 2°27f. = 1s. 9°8d. The loss of lead in refining is about 7 per cent. of the weight of lead worked, or 1:252 per cent. of the total work lead obtained from the blast furnace. The loss of silver volatilised with the lead vapours, although very minute, is probably greater during cupellation than in any of the other processes. Its amount cannot be determined with accuracy. 8. Reducing—The furnace employed for reducing the litharge, pot dross, and calcined dross, is similar in form to the Welsh rever- beratory furnace, but has only four working doors, two on the back side, and two on the fore side. Its principal dimensions are as follow :— m. fie iti GEE Height of furnace Io 6488 VA », from fire-bars to ie i brides ale a3 », bridge to crown of arch. 0°25= 0 98 / Width of fireplace yd Ser ay, Length 3 te tse ee ee 1 MreeOr ridges 00 oh 2s GO eee Le LG Pe 016m lee. OFF hae ae a oe TO AST TG yeraee width of do. 2 1.) .. . 280== 9. 2°2 In the reduction of htharge and pot dross the operations are con- ducted in the usual way. The average cost of reducing one ton of litharge and pot dross is— ante Aloe Ai BOL es peut Paes ayo QOL EEE Re OE ere ee el a rad i Os Tools and repairs . . . eee URAC Sundries, including gipariitentenoms ees LOO ey oe — ben Lipa. } Cost on ton of ore, 1°73f. = Is. 4°6d. 49() SILVER, Nearly one-third the weight of market lead produced is skimmed off the different pots as dross, and passed through the reducing furnace. This large proportion of dross is due to the richness of the lead worked, and the consequent repeated crystallisations to which it must be submitted. The proportion of litharge reduced is.nearly the same as that of the rich lead refined. The total weight of lead reduced from pot dross and litharge, and returned to the pots, is equal to nearly one-half the market lead made. 9. Re-smelting rich Slags—The slags are smelted in a blast furnace of similar construction to those employed for smelting the ore. About 260 tons are smelted per month, and are derived principally from the ores actually worked during that time. Their average assay for last year was 34 per cent. of lead. The slags, after passing through the furnace, are thrown away, but still retain about 14 per cent. of lead. A very large proportion of the lead they contain is volatilised, but part of it is afterwards recovered in the flues, though in what proportion it is impossible to ascertain. Only 1 unit was obtained last year as pig lead (assay 750 grammes of silver per ton), and yet it was more than sufficient to pay the expenses of treatment; the fume collected in the flues of itself affords a fair profit. At present the slags are far too poor to make it advantageous to melt them over again, and it is probable that as the slags produced direct from the ore are gradually obtained poorer, this process will either be abandoned altogether, or only employed when the accu- mulation of rich slags may render it desirable. The costs of smelting one ton of slag are the following :— Coke, 100 Kiloge:! tf) (4 a ie oe ee Dmeltera wages oa ilct! at Be eee Tools:and. repairs (5 0). ok ee Cartage and breaking § 2°.) . os.) . ee —_—_—. F. 6°92 = 5s. 64d. Cost on ton of ore, 6°10f. = 4s. 10°6d. SUPPLEMENTARY OPERATIONS. a.—Roasting Matt.—The matt produced in the blast furnace is re- turned to the ore magazine, and mixed with ores in the “Lits de Grillage,” as already explained ; but before being mixed, it is ground in a mill to a coarse powder, and calcined in one of the reverberatory furnaces employed for roasting ore. A charge of matt weighs 24 tons ; each charge remains in the furnace double the time allowed for ore. SMELTING—PONTGIBAUD. 491 Every twelve hours a charge is withdrawn, and a fresh one intro- duced. The matt is worked on the bed next the fire, and as soon asa charge has become sufficiently hot, which takes place after about half an hour’s brisk firing, it is, uninterruptedly, turned with paddles, during the whole time. Rapid oxidation of the metallic sulphides then commences; and as sufficient heat for calcination is thereby maintained, the fire in the grate is allowed to burn down, but not to go out, since in that case too much cold air would enter the furnace, and lower the temperature of the charge. When the charge has been properly calcined it becomes almost black, contains very few lumps, and emits scarcely any sulphurous fumes. It is then drawn through the working doors, by means of iron rakes, and is thence removed to the ore magazine. The cost of roasting one ton of matt is as follows :— PRISE MALS p20 dts ge oe pk day wy ceed: Ce ong Se as Pag te ee eri ae gamer oo 8 Crewing and cartyve, 9s. «6 tess @ Feo O00 Cost of roasting matts on ton of ore, 1°05f. = 10d. b.—Treatment of Calcined Dross—The drosses skimmed from the work lead, and from the hard lead in the process of improving, are treated in the reducing furnace, and the residues smelted in the blast furnace. The object of this preliminary operation is to separate all the metallic lead by eliquation, and to reduce as much as possible the amount of the material to be treated in the Castillian furnace. It has been found that this is best effected by working it in small charges mixed with a certain proportion of fine coal. Five tons, divided into four charges of 1} ton each, are usually worked in twenty-four hours. The charge is turned and frequently paddled to facilitate the drainage of the lead from the mass, which acquires, after a short time, a rather pasty consistence. The cinder drawn out on the floor at the end of each operation is subsequently smelted in the manner. described under the head of “ Treatment of Lead Cinder.” About 56 per cent. of hard lead is thus obtained, with a consumption of 30 per cent. of coal. The cost per ton of stuff is as follows :— 30p kilos: atipeth es), Pow eee Be. 1 0°68E. Vif ee oe ao (OF “0 kee F12°90's— 10s) aa. Cost on ton of ore, 0'68f. = 6°5d. 492 SILVER. e—Treatment of Lead Cinder.—These residues include the cinder from the reduction of the pot dross, calcined dross, and litharge. They are smelted in the blast furnace, with about twice their weight of common slag ; no other fluxes are necessary. The coke employed as fuel, together with the carbonaceous matters contained in the cinder, effects its complete reduction. None but the usual precau- tions are necessary in smelting this cinder. Particular attention must, however, be paid to the charging, and to the proportion of slag added, otherwise there will be great risk of choking the furnace. The quantity of cinder smelted per annum, with results, is as follows :— Cinder smelted. Lead. Slag employed. Coke consumed. Lead produced. Tons. Per cent. Tous. Tons. Tons. 119°340 38°9 240°000 19°980 46°440 or 85°26 per cent. of total lead contained in stuff smelted. The above quantity was smelted in twenty days, and cost for CBE Vosiy. a y00 Asie Gp debe paua Chg Ree oer Smelter’s wages. 4) 25504 (eee Cartage). 6.53 oes alsa 2 ae F. 1,577°80 or per ton of cinder— Coke, 16°7 percent... «) 40 > 205 en ee WYO ein Son dacs heat, ee ee Cartage ee OR a Oe 13°20 == 10s 0G ed, Cost on ton of ore smelted, 0°45f. = 4°3d. d.— Treatment of Lead Fume.—Roasting—Owing to the peculiar nature of the fumes collected in the flues at the Pontgibaud works, it has been found impossible to smelt them advantageously alone, as is done in various other establishments. Several methods have been tried and abandoned, but the best hitherto devised, and that which is now adopted, is to mix with the fume a certain proportion of silicious ore, and fuse them together in a common roasting furnace. The fused mass thus obtained, has the appearance of a clean black slag, and closely resembles ordinary roasted ore. It is subsequently smelted in the blast furnace in precisely the same manner as already described when treating of the smelting of ores, SMELTING—PONTGIBAUD. 493 The fume and ore are intimately mixed in the following proportions before being introduced into the furnace :— Fume 60 parts, assay 62°7 per cent. lead. Ce eee pe 40-0 100 99 ? This mixture is divided into charges of 24 tons each, and treated in exactly the same way as ore which has been roasted dead. It is charged @ la pelle through the working doors of the furnace, upon the middle bed, where it is left undisturbed until the preceding charge has been melted and run out from the agglomerating bed. The charge on the middle bed is then immediately advanced towards the fire and piled up near the bridge; care being taken to move the mixture of ore and fume as gently as possible, otherwise con- siderable loss may occur from the fine particles being carried away by the draught. The whole of this charge having been advanced, and a new one introduced through the doors of the middle bed as before, the fire is urged so as to melt the mixture as quickly as possible, which is accomplished in from two to three hours. Five charges, or 123 tons, can thus be passed in one furnace in twenty- four hours, the loss of weight in roasting being about 15 per cent. The same number of men are employed as in roasting ore, but, instead of being paid by the day, they receive one franc each per charge. The consumption of coal is 17 per cent., and of lime 3 per cent. of the weight of stuff roasted. The cost of roasting one ton of a mixture of fume and ore is as follows :— Preparation of mixture . 2. . . - 1 + + O°25f. Cosi lVOkilossateibt iyi ear 2) ey sip eee 26°96 Tei at te oe cal as Salk Pan fet, sla 70 Meats tn i te a ee a re ek LoD eign Tc acu Aa enema alla Nae hea aceite Od 8 F. 9:20 = 7s. 4°3d. Cost of roasting fume on ton of ore, 0°40f. = 3°8d. Smelting.—The roasted stuff is broken and made into lits de fusion in much the same way as ordinary ore, but the proportion of fluxes added is much greater than usual. AQ4 SILVER. The lits de fusion for fume and ore are composed as follow :— UCLEN OUST BoP ae ae tr orem RE) 10,000 kilos. dO ernst sinha arspaeifor Sin eg Yarn ion ie ea a EOS i PIQGESS POE ss. ey) Deters 8s hp Bo 300 243 15,000 kilos. The above quantity is usually smelted in twenty-four hours, with a consumption of 9 per cent. of coke. The following are the costs of smelting one ton of the mixture of fume and ore in the blast furnace :— Preparation of lits de fusion. . . . . . . O-40f, Iron 120kilos: ab O5f/-°.:.) Se Limestone 350. 4, at: 208°. -. 3. 30 ye Fluor spar , 30..;,, at 16io sw a ee Coke 90° 5, BU ASE. Labour. 2 oye, Oost ee F. 25°59 = 20s. 5°6d, Cost per ton of unroasted mixture, 21°77f. = 17s. 49d. Cost of smelting fume on ton of ore, 0°95f, = 9°1d. The quantity of fume collected annually in the flues is about 154:900 tons, averaging 56°8 per cent. lead and 132 grammes, or 402. 5 dwt. silver per ton. The richness of the fume varies considerably in different parts of the flue, but in general the percentage of lead increases, whilst the proportion of silver diminishes, with the distance from the furnaces. The lead obtained from fume by the process described, amounts to 78°57 per cent. of the quantity found by assay, or 3°67 per cent. of the total weight contained in the ores treated. When it is considered how large a proportion of lead is lost by volatilisation in the form of fume by every known method of smelting lead ores, it evidently becomes a matter of importance to condense as large a proportion as possible of the metal thus driven off in order to reduce this loss to a minimum. Particular attention is now being devoted to this subject at Pontgibaud, and considerable improvements have been introduced with a view of recovering a larger proportion of fume than has been hitherto found possible. Losses of Lead and Silver.—From 100 parts of lead contained in the ores treated, 85°75 are obtained either directly from them, or indirectly from slags or fumes, viz. :— SMELTING—PONTGIBAUD. 495 — Direct from ores. . . . .. . . « , 80°04 per cent: Pe UINOR oes Ge oe et re ROT, | 4 Pee AOS acetone jk | | OA, Thine S75 e In desilverising the lead thus obtained, a loss of 3°25 per cent. is experienced, the total weight of poor lead produced for sale being 82°50 per cent. of the quantity contained in the ores. The loss in desilverising is distributed as follows :— Permittee oR ee egisg i,” 2 1°25 per cent. Improving and reducing . .. . . 2:00 99 Total Cae wad kh or 9 The loss of lead in the three principal divisions of the Pontgibaud process is therefore— Seine 74. ye... 4 Ban QO per cent. SEBO cee aes 1 ou, eee LI ECeCUVRIIth cies. 2. FFE SD Voth sae Fh7250 The percentage losses on the total quantity of silver contained in the ores are *— SAO Ree eine ih st cat . 2s ec POS per. cent: PUIATEPE LOA, eros 0d ire «O'R ” Pitalea sae. we 710) The process now employed for the extraction of the silver is not only much superior to the old Pontgibaud method, but is even more perfect than the best methods of assaying at present known, since, in the large way, from 34 to 4 per cent. more silver is obtained than the assays indicate. Of 100 parts of silver produced— 98°82 are obtained direct from the ores. 0°64 ,, ,, from the slags. OD4. =. “ - fumes. 100°00 * These losses are indicated by the assay of the slags and market lead, since the amount of silver annually obtained is, nevertheless, considerably in excess of the weight determined by assay. 496 SILVER. The quantities of lead and silver sold from the Pontgibaud Smelt- ing Works for the years ending June, 1865, and June, 1866, were as follow : — 1865 Lead _1,391 tons Silver 124,230 oz. : 1866> Lead 1,550 tons Silver 145,280 oz. rgb Value. , . « tL hee 69,420 Summary of Costs. Cost per Ton of Ore Cost per Ton of Lead produced. smelted. PSG". 3s se ee af: Preparation of “ Lits de Grillage”| 0°25 Roasting Ore . . . . . . . /19°75 ois ay 4 9 Matt 1:05 » Fume 0°40 Preparation of “ Lits de Fusion” 0°25 Smelting Ore . . .. . . . (21-06 22°71 = 018) a0 - POOF Pye DOM 6x08 re Lead Cinder. . . . | 0°45 faeces Ordinary Work Lead sae B99 2-4) Vo ass Hard Lead. . .° . 1 1:08 Cryptalliging A. de ise libcc. sabe se 12°39 = 0 9 10°9 PUI SG a Se) ee So 227= 0 1 9'8 ; Pot Dross & Litharge | 1-7 Reducing { 0 icined Dross . . nat AS Sane Ameltine Blag iy. 3 AM 610= 0 4106 70°26 =£2 16 2-4 fe; Gefen ae 48°04 = 119 1:8 61°82 2 Aaa 6°69 =. 0 § 789 23°27 a= 1 Bs 518 = 0 .4-29 5°00==) 520) eA edes, 13°92 =" 0 117 16 160°32 = £6 8 2-9 Cost per Kilo. of Silver produced. £2 °¢: SoS 0es 16°78 = 0 13. 50 1777 = 0.14 26 2°29 = 0. 210"0 970s? DOH 177= 0 1 50 1'3s8= 0 1 60 477 = 0 39S 54°96 = 2 311°5 N.B.—General Expenses are not included in the above statement. CHAPTER XXIII. SMELTING SILVER ORES IN MEXICO. ROASTING—FUSION-—CUPELLATION—VASO—GALEME—NUFLA. In Mexico, only the richer varieties of silver ore are smelted, by far the larger proportion being treated by the patio process ; whilst in some few of the mining districts, as at Real del Monte, barrel amalgamation is extensively resorted to. Roasting.—The ores destined for smelting are, at Zacatecas, and in some other localities, subjected to a process of roasting in heaps, which is effected by surrounding the mineral, broken into large lumps, with a layer of charcoal, retained in its place by an open wall of rough stone built in a circular form. The openings in this wall admit of the passage of the necessary amount of air, and the operation is completed in the course of twenty-four hours, with an expenditure of charcoal amounting to one-half the weight of the ores operated on. At Nieves the ores are roasted in circular kilns four feet six inches in diameter, and of about the same height. These are formed of a hollow wall of adobes or sun-dried bricks, and are without a roof, the walls being so constructed that the area of the openings is nearly equal to that of the brickwork between them. Into each of these kilns are charged 2,000 Ibs. of roughly-broken ore, intermixed with one-half its weight of dry wood; the operation requires a week for its completion; but this method of roasting can only be employed during the dry season. Fusion.—The fusion of the roasted ore is effected in a small blast furnace, having the following dimensions: height to the charging hole 4 feet 6 inches, and depth from the front to the back wall 15 inches, width at top 11 inches, and at bottom only about 9 inches. The aperture through which the fused materials make their escape is about 24 inches in diameter, and is situated at the bottom of the furnace, whilst the copper nozzle through which the blast is supplied is placed about 9 inches above it. The breast, which is built of fire- KK 498 SILVER. stone, is taken down whenever the furnace becomes choked, or when — it is found necessary to re-line the interior with a fresh coating of re- fractory clay ; which is usually required at the expiration of a week from the time of first getting the apparatus into blast. In front of the furnace, and below the aperture through which the various fused matters make their escape, is a breast pan 10 x 13 inches, in which they accumulate, and from which the lead and other fused matters are from time to time tapped into a basin, situated at a still lower level; whilst the slags are removed from the breast pan when- ever any portion of them becomes sufficiently solid. The blast 1s supplied by bellows, set in motion by cams, fixed in a horizontal axle connected, by toothed gearing, with a vertical shaft, to which a mule is attached. A couple of these furnaces are usually built side by side under a hood of masonry, open at the top for the escape of metallic fumes and the products of combustion. In front of each, is a series of bins containing the ores to be smelted, which are mixed in various proportions with the different fluxes employed. The fuel made use of is, in most instances, charcoal, pre- pared either from pine or green oak. This furnace, which was first introduced into the country by the - Spaniards, and appears to have undergone but little modification during the last three centuries, is that still almost universally employed in the different native establishments, although furnaces on the model of those used in the metallurgical works of the continent of Europe have replaced them in the larger haciendas, conducted under the superintendence of Europeans. The materials employed as fluxes, or for the purpose of supplying the lead necessary for the extraction of silver, are tequezquite, or native carbonate of soda, collected during the dry season from the beds of certain lagunes ; greta, or litharge, frequently very impure, and chiefly derived from the treatment of the lead ores of Mazapil and Zimapan; temesquitate, or the slags which float on the Jead bath of the furnace known as the “fhufla,” in which silver is extracted by a process of scorification ; crasas, or the slags obtained during the progress of previous operations; and jierros, or the impure litharge, which floats on the surface of the lead bath during the earlier stages of the process of cupellation in the test furnace with a movable dome: this name is also applied to the matts obtained during the operation of smelting, which, together with cupel bottoms, and cther materials containing lead, are added to the charge during succeeding operations. SMELTING—MEXICO. 499 - The ore, after having been previously roasted, is placed in hutches before the furnaces, from which it is taken to be mixed with the various fluxes and furnace products constituting a charge. At Sombrerete, where the rich ores are chiefly composed of quartz, iron pyrites, and the sulphides of silver, the furnace mixture was, in 1842, according to Duport, constituted as follows :— are eres ce at an 2, 375 1 DE: Tequezquite . ere Temesquitate Soha ee eee ee ear pees Spel outrage tN Se gets grit. Byerly Fierros . Moroes oe hae he dicions gt Le es STE Pigs Nae Oa YE ee eater aes chat The fusion of these ingredients produced a pig of lead weighing from fifty to fifty-eight pounds. The ores from La Cafiada, which contain a larger proportion of lead, required a less amount of litharge, and somewhat less of the native carbonate of soda. The campaign of a blast furnace begins on the Sunday evening, and extends to the morning of the following Sunday, at the expira- tion of which time the bad quality of the materials employed renders it necessary to suspend operations for the purpose of making repairs. After getting the apparatus into blast, 300 lbs. of lead ore are first passed through it, and of which the yield of metal is not calculated in the results obtained. As soon as the preliminary charge has been fused, the mixture of ore and fluxes is thrown into the furnace, with alternate charges of charcoal, as often as its contents descend suffi- ciently below the level of the charging hole. The smelter, who has charge of two furnaces, takes care to keep the eye constantly open, and for this purpose frequently introduces an iron bar, with which he gently raises the slags and fuel which occupy the lower portion of the apparatus; he also attends to the proper regulation of the blast, and the proportion of fuel to be employed. When a sufficient amount of lead to form an ingot has accumulated in the breast pan, the blast is stopped, and the eye of the furnace is closed by a plug of clay ; after which the dam, between the breast and receiving basins, is pierced, and the fused metal and matt are allowed to flow into the latter, when the eye of the furnace is again opened, and the operation continued until enough lead to yield another ingot has been produced. As soon as the contents of the tapping pan have become sufficiently cooled, the matts are removed from the surface of the bath of lead, K K 2 500 SILVER. and at once passed through the furnace with the next charge, after which the metallic lead is ladled into a convenient mould. The foreman is assisted during this work by a man who charges the two. furnaces, and by another who attends to the preparation of the mix- ture of ore and fluxes ; he is relieved every twelve hours by another smelter and his assistants. The quantity of charcoal consumed during the production of an ingot of metal varies from fifty to seventy-five pounds ; and from eight to twelve are produced in the course of twenty-four hours, according to the nature and richness of the ore treated. When the minerals operated on contain a considerable amount of lead, each furnace will sometimes smelt as much as a ton of roasted ore in the course of twenty four hours, with a consumption of about 55 per cent. of char- coal; but such results can only be obtained under very favourable cir- cumstances. Cupellation—The furnace usually employed for cupelling the argentiferous lead, resulting from the foregoing operation of smelt- ing, is called a Vaso, and differs but slightly in its construction from many of those used for the same purpose on the continent of Europe. The hearth of the vaso is not, however, renewed after each working, but is employed for the cupellation of successive parcels of lead, until the test which, when new, is three feet in thickness, has become worn through. The bottom of the furnace, or cendrada, is composed of three parts of wood-ash and one of clay, well mixed together, and carefully beaten in. In the largest description of cupelling furnace, the greatest diameter of the cendrada is 4 feet 6 inches, and of the smaller one, 4 feet ; whilst the depth of the cavity for the reception of the metal is about 5 inches. The fireplace varies in its dimensions according to the nature of the fuel employed; requiring to be larger where the wood of the palm tree is made use of, than for furnaces in which pine is alone consumed. It is, however, in all cases situated very close to the edge of the cupel; but as this has itself a considerable diameter, it follows that towards the close of the operation the metal is at so ereat a distance from the fuel that the heat produced is far from being economically applied. The blast is furnished by bellows worked by two men, who relieve each other alternately ; the bellows communicating with a movable tuyere capable of being depressed, in proportion as the bottom of the cupel itself becomes lowered. The blast thus apphed drives before it the oxide of lead towards an SMELTING—-MEXICO. 5OL opening in the opposite side of the hearth, and of which the level is lowered, in proportion as the depth of the metallic bath becomes less, These furnaces are not provided with chimneys, the products of combustion making their escape by a long low opening, situated opposite the fireplace, and on a level with the edge of the hearth, which also serves for the introduction of the ingots of metal to be eupelled. In order to prevent injury to the workmen from the action of volatilised oxide of lead, these furnaces, like those employed for smelting ores, are placed under large hoods of masonry, which effec- tually carry off the smoke and metallic vapours, so that the refiners are but little subject to’diseases incidental to exposure to lead fumes. Although this apparatus is that still most commonly employed by Mexicans for the cupellation of argentiferous lead, the larger establish- ments now make use of the ordinary cupelling furnace fitted with a movable iron dome. The planchas or ingots of argentiferous lead are taken from the smelting furnace to the vaso, which is capable of working off about two thousand pounds of lead in the course of twenty-four hours. The working of this furnace is conducted by a refiner and two workmen, who attend to the bellows, and are relieved every twelve hours by another foreman, and his two assistants who supply the blast. The fuel employed is usually pine wood split into small pieces, of which some six or eight hundred pounds weight are consumed in the course of twenty-four hours. In this furnace the process of refining is not generally carried so far as to allow the silver to brighten, but as soon as the metal remaining in the cupel begins to assume an iridescent appearance, the last is arrested, and the fire withdrawn. The silver obtained by these means is, in the majority of cases, the property of individuals who sell it without its being assayed, and whose interest, consequently, is not to remove the whole of the lead; the resulting plates, therefore, usually contain from 970 to 985 thousandths of silver. In addition to lead, the silver obtained by this process generally contains a small amount of anti- mony, and requires to be refined, with an addition of pure lead, before it becomes sufficiently soft to admit of its conversion into coin. The cost of smelting ores in Mexico is in all cases exceed- ingly high, but varies considerably in’ accordance with the nature of the power employed for supplying the blast. When, as is usually the case, mules are made use of for working the bellows, the expenses for power and manual labour are excessive, and at Zacatecas the 502 SILVER. costs under this head alone amounted, in 1842, to no less than $36. per ton, including the wages of the men employed for the cupel- lation of the resulting argentiferous lead: charcoal generally costs about 24 reals per arroba of 251bs., and these several expenses, added to the value of the litharge lost during each operation, made the total cost, at Zacatecas, of treating a ton of ore by this system, about $133, or 26/. 12s. per ton. The high price of smelting ores in Mexico is not, however, the only objection to the more general appli- cation of this process, since the loss of silver by the imperfect pro- cesses employed appears in all cases to be very considerable ; varying, according to the nature of the ores and the skill of the workmen employed, from 15 to 25 per cent. on the assay value. The quantity of ore daily smelted at Zacatecas was estimated by Duport, in 1842, at from five to six tons only. At Sombrerete, where the ores are generally rich, and where a larger proportion of them is, consequently, treated by smelting, the cost did not generally exceed about 13/. per ton; whilst at Nieves, which is at a more convenient distance from Mazapil, from whence the chief supply of litharge is obtained, and where the ores themselves contain a considerable amount of lead, the total expense of smelting a ton of mineral, together with that of refining the resulting work lead, was estimated at 6/. 6s. In some districts, in which water power is unusually abundant, the treatment of the ores is effected at an even less cost than the above; but such cases must, nevertheless, be regarded as altogether exceptional. The amount of silver obtained in Mexico by smelting, as compared with the total produce of the country, was estimated, in 1842, as being about one-tenth, but is now much less. Galeme.—In some localities, a smaller, and more rudely-constructed apparatus than the vaso is employed for the cupellation of work lead obtained from the blast furnace. This arrangement, called a galeme, is constructed by marking out on a floor of well-beaten clay a space 2 feet 3 inches long, and 1 foot 8 inches wide, which is enclosed by a wall of stone, about 6 inches high, supporting a stone slab, or a large brick, forming the top, and covering the whole space. At one end is placed the fuel, consisting of pine wood, cut into small fragments, on which a current of air (supplied by bellows, worked by a lever) is directed, by means of an iron nozzle; whilst sundry small apertures at the other extremity allow of the escape of the products of combus- tion. Before charging the furnace, it is heated for some hours, in order to raise the temperature of the masonry to the proper point, and to so SMELTING—MEXICO. 503 vitrify the hearth as to render it, to a great extent, impervious to litharge. An ingot of lead, weighing from forty to fifty pounds, is now introduced, and an aperture left in the side is partially stopped with clay, so as to allow the litharge to flow off; care being taken to lower its level in proportion as the surface of the metallic bath be- comes depressed. The lead, thus placed in close proximity to the burning fuel, becomes rapidly converted into litharge, and the cupel- lation proceeds at the rate of about an ingot per hour, although the loss of that metal is considerable, and a deficit on the silver is the result. The galeme is the only means of cupellation employed in the mining district of Charcas, and is also made use of at Catorce, for refining the impure silver obtained by the treatment of silver ores in the cazo, The Nufla.—This furnace is probably the most primitive apparatus employed in any country for the extraction, by the dry way, of silver from its ores; and is in principle merely a scorifier, in which the cupellation of the remaining lead is subsequently effected. The sulphides of silver sometimes occur in so large a proportion, with regard to the gangue with which they are associated, that if finely ground and thrown on a bath of metallic lead kept at a proper temperature, the silver combines with the lead; which, becoming partially oxidised, unites with the silicious and earthy impurities of the gangue, forming a slag, which may be readily removed from the surface of the metal before commencing the operation of cupel- lation. This apparatus, which is much employed by the native miners of Sombrerete, consists of a cupel formed of a mixture of ashes and clay, contained in a large coarse earthen dish; enclosed between walls of sun-dried bricks, and covered by a dome of some- what refractory clay, in which numerous holes are pierced. The whole of the interior of this arrangement is filled with charcoal, on which a blast is thrown by means of a nozzle of baked clay; and, although the whole of the heat is applied from above the surface of the lead, it quickly melts, and the scorification of the ore, thrown on its surface, commences. When the workman considers that the bath of lead has, by the introduction of successive additions of ore, become sufficiently charged with silver, he cleans off the silicious slags, and commences the cupellation of the residual lead. For this purpose he makes an opening at the level of the metallic bath for the escape of litharge, and continues the operation, at the same time gradually lowering the level of the exit for litharge, until a button of silver alone remains in the bottom of the cupel. CHAPTER XXIV. ASSAY OF SILVER ORES AND BULLION. ARGENTIFEROUS GALENA-—ASSAY OF SILVER ORES PROPER—SCORIFICATION— CUPELLATION—ASSAY TABLE—-ASSAY OF SILVER BULLION. ASSAY OF SILvER OrES.—In the assay of ores of this metal, the object sought is first to obtain the silver present in the mineral in the — form of an alloy with lead, which is subsequently passed to the muffle and cupelled, with proper precautions. Argentiferous Galena.—The assay of argentiferous galena is, in this country, usually conducted in a wrought iron crucible. The vessel employed for this purpose is made of a piece of plate iron, of good quality, turned up in the form of a crucible, and carefully welded at the edges; the bottom is closed by a large iron rivet, securely welded to the sides, and the whole finished. by the hammer on a properly- formed mould. To make an assay in a crucible of this description, it is first placed in the assay furnace, and heated to dull redness; and when it has become sufficiently hot, 400 grains of the pulverised ore, intimately mixed with its own weight of soda-ash, about 30 grains of pearlash, and from 8 to 10 grains of charcoal powder, or lamp-black, are introduced by means of a long copper scoop. With certain varieties of ore, the addition of a small quantity of common salt, or fluor spar, is found to be beneficial for the production of a thoroughly liquid slag ; fluor spar being particularly advantageous in the case of highly silicious ores. On the top of this, is placed a thin layer of dried borax; and the crucible, which, for the introduction of the mix- ture, has been withdrawn from the fire, is at once replaced in the furnace. At first the contents of the pot boil somewhat violently, and therefore, in order to avoid loss, the crucible should be made of sufficient capacity to prevent any portion of the mixture being pro- jected over its sides. At the expiration of from eight to ten minutes, the ingredients in the crucible will be observed to be in a state of tranquil fusion ; and the pot must now be removed from the fire, and its contents briskly stirred by means of a small iron rod, flattened at ASSAY OF SILVER ORES. 505 the end in the form of a spatula. Any matters adhering to its sides are also scraped downward into the bottom of the pot, which is replaced in the furnace, and, after being closed with an earthen cover, is, during three or four minutes, heated to full redness. The crucible is now seized, by a strong pair of bent tongs, on that “part of its edge which is opposite to the lip; and, after being removed from the fire, its contents are rapidly poured into a cast iron mould, having internally the form of an ordinary egg cup. The sides of the pot are now carefully scraped down with the chisel-edged bar before referred to, and any adhering particles of lead and slag are obtained by sharply striking the edge of the crucible against the top of another east iron mould, similar to that into which the assay was first poured. When sufficiently cold, the contents of the mould are readily removed by merely turning it over; and the metallic button, after being separated from the adhering slag, is carefully cleaned by means of a hard brush, and weighed, in order to determine the percentage yield of lead. When a metallic shot has been obtained in the second mould, it must be freed from adhering slag, and weighed with the larger button. The alloy thus obtained is cupelled, in order to determine the amount of silver which it contains. Assay of Silver Ores Proper—Ores of silver, in which that metal exists in the form either of oxide, sulphide, or chloride, in a gangue principally consisting of silica or of carbonate of lime, are usually fused with a mixture of litharge and carbonate of soda, to which a smail quantity of finely-powdered charcoal is added; and by this means: a button of alloy is obtained, which is subsequently treated by cupellation. — The proportion of litharge to be employed for this operation must be varied in accordance with the circumstances of the case, as the resulting button of alloy should not be too rich in silver, since, in that case, a portion might be lost in the slags; neither should it, on the other hand, be too poor, as the cupellation would then occupy a long time, and a loss through absorption be the result. In ordinary cases, where the silver principally exists in the form of chloride and sulphide, and the quantity operated on is 400 grains, a button of alloy weighing about 200 grains will be a convenient amount for cupella- tion: such a result may generally be obtained by the addition of 300 grains of litharge, 400 grains of carbonate of soda, 150 grains of borax, and from 7 to 8 grains of finely-powdered charcoal. The whole is to be well mixed, and introduced into an earthen crucible, of 506 SILVER. which it should not occupy more than one-half the capacity. Ordinary French pots are best adapted for making all assays in which large quantities of litharge are made use of, as they resist its action better than any of the pots usually.made in this country. The crucible is now placed in an assay furnace of the usual form, care being taken to withdraw it from the fire as soon as a thoroughly liquid and perfectly homogeneous slag has been attained; since the fused mixture would otherwise be liable to cut through the sides of the pot, and thus spoil the experiment. When it has sufficiently cooled, the crucible is broken and the metallic button obtained, which, after being properly cleaned, is passed to the cupel. When a great degree of accuracy is required, it is always best to break the pot, and extract the button of alloy, as above described; but when numerous assays have to be made on ores of nearly the same tenure, the assay is sometimes poured into an iron mould, and the crucible is employed for making other fusions. In this, and all similar cases, it is, of course, essential to ascertain, by previous experiment, the proportion of silver contained in the lead obtained by the reduction of the litharge, in order to obtain the necessary data for calculating the requisite deduction to be made from the results afforded by cupellation. When, however, very poor litharge is made use of, the resulting lead contains so small an amount of silver that, for some commercial pur- poses, its presence may be disregarded: generally speaking, however, the assayer, on the receipt of a fresh supply of that reagent, ascer- tains, by means of careful assays, the proportion of silver which it contains, and makes the necessary correction on each assay in which it is employed. Argentiferous minerals containing a considerable amount of copper may be generally assayed by this process, since the amount of that metal which enters into combination with the lead produced is com- paratively small, and the resulting button of alloy admits of being readily cupelled by the addition, when necessary, of metallic lead. When the mineral to be assayed contains a large proportion of metallic sulphides, the addition of charcoal, or any other reducing agent, becomes unnecessary, as litharge readily attacks all the simple and complex metallic sulphides, oxidising their constituents, with the exception of the precious metals, which form an alloy with the lead set free. The slags resulting from this operation contain the excess of litharge added, and the button of alloy produced is subjected to cupellation. The proportion of oxide of lead to be added to ores of Mee Se ASSAY OF SILVER ORES. - 507 this description varies in accordance with their composition, but it should in all cases be present in decided excess, since, should the sulphides not become completely decomposed, the whole of the silver will not be concentrated in the resulting button of alloy. For the successful assay of pure argentiferous iron pyrites, as many as 50 parts of litharge are required, whilst for mispickel, blende, copper pyrites, grey cobalt, and sulphide of antimony, from 15 to 20 times their weight may be employed.* It must, however, be remembered that earthy and silicious gangues usually constitute a large proportion of the bulk of the ores operated on, and consequently these excessive amounts of litharge are, in practice, seldom requisite. One of the chief objections to this method of assay is the large amounts of lead that are produced for cupellation, since pure iron pyrites affords 8:50 parts of this metal, whilst sulphide of antimony, and grey copper ore, yield from six to seven parts. This inconvenience may be obviated by effecting the partial oxida- tion of the sulphides, either by roasting or through the aid of nitre, by the skilful use of which a button of almost any required weight may be obtained. If this reagent be employed in excess it deter- mines the oxidation of the various metallic and other oxidisable sub- stances present, not always excepting silver itself. When, however, the mixture at the same time contains an excess of litharge, and nitre has not been added in sufficient quantity to effect the decomposition of the whole of the sulphides present, reaction takes place between the portion of sulphide undecomposed and the oxide of lead added. This gives rise to the formation of a button of metallic lead, which, combining with the silver, affords a button of alloy suitable for cupellation. The amount of nitre required to be employed for this purpose necessarily depends on the nature and richness of the ore operated on, but it must be borne in mind that 2°5 parts of nitrate of potash are sufficient to completely oxidise the constituents of iron pyrites, and that 1:5 and 0:70 parts, respectively, are, in the case of sulphide of antimony and galena, sufficient for this purpose. When the ores contain a large proportion of sulphides, it is gene- rally found most desirable to conduct the assay on the mineral after calcination. The roasting of the pulverised ore is best effected in a shallow scorifier, or earthen dish, into which a weighed quantity of the mineral to be operated on, (generally 400 grains) is introduced, and then carefully roasted in the muffle of a cupelling furnace. For this * Berthier, Traité des Essais par la Voie Séche, tome il. p. 827. 508 SILVER. purpose the scorifier and its contents should be first placed in the mouth of the muffle, and kept constantly stirred with a thin bent iron rod ; care being taken to commence the operation at a low temperature, since, from their great fusibility, such ores would be otherwise liable to agelutinate. As the calcination progresses, the scorifier may be gradually pushed further into the muffle, and thus subjected to successively in- creasing temperatures ; as soon as sulphurous vapours are no longer evolved at a full red heat, the scorifier and its contents are withdrawn. and allowed to cool. The ore, when sufficiently cold, is carefully removed from the earthen dish, and mixed, on a sheet of glazed paper, with the fluxes requisite for effecting its fusion, and the reduction of the quantity of lead necessary for cupellation. When the amount of mineral operated on is 400 grains, there should be added soda-ash 400 grains, borax 200 grains, litharge 400 grains, and charcoal 10 to 12 grains. The whole is now introduced into an earthen crucible, fused with the usual precautions, and the resulting button of lead passed to the cupel. | Scorification—This is a simple and convenient method of assaying ores containing the precious metals, when large quantities of metallic sulphides are present. The process consists in subjecting the finely- pulverised minerals, mixed with granulated lead and placed in a saucer- shaped earthen vessel or scorifier, to the action of a bright red heat in an ordinary assay muffle. A portion of the lead is thus converted into litharge, which, as fast as itis produced, combines with the various silicious and earthy constituents of the veinstone, forming slags, in which the other metallic oxides produced are taken up, whilst the silver and gold form an alloy with the lead remaining at the close of the operation. The scorifiers employed for this purpose should be made of well-baked close-grained fire-clay. It is necessary that they should be compact in their structure in order to resist the corrosive action of the litharge, and that they should be capable of withstanding sudden changes of temperature without breaking. A number of these scorifiers corresponding to that of the assays to be made are selected, and into each are introduced 100 grains of powdered raw ore, intimately mixed with from five to eight times its weight of granulated lead, and a small quantity of dried borax. In all cases, however, the lead should be added in excess, as the resulting slags are thereby rendered more liquid. The granulated lead used for this purpose should, if possible, be almost entirely free from silver, but this is difficult to obtain, and when it cannot be ASSAY. OF SILVER ORES. DOO procured it becomes necessary to estimate beforehand the amount of silver contained in the lead employed, and to make a corresponding deduction from the weight of the button afforded by cupellation. The scorifiers, after being duly charged with the ore, lead, and borax, are taken to the furnace and introduced into the muffle, which has been previously brought to a full red heat. . Their introduction at first considerably reduces the temperature of the furnace, and some pieces of charcoal should be placed in the opening of the muffle for the purpose of again raising the heat to the proper point. The muffle door is now closed, and in the course of a few minutes the lead enters into fusion, whilst white vapours are -observed to rise from the assay, and the formation of litharge rapidly takes place. In proportion as the borax fuses, and the quantity of htharge increases, the contents of the scorifier soften; and as the temperature becomes more elevated, they enter into fusion, whilst the lead accumulates in the centre, in the form of a large metallic globule. When the assays have reached a bright red heat, which is usually the case in from ten to fifteen minutes from the commencement of the operation, the stopper of the muffle 1s removed ; and the current of air, which now enters, causes the oxidation of the lead to proceed more rapidly. In proportion as the ltharge accumulates, the slag formed, by its combination with the earthy, silicious, and other matters contained in the ores, increases in quantity, and gradually extends itself over the whole surface of the lead. The door of the muffle is allowed to remain open about fifteen minutes, at the expira- tion of which time it is again closed, and the temperature is raised for about five minutes to full redness, for the double purpose of rendering the scorie as liquid as possible previously to pouring, and also to facilitate at the same time the reunion of any disseminated elobules of metallic lead. The scorifiers are now withdrawn by means of proper tongs, and their contents rapidly poured into moulds. When sufficiently cold, the buttons of lead are detached from the adhering slags by being hammered on a small anvil, and are then passed to the cupel. When this operation has been successfully conducted, the resulting buttons of alloy contain, practically, the whole of the precious metals present in the ore. It is, however, essential that the slags should be perfectly and uniformly liquid at the time of being poured into the moulds, for should they either be pasty or contain imperfectly fused lumps, a portion of the mineral will remain unacted on, and small metallic DLO 5. SILVER. buttons may either be enclosed in the unfused part, or remain attached to the scorifier. 1 When, in spite of the temperature of the muffle and the other conditions of the process having been carefully attended to, the slags do not become sufficiently liquid, it is necessary to introduce an additional quantity of borax, and in some cases a little nitre may be added with advantage. Sometimes, although rarely, it is found necessary to stir the slags with an iron rod, for the purpose of dividing any lumps that may have been formed, and to incorporate them with the more liquid scorie. This method of assay is applicable to all kinds of argentiferous and auriferous minerals, of moderate richness, containing large amounts of metallic sulphides; and, from its convenience and freedom from causes of error, it is very generally employed in establishments in which such ores are subjected to metallurgical treatment. When, however, very poor ores have to be operated on, the ordinary method of fusion with litharge is to be preferred, since larger quantities can thus be dealt with, and more accurate results consequently obtained. Cupellation.—The cupellation of the buttons of argentiferous lead is conducted as described when treating of the assay of auriferous compounds, but as silver is, at high temperatures, more volatile than gold, the heat requires to be more carefully regulated than is neces- sary in the case of gold ores. In making all cupellations it is neces- sary to bear in mind that a cupel is only capable of absorbing about its own weight of litharge, and consequently a test should always be employed a little heavier than the button of alloy to be subjected to the operation. The results obtained are also, to a certain extent, influenced by the temperature at which the cupellation has been conducted, and eon- sequently all assays are liable toa small amount of error. If the muffle be too strongly heated, the silver becomes perfectly refined, but experiences a small amount of loss, through sublimation and the absorption of the cupel; whilst, on the contrary, when the tempera- ture has not been sufficiently elevated, the button is liable to retain -a small portion of lead. These two causes of error, existing at the same time in all cupellations, are found, in practice, to often nearly neutralise each other; although, in order to obtain uniform results from the same alloy, it is necessary to employ various minute precau- tions, both with regard to the temperature of the muffle and the con- dition of the cupels employed. The more important of these pre- ASSAY OF SILVER ORES. 511 cautions have been specified when treating of the assay of gold ores, and will be found in detail in all works on the assay of minerals by the dry way, but a small amount of practical experience will be far more advantagevus than any mere verbal instructions. When, however, the amount of lead employed has been sufficient, the cupel is perfectly dry, is made of fine and well-prepared Lone-ash, and the cupellation is conducted at a full cherry-red heat, the results obtained will, in almost,_all cases, be found of a satisfactory character. If the resulting buttons of silver be large they should not be abruptly withdrawn from the muffle, but be gradually drawn towards its mouth, since their sudden removal ‘might cause them to “spirt,’ and a loss be thereby entailed. In the case of a very large button being obtained it is sometimes found advantageous to cover it, immediately after brightening, andbefore its removal from the muffle, by another cupel kept hot for that purpose. When it has sufficiently cooled the metallic button is seized, laterally, between the jaws of a pair of strong pliers, and tightly squeezed, for the double purpose of loosening it from the cupel and detaching any adhering litharge. The button is then cleaned by the did of a stiff brush, and weighed in a delicate assay balance. When, in addition to silver, the mineral under examination contains gold, the button obtained on the cupel is first weighed, and its weight noted; it is then flattened, dissolved in nitric acid, and the gold also weighed ; the difference of the two weights thus obtained corresponds to the amount of silver present in the assay. The weight of mineral employed for making an assay is, to a great extent, regulated by the amount of silver which the ores are supposed to contain, In Cornwall, for assays of argentiferous galena, the quantity operated on is often one ounce avoirdupois. In the mining districts of Nevada, two hundred grains are commonly made use of, and the contents of the crucible are often poured out into an iron mould. Scorifications are not easily conducted, in the common mufile furnace, on much above one hundred grains; but for assays of an ordinary silver ore by fusion, four hundred grains are conveniently employed. For commercial purposes, the silver contained in any given mineral is, in this country, estimated in oz. dwt. and gr., one ton of 2,240 lbs. avoirdupois being taken as the standard of unity. 512 SILVER. TABLE showing the weight of Silver to the ton of Ore corresponding to the weight in grains and decimal parts of a grain, obtained from 400 grains of Mineral.” pee segue ne | One ton of Ore will | Pade ee One ton of Ore will Fine Metal, oe Fine Metal, vie cag, oz. dwt. gr. gr. oz. dwt. gr. 0-001 0 115 0:200 16 616 0-002 3.6 0°300 2410 0 0-003 0 4 21 0°400 3213 8 0:004 0 612 0500 40 16 16 01008 2). 30-8 ao O6n0 49 0 0: : 01006 1, 0-919 0700 57. gas 0007 0 11 10 (800 65 6 16 0-008 OAc Tt 0900 7310 0 - 0-009 0 14 16 1-000 8113 8 0-010 016 8 2-000 163 6 16 0020 1 12 16 3-000 245 0 0 0030 28920 4:000 326 13 8 0:040 3 8 5*000 408 6 16 0050 4 116 6-000 490 0 0 0060 418 0 7:000 B71 de.c8 *, 0-070 514 8 8000 653 6 16 : 0-080 6 10 16 9-000 735 0 0 0-090 7 6: el BO DOR 816 13. 8 0100 Baas 20°000 1633 6 16 ASSAY OF SILVER BuLLION.—The assay, by the dry way, of silver bullion comprehends three distinct operations. First, the accurate weighing of a given quantity of the alloy to be operated on ; secondly, the cupellation, with due precautions, of this weighed portion with a proper amount of metallic lead; and, thirdly, the re-weighing of the pure silver thus obtained, when the loss of weight will correspond to- the amount of alloy which has been removed. The furnace used for this purpose should be provided with the means of very accurately regulating the temperature ; and is therefore generally constructed of a wrought iron shell, internally lined with firebrick, and has sliding doors arranged at each of its openings, by the aid of which the several apertures can, at the pleasure of the operator, be easily con- tracted or enlarged. The quantity taken for examination is usually in this country * For the inethod of using this Table, see page 235. ASSAY OF SILVER BULLION. 513 a representative of the troy pound; which is subdivided into -ounces and half-pennyweights, that being the lowest denomination to which assays of silver bullion are reported. It is evident that the assay pound may be represented by any actual weight chosen by the assayer, but from 10 grains to 1 gramme, about 15°44 grains, is the quantity most frequently employed by English assayers. An assay pound of 10 grains, with weights corresponding to the ounces and half-pennyweight, is very convenient for silver assays. The old assayers made their calculations in ounces, pennyweights, and grains, but it is more convenient to work by the decimal system, and, when trade estimations are required, to convert the decimal into trade expressions. By this method pure silver will be called 1,000, and English standard, which contains in the pound 11 oz. 2 dwt. of silver, with 18 dwt. of alloy, will be 925 in the thousand. Assayers’ therefore often speak of such an alloy as being 925 fine, and this expression is constantly employed in the different American mints. All excess of alloy over the English standard is, in this country, called “ worse- ness,” and Mexican dollars, which are composed of a mixture of 10 oz. 16$ dwt. of silver, with 1 oz. 34 dwt. of alloy, would be reported as “worse” 54 dwt. The true decimal expression of such a mixture would be 902°7, or worse 5 dwt. 8 gr; but, as trade reports are only made to the half-pennyweight, it would be reported W. 54 dwt.* On the other hand, certain Indian rupees are composed of 950 parts of silver, united with 50 parts of alloy. This is equal to 11 oz. 8 dwt. of silver, combined with 12 dwt. of alloy, and hence their trade report would be “ better” 6 dwt. The first step to be taken in making an assay of silver bullion is to flatten out, in the form of a thin disc, the cutting taken from a bar, The edges of this are carefully cut off, and from the centre are prepared two assay pounds, which are wrapped in pieces of sheet lead, amounting to about one-half the weight necessary for effecting their cupellation, The amount of lead necessary for this purpose increases in proportion with the amount of alloy present in the specimen under examination, but even fine silver requires, according to Makins, three times its weight of that metal to ensure a satisfactory result. English standard silver will require six times its weight, and coarser varieties a proportionately larger amount. The estimation of the quantity of * Making, “ Manual of Metallurgy,” p. 172. LL 20: Cae SILVER. lead required is a matter to be determined by the experience of the assayer. It should, however, be as free as possible from silver, and the amount of that metal in the lead employed must be mein. from the results obtained. The several weighed portions of the bars of bullion to be assnyed, after being carefully wrapped in lead foil, are arranged in the compart- ments of a divided tray, having nearly the dimensions of the bottom of the muffle, so that the place of each cupel may correspond with its position in the furnace during the operation of cupeilation. During the preparation of the different assays, the heat of the furnace must be got up, and a number of cupels placed in regular order in the mufile, so that they may become heated to the proper temperature. When the muffle and cupels have attained a uniform bright red colour, and the fuel in the furnace is in a compact state and free from cavities, the muffle door is closed by pieces of charcoal. This is done by commencing with large pieces, which are followed by a layer of smaller ones, and so on, until the orifice 1s about two- thirds built up. | The remainder of the lead necessary for cupellation is now intro- duced into the cupels by means of proper tongs, and, when it has become fused, the assays, wrapped in the necessary amount of lead foil, are placed in their respective cupels. When they have been all placed in their proper positions, the assayer completes the closing of the mouth by means of small twigs of charcoal, and, shortly afterwards, removes some of the upper pieces for the purpose of admitting a current of air, by which the starting of the cupellations is effected. This makes itself apparent by the metallic bath becoming uncovered, with the exception of certain small patches of oxide of lead, which circulate from the centre towards the edges. "When the working has been thus fairly set up, the adjustment of the draught, by means of the various furnace openings, must be carefully attended to, in order to maintain a steady circulation from the centre towards the cireum- ference, where the litharge, as fast as it 1s produced, is absorbed by the bone-ash of the cupel. During this operation little or no fume should be apparent, as the whole of the lead should, as far as possible, - be converted into oxide, and absorbed by the cupel. In this way the globule of fused metal goes on diminishing in size, until finally, after the expiration of from twenty minutes to half an hour, the whole of the lead and base metals have become oxidised, and the phenomenon of brightening takes place. ASSAY OF SILVER BULLION. 515 When the Be ccin has been skilfully conducted, the “going off ” of the assays will commence with the front row, and gradually pass back, from row to row, to the last. When, on the contrary, the working off takes place irregularly, or commences at the far end of the muffle, it is an indication that the management of fire has been unskilfully conducted, and the resulting assays will turn out unsatisfactorily. It now only remains to remove the “mouth coal,” or charcoal in the muffle door, which must, by means of a rake, be done quickly and completely; and the door of the muffle is fitted in its place. The whole of the openings in the furnace must be now closed, and the apparatus allowed to cool, during from one-half to three-quarters of an hour. At the expiration of this time the furnace is opened, and the assays taken out into a divided iron tray. If the buttons obtained appear rounded on the top, or have a slight depression in the centre, and can be readily removed from the cupels, it is an evidence of the operation having been properly conducted ; when, on the contrary, the buttons adhere firmly to the cupels, or throw out projections near the bottom, they are not fine; and if, in place of being convex and nearly spherical on ed upper surfaces, they exhibit a flattened appearance, it shows that the cupellation has been effected with the addition of an insufficient amount of lead. | It now only remains to clean and weigh the assays, and to compare them with a well-ascertained standard of comparison consisting of weighed quantities of silver, of which the degree of fineness has been previously determined, and which have been cupelled in the same furnace, and at the same time, as the unknown alloys. It will be found that, in all cases, a loss has been experienced, which is partly due to volatilisation of silver, and partially to absorption by the cupel. The amount of this loss will depend on the conditions under which the cupellations have been effected, and will be in a great degree influenced by the temperature which has been employed. The standards, or proofs, subjected to the same conditions as the assays themselves, will necessarily experience a corresponding loss, and afford data for correcting the results indicated by the balance. , In establishments where large numbers of assays of silver bullion are daily made, the process of Gay-Lussac for estimating silver by means of a standard solution of chloride of sodium is extensively LL2 516 SILVER. employed. As, however, this operation is rarely performed by the metallurgist, and comes rather within the province of the professional assayer, we refer for a description of it either to the work of the inventor of the process,* or to an article, chiefly translated therefrom, contained in Mitchell’s “ Manual of Practical Assaying.” * “Tnstruction sur Essai des Matiéres d’Argent par la Voie Humide,” par M. Gay-Lussac. Publiée par la Commission des Monnaies et Médailles. Paris. 1832, APPENDIX. A.— VOLATILITY OF GOLD AND SILVER. Ir has been long known to Metallurgists, that both gold and silver are, under certain circumstances, to some extent volatile; but Napier has shown that when an alloy of these metals is kept in a state of fusion at a high temperature, they are very distinctly so. By collecting the metallic vapours escaping from a crucible containing from twenty-five to thirty lbs. of melted. alloy (gold coin), the results obtained in two instances were respectively as follow :*— Vapour collected. Pure Gold in Vapour. grains. grains, 1 . —4 5 80 > . ° > . ° e . » 4 “50 a. —4 : 40 > e . . > ° ry ° > 41 0 Deposits obtained from top, middle, and bottom of a chimney thirty-five feet in height, attached to a small furnace used for fusing an alloy of silver and copper (silver coin), gave the following results :— Top. . Middle. Bottom, per cent. per cent. per cent, Metalic miver i: @ « S30 « UTS eg ye 20°95 Oxide of ,, eer aR roe i ee et OLE Deposits were also examined from the top, middle, and bottom of a chimney attached to a furnace in which an alloy of silver containing a con- siderable portion of gold was melted, with the following results :— | Top. Middle, Bottom, Metallic Silver . . . 29°380 . . . 389°160 . . . 48°750 Oxide of ,, Seat 2980 vee 4c ser SIO si (Tec 22 082 Goth net sae tt WII 2 ede Be WeGAOy eo. gS DEOF * Quarterly Journal of the Chemical Society, 1857, 518 APPENDIX. Makins has corroborated these results by experiments on deposits obtained from a flue attached to a muffle in which assays of an alloy of gold and silver had been made. 1,000 grains of this deposit gave— POLE ah Gs cat Sas Sey oe leew vy lee ales BL Ver eG kee Siete e beiad oe Sele Ge ee The lead carried off in the form of fume, during the metallurgical treat- ment of argentiferous galena, is invariably found to contain a certain pro- portion of silver, but the lead resulting from its re-treatment is always much less rich in silver than that obtained directly from the ores. The following results, obtained from samples of fume taken at different points along the course of a flue leading to the stack of a lead-smelting establishment, in which the work lead contained, on an average, twenty-six ounces of silver per ton, show the relative volatility of the two metals when subjected to the heat of a Castillian furnace.t From top of Flue. Lead. pier From bottom of Flue. Lead. ao Spee: a | Peso No cent 02, dwe. gr. || Xo po! oz. dwt, gr. 1 | Near Castillian Furnace .| 49 IN me. | 1 | Near Castillian Furnace .| 53 29 0 22 », Reverb. 4 4 20 3b 8 i 2 y, Reverb. = Pa a 29 6 8 | 100 ft. in advance of No.2} 70 | 8 5 8 | 3 | 100 ft. in advance of No.2} 638 3. 5-8 4 7 é te Mae we wo. ee ey - ; 3| 6L 4 3 98 5 5 ip 40 43 4 OW OG - 3 4} 49 | 217 0 6 z 5} 47 | 35 8 || 6 P: ‘ 5] 64 | «20g “4 3 3 Bh. 26 ft 8°68 ey * “A 6| 46 | 3 6 5 8 » ” 7| 40 2.-1.5 .|| 8 9s “3 74.088 112-5 9 - Mi Bf a8 B58 Aw “? i 8| 62-72 10 | Throat of Refinery. < «| 49 | 2237°8 | 10 Foot of Chimney .. .| 66 oe Ouro | B.—MINERAL STATISTICS OF VICTORIA FOR THE YEAR 1866.f Number of Quartz Miners employed in the different districts :— Dalian ee ge es a oe eee a eee a ee Beechworth aa 60 2S as GE Rae See DRE eg en co a) Ve get a Maryborough. 254 cx. is gas ee ee CSUIOMIAIMO ee a ae cask ee ee Oe AYAPRG OL TE a ee Se es 874 DOL a a eh A eee * Quarterly J eal 7 oe Chérical, ae 1860. + The lead obtained from re-smelting slags is also, unless it occurs in the form of lead matt, relatively much poorer in silver fad that obtained directly from the ores. ~ Mineral Statistics of Victoria for the year 1866: Melbourne. yy Oe een | ee ee cee ee ae APPENDIX. 519 Number of steam engines in operation during 1866 :— Alluvial mining engines, 480 ; aggregate horse-power, 9,981. Quartz mining engines, 510; aggregate horse-power, 9,231, Number of stamp heads, 5,437. Very full returns of the yield of gold from quartz veins have been obtained for the year 1866. It is not practicable to give an account of the yield from all the quartz put through the mills in the various districts, but accurate information has been received relative to 861,46813 tons, which gave 452,895 oz. 7 dwt ; or an average of 10 dwt. 16:2 gr. per ton :— Mining districts. Tons crushed. Total produce. Yield per ton. oz. dwt. dwt. gr. alee 2g, 8 eo, DUOe 1, og 9 GLO 4S) es. yA Bh Deseuworth . < 130,5192% ., 118,495 19 .-. 18 37 wanimurse. ©. 244.8076 ~~". 118743109... 9 16'8 Maryborough. 79,5528 . . 44,96714 . . ll 73 Castlemaine . . 124,3745 . . 85,662 8 .. 138 18° Mterat 2 a (S- 43,713 eR TS See. 1S ei kbs Ey Totals 861,4683% 459,895 7 WW 1672 The prices paid for treating quartz ranged from 4s. to 1/. 10s. per ton. Quantity of gold exported during the year 1866 as returned by the Customs Department, 1,479,194? ounces, * eturns show approximately the gold obtained from quartz veins and alluvial workings during the year 1866 to have been as follows :— Prom quiris Veils 9 oo tat +, « OAkOl7~ gunces ee alliaviak- Workings: coc. 2-4. 9681777” Total Gold exported . . 1,479°1947 ,, C.—ST, JOHN D’EL REY MINING COMPANY. The quantity of mineral raised from the mines, and the quantity of ore stamped during 1866, were as follow :— Tons. Miinswaleeised 2. < sah ed e ee BOT BST (frecptampeds, so v4 “6 + ee 4g , 607685 The quantity of killas and other inferior mineral rejected at Morro Velho during 1866 was 45,931 tons, or 43 per cent, of the quantity raised, The total produce of gold from the 23rd March, 1866, to the 23rd March, 1867, was 622,129 oitavas, The net profit on the working of the mines from 23rd March, 1866, to 23rd March, 1867, was 109,407/. 15s. 8d. The average yield of the ores at Morro Velho, for the year ending 31st December, 1866, was 9°780 oitavas per ton of ore stamped. By re- * In addition to the above, 407,394 ounces of New Zealand gold were shipped from this colony during the year, iy eee | APPENDIX. stamping with killas, and grinding (in arrastres), the refuse afforded in addition, 0:525, giving a total yield per:ton of ore a) during ses of 10 305 oitavas.. D.—DON PEDRO NORTH D’EL REY GOLD ae. COMPANY. “ ie Stone treated and Gold Patines Sor. sivdlue months siti Decomber 1866. MAQUINE. ‘ BAWDEN’S MINE. Piwere MINE. _ POTAL, : Eo ie eee Ce eee SE Oe ne Ores =~ aol, Ore. Gold. Ore... Gold: Ore. Gold. tons. oitavas. tons. oitavas. tons. oitavas. tons. ’ oitavas. 12,779 70,348 4,787 11,754 106 35 17,672 82,137 Tipe & eee Value of 82,137 oitavas of pt ey at Ss. 7d. es eh, Yt BORO Coabee 8 P's eee 4s 2 Profit. 3 4 4. eS ee The returns made and profits realised from these mines during the - four months of the year 1867, have been as follow :— Gold produced. Profit. : oitavas. £& Sead January. PG. oo sT, ORE ao eS ee eee Nebruary oe. ADSEIG os is eee Oe Mareh 9.0 3 83 ey © Q0j006... ns ee ae ee Aprils) A. 8 PDO) © pt OS ee eee Total . 63,564 £18,314 8 8 E.—RETURNS MADE FROM THE ANGLO-ITALIAN GOLD MINES SINCE 1863.* — The Val Toppa Gold Mining Company. Value. OZ, f 8. PSG 6S eos yea ov OD ad Os ke tan gia Sei eee 18 8 « F865. wires a OTE OID ~ on es oe ae ciel a ge Sa 1,400°925 © 2,0 gee? DAA OR 1 ae 4 Total since 1863 2,484°775 £8,789 8 10 Val Toppa has rane upon an average 1 oz. 5 dwt. of gold per ton of ore. The Vallanzasca Gold Mining Company. ee 2 ’ Value. é : Rete, en Dees So aes ROS ee toe SOL OOO: gird hate A a ee B8O5" PS iene TAO ATE Ro BBO a 1806 6 ow le “AV AOOD DS ene ee oe Oe ole Total yield of Gold since 1863 2,869°050 .. . . . . £8,864 5 10 ~ Vallanzasca has yielded upon an average 15 dwt. of gold per ton of ore, ’ * Furnished by Mr. J. C. Goodman. APPENDIX. 52t The Pestarena Gold Mining Company. Value. OZ. £& $0 Gs 1866 January, Gold received. 776°350 2,504 9 8 August a 815°375 2,688 0 8 October “5 556°650 1,806 9 8 December > 658°125 2,176 17 9 Total 2, 806500 £9,125 17 9 1867 January, Gold received . . 265°850 554°19 9 May .. . . 1,308°975 4,293 17 8 June ~f os «- 15154960 etc At ba Lo? Total 2,729°T75 £8,669 14 0 & Suede 1866 9,125 17 9 1867 8,669 14 0 Total eSrnige 1 9 The Pestarena ore has yielded 23 oz. of gold per ton. ¥.—-RETURNS OF GOLD AND SILVER BULLION ASSAYED IN THE UNITED STATES DURING THE YEAR 1866, ON WHICH THE GOVERNMENT DUTY OF ONE-HALF PER CENT. WAS PAID.* Bullion assayed. California . . $49,020, 256 Colorado 219, 860 Idaho . 535,105 Missouri 815 Nevada 15,272,546 New Jersey 13,688 New York 7,295, 803 Oregon 4,785,231 Pennsylvania 4,044,218 Rhode Island 2,211 Utah 60,278 Washington . 139,533 Total value EEE . $81,389,538 * The duty is only paid on bullion assayed for the first time. INDEX. A. ABERCROMBIE. « . Abrudbanya, Silver mines of . Addition of salt to Torta Africa, Gold districts of », _ Gold produced in Aguacatal gold mines Alabama, Gold i in Alexander Reef Allemont silver mine Allison Ranch vein . : ; Alotepec, Silver mining district of . Alps, Great Central Gold Mining Co. oT he aliver Wiines Of... -. « Alston and Weardale Workings : Altai Mountains, Silver mines of Amador County . fie », district, Silverin . », Quartz Mining Company », Silver mine . ee Amalgam, Native ot Sodium . ; Amalgamated copper plate, Use of . ‘ Plates > Amalgamation at Constante, Spain . - ,, Freiberg - Barrel process . Be Common pan . a Estufa : Be Hepburn and Peter- son’s pan ne of concentrated ores at Morro Velho zy of gold in pans ie 4 the battery . of roasted ore in pans aa Pan process . as separators ‘ F: Varney’s Pan . Wheeler’s . Amalgamator, Baux and Guiod’s. America, Central gold districts of Colonies, North Be | dis- Tiras Ol 2. « Gold fields of . 3 North, Silver mines of . . South, Gold districts of Analyses of auriferous pyrites . , native gold. Analysis of saltierra . Andreasberg, Silver mines neat 2? 29 PAGE Angel’s Camp : ees Anglo-Italian gold mines, Returns made since 1863 . . . Anglo-Mexican Silver Mining Co. Annaberg, Silver mines of. Antimonial silver Aorore, Gold fields of Ararat . , Argentiere silver mine . Ar gentifer ous and auriferous lead, Extraction of the precious metals from galena, Assay of . gossans of Cerro de Pasco... 3 lead, English system of tr eating Armens silver mine . Arquerite ‘ Arrastre, Descr iption of Se de marca . : rp Loss of mercury i ine. Asia, Central and Southern, Gold dis- tricts of... Pier ae », Gold pr oduced in . Assay of auriferous ores , », gold bullion : a Office, New York, gold coined ae pots at Pontgibaud : sx pailwer’ ore, Comstock vein . ry tSBIe % oes a Asuncion silver mine. , Atlantic or Appalachian g gold fields . Attwood’s system of ~ amalgama- tion Auckland . , Augustin’s process “for silver . Auriferous quartz veins, Age of . 24 sands, old and modern alluvial deposits . Austin silver mining district . Australia, Discovery of gold in + Gold fields of is »> produced in 4 5, Washing in “ mode of working gold . " power employed in work- ing gold. a scarcity of water for gold washing — . s * South, Gold districts of extracting 524 INDEX. PAGE Australia, System of Se crushing HT ary 0 MarR ea nT! bel Vein miningin. . > 166 Austrian Empire, Gold districts of . 24 x < >> produced in .., 127 », produce of gold . 26 Avonclift WG RIMS ca he Sa ee, B. PAmGuR Mine. be e eee OO Bahu vein . ise ee eet ee Ballarat gold Aalds 9 eo See Banat of Temeswar . ey a Renee » The silver mines of the . ay ae Bar diggings . Br ak 2) Barrel’ amalgamation, Nevada ~ a OSG »> ‘process of amalgamation a en Oe sa. UATE 0 Nea oe 93 Basalt-employed for mullers . . . 329 Batea, ° Description’ ) yee Ae Ae ee Baux and Guiod’s amalgamator Saab te Beach mining. . ay et ee Beechworth sold mines . a PGS Wad here! by Bella Raquel ‘Company yma? Ge 5 ree Bers tir > cn aes 3g eee - hee hench digoings =". ste be LD Bendigo gold Giatd * Spee ea 122,317 Beschertgliick silver mitie-.- .-, “5° “252 Big Oak F Te et A, a ck ae Biscaina silver-velm 7... 270; 279 Peerutarsiivercwc 2? 0 oy ue ee eee Blankets for washing A Aan meitiche e i A UR fed PERE hee en ge ee ae oe Bieck viltles” 20 echo... eee ED Blower, The Oe coo. ee ee Die heads; sah uo 2 oo ee phere Os Bodie aiattict ; os be Oe Bohemia,- Gold ie ite Ge et. ae “5 Silver niinesof°.s. G 208 Boitza silver vein . 258 Bolafios Silver Mining Company: “27, 277 Bolivia, Gold districts of . . 90 ts prodticed in.” Wye. play ae Silver gies Of 73" eros oe eee Borax‘Lake . 11 Bradford’s Separator, Description of 194 Brazil; Gold‘fields‘of* .° . 79 ge Cire MINI TN oe ete el i! yy proauccd i eee SP gs a PEOUDCLION Olgas 86 », results obtained from stamp: mo nills 65 213 British Columbia, Gold districts of. 98 ‘ », produced in. 197 a Gold Mining Company - : 117 ae Possessions, - Gold distr icts of 101 Bromide OD eilver. 7c. wer. Lene Bromyrite . . em rey pak? Buckingham Gold Company PE ep 8 Buller River . 125 Bullion cag ee in ‘United. States, LeCC SS 521 Bul Veins Se ys Ae Ts ge SE Buninyong Mining Company . Spiegen IK bg Buscones Bute County . Butschum silver vein C. JACHOEIRA Vein Calaveras County . Calcination of worked lead Calcining, Pontgibaud . California, Gold fields of . », produced in . ” 5, produce of 9 gg, WASHING 1 leit ” Quartz veins. se Richness of gold deposits i 0 APaleser the ‘oparalies of the principal quartz mills in 1861 ; ~ Vein mining in Canada, Gold districts of Canterbury, Province of Cape Claim ea! Capellina . . . » mine 56, 61 9 9 in Reese Europe, Gold produced i AD) -, Vice POE an Silver gines.of . a 6h Expenses at the Kongsberg mines . 255 Ne Real del Monte . . . 284 Extraction of gold from sulphides . 195 silver ores at Guanaxuato 330 ES precious metals from argentiferous and au- riferous lead . . . 448 A precious metals by bath of melted lead . . 427 99 79 F, PARLBANDS fit oe ce} pce eee oe Natzbay: silver Wein 6s). 6. & =o ADS Feistritz silversmine "541% 3." . “202 Filtration of mereury . . . . . 846 Fine grinding. . . 829 », stamping at Real del Monte . 361 Flat diggings . . - 129 Fluxes, Materials employed as, Wexico.,° 3 a Fis es Fondon . . Ot? oh ee ee France, Gold districts of . . he) oo. +)? DELWeD Ae Po a Oe Fraser river. £98 Freehold Gold Mining Company . . 33 Freiberg silver mines. - (QR9 », -Amalgamation at. .° 2°. S87 ye chlorination of ores . . . 865 ie composition ~ ,, , GS »» Distillation of amalgam at. 371 »» oss of mercury at’. <2 2 340 Refnmpat. . 2 G0 20 2 Be Freislebenite . ear 1250 French process of crystallisation . .. 459 Fresnillo silver ming= 7 44 © £255 8 furnace, Castillian . sieves 1 Bs = Description of . 442 = Clausthal % . 438 : Continental eeptag, Chargeor (5 Ae sa a0 35 URE ie) ee ee 3 DV UE Succ eae he it oe es Refining, Description of English . . Seer i! Roasting, Pontgibaud 5 eg Ricica of roasted ores in "Boxico . Uh OT Fiizes silver veins . ». 4 2 «» ‘ 88 G. Galeme. . - . §02 Galena, Argentiferous assay of 2. aod Galera... PS it tage Gard, Gold districts of ha? a. aii 19 Gardiner Gold Mining Company. . 33 Garnett and Mosely mines . . . 83 Gaudalcanal silver mine .. . . 262 Gem of the Sierras silver mine . . 309 River Mining Fegiow... | Fo Ge va Geology of Central America... 311 Georgia, Gold districts of . . . . 386 Germany ,, . 24 Goid, extraction of, from sulphides . 195 », Geological position of 4, 10, 30, 32, 40, 46, 57, Es 90, 104, 125 »» will nines. : 34 », in alluvial deposits cae 12 », large nuggets . er 28, 29 »» Mining; diagram of processes used in treating aes quartz . . » oe eee », Dative, Analyses sf Soph: 3 ee production of Africa . . . 127 Asi® : 5.0 5 oe Australias iat 0 Qe Austrian Empire26,127 99 99 99 99 99 29 & 3 Bolivia @ p22 ae i. Brazil. » 88, 127 a te BritishColumbia 127 - ae California . 66, 127 iG 37 Chili « PO, 127 = es Kast Indies. . 27 - % Europe. . 127 = 25 Merionethshir a 16 a Lg Mexico . 197 Morro Velho . 83 New Granada . 127 2 a NewSouthWales 120 New Zealand . 127 Noya Scotia. 96, 127 Peru ,. ¢is96eeeee os 3 Russia .. 24, 127 yo a United States 76, 127 ie ae Victoria. 2 wage es Wales: 6 a =e 5 refining . . 226 », regions of the Old World . Mee |) », .sources-of supply. 27) eee », veins, Formation of . 6, 12 ~ », not impoverished in depth 7,112 ,, volatility of . aya », washing, comparative costs of various methods . . > ee », Washing in California and Aus- tralia':as

» in arrastre a wt in Patio Sites » Silver 55 on working ores ‘in barrels, Nevada Carpe Glens Lunenberg . : Lyell River Lyon County . M. MACHINE employed for working tortas Machinery poate at Real del Monte it sad 341 283 528 Madagascar, Gold in. Magenta aqueduct : Magistral, Preparation of . Maine Boy’s tunnel . Malacates . Mammoth district ‘ Management of Tortas at “Zacatecas aiid Presai liane ped, 5: oad alae Manitowoc silver mine . Marienberg silver mines Mariposa County . 55 AOR EED: a sets he “5, 6, 47, 48 bi. Vel. Mariquita and New Granada Mining Company : Marlborough Marmato mines Marshall mine : Maryborough district Massachusetts Hill Massacre Bay. . Matakitaki diggings . Materials necessary for reducing silver ores by Patio process . McAlpine’s vein . . : McCulloch Gold Mining Company : Mellado silver mine . hep Melting and refining, Constante . »5° retorted gold Merced Mining Company : : Mercury, E mployment of, in Patio . = Loss of, in Patio process . Merionethshire, Gold i in Method of extracting silver ores of Comstock vein s, working Barrels, Constante ge Castillian furnace Mexican Silver- Mining rere : Mexico, Cupellation in. », Fusion of roasted ore in 5, MO Old MISTPICES Ole te 8 No si) 5 », Gold produced in . : », important silver mines of . »» Materials employed as fluxes are ome ae hs “ae », Roasting ores in », sale of silver ores in , », Silver-mines of a Bia in! Miar eyrite . Middle Hill silver veins » Yuba Canal esis Miners’ Inch : Mines, silver, of Alotepec ; Mining districts of Chili Moldawa silver mines Molino. . ‘Montana, Gold districts ene Ws silver mine Montezuma silver mine. ‘ Montgomeryshire, Silver ores of . Monthly amount of lead calcined, Pontgibaud. . poate Monton, Weight of . : Morro de Santa Anna Ghee ae “INDEX. PAGE : PAGE 98 | Morro Velho mine’ 2 —” Ge aeeenoee 153 », ~- Velho mine, Mode ofo occurrence 323 of: gold.at <3 eae 44 ‘ae Production of .gold at)... “242588 273 | Moulding amalgam, Mexico . . . 347 307 | ‘Mountain of. Alotepec .... . « . sll Mount Ophir vein. & =» 3) eee 339 | Murphy silver-vein . . oS. 309 260 48 N. 50 | INAGYAGITR .°. >.) 7S)iie0 ee 1 Nagyag silver vein . . ees 87 | Nagybanya, Silver mines of 5 4 nel ee 124 | National aqueduct . 9.4.) 3 Sis 87 | Native amaloam . . « 1: > 7: 33 >> + Silvera 2 2 2) Gr 113 | ‘Naumannite ~.«. .° 4° See 6) GW eNiélson ))! 2a iat P 124 124 | Neufang silver.mine -.. . ye 124 Neusohl, silver mines of . ¢s) esq. eee Nevada, "Barrel amalgamation in. . 386 323 ay County . . BO 51 tn EE discovery ‘of ‘silver i in. 296 24 »»- giant-silver vel <° ieee 274 ,, losson- working oresin Barrels 387 383 », Quartz Mining Company . 62 200 », Tesultsof Barrel amalgamation 385 50 >» settlers ss" ce.” 2 326 Stamping ores in=.—. 5G een 350 New Granada, Gold fields of . . . 87 15 Hh ee 5» produced in. .. 127 », Orleans mint . v4: 299 », South Wales, produce. of Gold 120 381 >, Wombat Hill '. . 2 see 444 », York assay office . . Barer | 271 ,, Zealand, geological remarks , ges | 500 m 3 Gold districts of: . .. 122 497 ie me » exported: . Gg sueerae ‘Mi 3 e » produced in 0am 127 ,, mode of working 125 267 Nicaragua, Gold in. 3... Nicolaiefsk silver mine, + = 7. eee 498 | Norambagua goldmine. . .. . 61 497 lode. . 166 275 North American colonies, “Gold dis- 266 a sid tricts of 2 oeeee 269 ie silver mines . . 266 250 - Carolina, Gold districts of. . 34 308 » River silvermine. . . 3804 152 »» Star Gold Mining Company a ee 152 sa) digs to SUL Ver IMINe sya. » 808 311 | Norway, Silver mines of . . 258 316 | Nouveau Monde Gold Mining Com- 258 pany . oie ae 329 | Nova Scotia, Gold districts of + er 67 3 »» -produced in «127 309 + Mining laws of . . 28 308 » produce of Bae a a ee 252 | Nufla furnace, The . . Sees Nuggets, Large . . 4, 29 484 | Number of Barrels employed, Con- 335 Stange ce pe ae oe ae 84(l, Nye County. (2258 22". ee es Se O. OBSERVATIONS on the crystallisation of lead by Mr. Hutchison . : Offenbanya silver vein , : Okanagan . Tia atd vem, Oneida gold mine Ser Ophir, Mount . »» Silver mine »» works, Cost of Barrel amalga- mation at, . Oravitza, Silver mines of . Oregon . LeCS cs) ( aa Ores from Comstock vein, ‘Composi- », of silver Otago ke Paciric Coast gold fields. Palladium gold é Pan . »» process, Cost of working 99 99 of amalgamation », Working in . Pans, Amalgamation of roasted ore in Partido system of silver mining . Pasilla . Patio », amalgamation, cost at Fresnillo », Guanaxuato 9? at Chemical reactions of 5, process for extracting silver Pattinson’s process : Pay dirt Perdida Peru, Gold fields ¢ of . 99 produced in . Philadelphia mint Philipofsk silver mine . . Pheenix Gold Mining Company Piedmont, Gold districts of Pine Tree mine ~. : Placer County », diggings . . poe ee Ace mnem s sah Pleiades, The, silver mine . Plumas County Polybasite .. Pontgibaud, Assay of pots at 99 Castillian furnace changes introduced since 1851. cost of crystallising ‘per * ton of market lead cost of improving lead >, Yoasting . a smelting . Crystallising at... Losses of lead and silver ae monthly amount of lead calcined . Reducing at . 122, INDEX. 529 PAGE PAGE Pontgibaud, rafinthg 488 pS re- -smelting slags 490 487 by roasting matt. 490 258 a slag waggons . 479 100 a Smelting at 477 115 = Summary of costs at 496. 56 Pr! treatment of calcined 50 dross 491 295 5, treatment of lead cinder 492 pe ‘5 fume . . 4992 Porkhura 258 389 Porpezite aad ea ‘| 258 Porpylite . . 289 303 | Port Phillip Gold Mining Company 114, 188 Portugal, Goldin. ar toe b, 388 Potosi, Silver mines of . 315 248 Poullaouen silver mine . 262 124 Precious metals, Extraction ‘of, by bath of Melted Lead. . . 427 Precipitation of silver 423 37 | Preparation of magistral - « 823 1 | Pride of the Mountain silver mine . 309 131 | Princeof Walesmine - . . ., , 16 405 fy ee ae ee ead th: 390 | Princeton vein : 49 401 | Processof extracting silve er , Augustin’s s 409 407 + 3° Von Patera’s 419 279 9 Ziervogel’s. 418 337 | Produce and profit of the Real del 334 Monte silver mines 286 357 | Production of silver mines of Cerro de 355 Pasco. 315 352 Chili. ...318 321 | Profit and produce of Real del Monte 455 silver mines . , 286 128 | Proustite 250 353 | Puddling box, Description of . 138 88 | Puy-de- Déme : ls 262 127 | Pyrargyrite 249 69 | Pyrites, auriferous + = 229 265 - », Analyses of e 198 35 20 Q. 48 BBN} Quartz Mix1s, Table of the principal, 40 : in California, in 1861 201 128 Bs mines. : 128 306°} Quebra Panella vein. . 82 65 | Queensland, Gold districts of. 121 250 486 R. 477 | Raspar , : 332 ? Ravenswood district . 305 480 | Rayas silver mine 273 Real del Monte, Cost of Barrel amal- 488 gamation . 385 485 “ fine stamping 351 476 i" machinery employed 283 479 <° results of Patio 486 amalgamation 357 . silver mines . .- 278 494 ee Silver Mining Com- pany 271 484 | Reducing, Pontgibaud . : 489 489 Reduction w orks, Arrangement of 406 MM 530. INDEX, PAGE PAGE Reduction works, Number of, Nevada 310 | San Domingo silver mine . 78 Reese River district . Bite 302 », Francisco mint . 70 mining region. 301 ,, Martin silver mines 276 Refining at Freiberg. Liga. is 372 », Nicolas s 276. "3 Pontgibaud . si 488 | Sandhurst district 113 _ 4, cost of in England 465 | Santa Ana silver mine . 319 », English process 461 5; Cecitha’ 24, 263 », furnace, English . 462 », Rosa ys 314 x) onweldas : 237 | Sarah Sands Piss 4 y . pil ver, Continental process 452 | Savage silver mine . 295, 304 Relampago silver mine . . . 263 | Savoy, Gold in ; . te Re-smelting slags, Pontgibaud 490 | Saxony, Silver mines of 258 Results of Patio amalgamation at Scarsdale workings . é 117 Real del Monte , 5. B57 | Scheidetrog. .* = ee 210 Retort . . 405 | Schemnitz silver mine’ ,: 2s 256 Retorting amaigam, Mexico 347 a Ores 0f * |) S20 renee 427 », description of process . 198 | Schladming silver mine 262 Re-treatment of tailings at Morro Schneeberg silver mines 260 Velho mines | RES 216 | Scorification 508 Revenue silver mine. ‘ 303 | Scotland, Gold in 17 Reverberatory furnace, Char ee for 437 | Segersfors silver mine 256 Description of 413 | Selbite . 250 Rhine, "Gold-heari ing sands of the 18 | Selenide of silver 249 Rhodium ro. Meee eee 1 | Semenofsk silver mines ; 265 River diggings 129 | Separation of gold and silver . 237 +) MMB «29 149 | Separators, amalgamation : 400 Roasted ores, sifting and er inding, Settlers, Nevada . 392 Constante : 378 | Settling pits . 183 Roasting, Avgustin’s " process 409 | Shaking tables, Description of 206 e furnace, ss cate De- Sheba silver mine : 309 scription of . 472 | Sierra Buttes Mining Company : 63 oS matt 490 »5 County 63 5 Pontgihaud : 472 | Sifting and grinding roasted or res, x silver ores, Mexico . 351 Constante Se Poe 378 we Von Patera’s process 419 | Silicate of silver . 250 a with salt ; 410 | Sil River, Gold- bearing sands of the. 20 Ziervogel’s process . 413 | Silver, Antimonial : 248 MUCKOr 2.755 8h Fy es te, 133 vo 2 ISIE 248 ,, Description of the . 191 5, bullion, Assay of 512 Rock sluices : 147 A Chloride of 249 Rohrerbiichel silver mine : 262 », combination of, with other Rohstein. 435 metals ‘ 249 Rossa Grande Gold Mining Company 85 ,, Commercial sources of. 250 Rough and Ready silver mine. 305 », concentration by erystallisa 9 . Stamping 2). > 328 tion . 455 Ruby silver . 249 y> fusion with roasted lead ores Russian Empire, Gold produced i in. 27 without metallic iron. 432 ,, possessions, Gold districts of 21 5, Geological position of 247, 251, 267 Russia, production of gold . . 24 re % in Nevada 288 Be 9 in Reese S. River mining region 301 SaLA SILVER MINES 4 256 i, Glance betas % 248 Sale of silver ores in Mexico. . 275 .,, Hill, Mines in - 308 Salor River, Gold-bearing sands of the 20 », mines of Central America. 311 Salt, Addition of, totorta, . « ; 336 - 55 316 ,, Roasting with . roeres - »» Norway 253 Saltierra . 325 of », the Old World 252 Salzburg, Gold district of . ; 25 & 55 oer 313 Samson silver mine. . 261 Be »» South America 313 San Antonio, District mines of 307 », mining districts of Kurope 251 ag bs ‘mine 5 78 » Native. ake 2 247 », Alvado silver vein . 276 55 ores 248 », Bernahé a ; 276 a ‘5 Assay of 504 ,, Carlos silver mine . 2638 =A ,, Composition of, Mexico 327 », Cleménte - ,, 276 3 », proper, Assay of . 505 Silver ores‘reduced by Real del Monte Company » 99 Smelting of auriferous » 99 Jreatment in Patio >> . realk district ; », Peculiarities of Great Com- stock vein . », Precipitation of . », produced by mines of Peru amd Bolivia oa: », produced in Mexico + Pe N orway, from ‘the Kongsberg mines. . », produced in United Kingdom », producing countries of the world, Yield of Be si 4 oduction of, in Hungary, Transylvania, and the Banat » Refining of, Continental Pie: CesS.. . » veins diminish in n richness i in depth, Mexico »» vein, Great Eastern », veins in Nye County Nevada Giant », of Alotepec a », Union district s ,WOlatility.of.... Slag waggons, Pontgibaud . Sleeping tables : : Sluice, Description of the . », ground , 3 ny OCk & or Baal As 7 Anne) ». : under-current. . Smelting at Pontgibaud See Saya ts Cae »» Mixture, Pontgibaud », Of auriferous silver ores », With lead ores, Bleiarbeit . Smoky Valley district Sneath, Clay, & Co.’s mill Sodium amalgam Soimanofsk mine . 99 29 Sombrerete, Furnace mixture em- ployed at : ‘ Silver mines near Sonneschmid . Soulsby’s vein. . Sources of supply of cold ee South America, Gold fields of ,, Australia, Gold districts of yy Carolina, Fe P Spain, Gold in : », Silver mines of . Spalling, Description of : Specific gravity of auriferous quartz Spitaler gangue , : Spring Hill mines St. John d’El Rey Mining Co. . 80, Stamping mills, Description of - in Australia . “I Brazil . is Hungary INDEX, PAGE 285 427 321 307 295 423 316 268 254 252 320 Stamping ores, Nevada. ey rough , Statistics, mineral, of Victori ia Stephanite . ; Sternbergite . . Strakes ae at Morro’ Velho mine . : Stromeyerite Suerte silver mine . : Sulphides, Extraction of gold from. os of silver . $5 Treatment of Summiar y of costs, Pontgibaud Summerhill het re ie ae Sutro’'Tunnel . Sweden, Silver mines sof : Switzerland, Gold districts of . Sylvanite es Szaszka silver mine . e PT: TABLE, Assay. . a for estimating the gold it in quar tz from its specific gravity », Mountain : », of yields of principal silver- pro: ducing countries . », showing amount of gold per ‘ton of ore corresponding with a given weight per 600 grains Tagus, Gold- bearing sands of the. Tahona . Tail sluice . : Tajos de Panuco silver vein Taking sample from torta . Tallulah silver mine. Tamworth . . Tasmania, Gold districts of Tcherepanofsk silver mine Tehuilotepec silver vein Telegraph mill Telluride of silver Tennessee, Gold in Tentadura . Teremakau. . Testing quartz for gold . Test, or cupel. . Thibet, Gold districts of Tina Cargadora ; : Tipoani washings. . Tlalpujahua Silver Mining Company Tom, Description of the . . Toplitza, Silver veins of Torta, Washing up >, Weight of Touchstone . Transylvania, Gold districts of Silver mines of Treading torta Treatment of amalgam, Constante 2 calcined dross, Pontgi- baud re lead cinder an », iume 532 Treatment of residues, Constante silver ores in Bolivia, previous to Spanish conquest : e sulphide of silver Trinidad mine Try-again Gold Mining Company Tub, Lixiviating . Tunnel sluice . Tuolumne County Turon: ~. Twin River “district, veins or”. Tyrol, Gold in Silver mines of the. 39 9? U. UNDER-CURRENT sluice Union district . United Extended Band of. Hope workings . i », Mexican Silver Mining Co. 99 e ,, . Hirst. gold comed in . 30 is ,, Gold coined at mints. 76 = ni » fields of the 29, 66 ma % », production of 76, 127 Utah, Gold in ee a eNOS, ¥. VALENCIANA silver mine : 271 Vallanzasca Gold Mining g Company 520 Val -Toppa ; 520 Vanderbilt silver vein 306 Vanderburg Mining Company 35 Varney’s pan, amalgamation . 395 Vascongada silver mine . 263 Vaso 500 Vein mining in Australia—California 165 os os Br erat A 203 Veneros . 90 Verdad de los Artistas silver mine 263 Veta de Colquirirca se 314 ms Pariarirca area 3" 5 », Grande silver vein 201, 2/0 ,, Madre : : - OOT tk Victoria, Act for management of gold : fields . 118 ;, Geological remarks on gold fields of .. " . 104 ,, Gold exported from . 1 - ,, fields of . 103 Vigra and Clogau 16 Villa Guttier silver mine 263 Virginia, Gold districts of . 32 Vitreous sulphide of silver . 248 Volatility of gold and silver HP he Voleano gold 1 mines . Benak Von Patera’s process 419 Vorédspatak, silver vein 258 Vulkoj , 258 INDEX. PAGE 383 W. WAIPORI mines Wakamarina . i 315 | Walchern silver mine 424 | Wales, Gold produced in 78 | Waller Gold Mining Company 118 | Wangapeka : 411 | Washing up torta, Guanaxuato . 149 . Zacatecas . 51 Fresnillo . 120 Washington district . 306° eS territory 25 | Washoe County . . 262 | Water, amount requir ed, cost of . »» Extraction of, from mines in Mexico. 5 146 eprom 7 thé Comatoek silver 305 vein, Analysis of, &e. > __ supply. 117 | Weighing . 971 Weight of a maoneen. torta. States, bullion assayed, in 1866 521 99 Welcome vein West’s furnace. Wet processes, Obtaining silver by . Wheeler’s pan, ere Whitehall mine Whitlatch Union silver mine . Whitman gold vein . Wicklow, Gold i Uh Wildberg, Cost of crystallisation at. 5 results obtained from Cas- tillian furnace. Wood consumed by the Virginia Mining Companies . Wood’s Point workings . Working in pans . : torta “hot” . 99 Work lead, Calcination of ' X. XANTHOCONE . Be YAURICOCHA . : Yield of the Potosi silees mines . 99 countries Yosemite silver mine Yuba County. . Yungas, Gold washings of. Li ' ZACATECAS, production of silver . Silver mines of Zalathna smelting works Ziervogel’s process Zigzag “riffles Zimapan silver mines Zméof silver mine R. CLAY, SON, AND TAYLOR, PRINTERS, LONDON. principal silver-producing 250 314 316 309 65 90 278 275 258 418 145 270 264 ESASESYSASYISVISV TSS ORES LESS % SIL. OOK SSW 5 NY DOs WANs iy YT Y fe a Yrgx l, . SV NINGNGNGS tas ESSA SESS Z ISU TISIINQY TGV KK KO ANY pat Bi GE, —] | Gi Ts ~ SLi y V4) \ f —nY 7 // i é ; x} Macy ! tf my foe S “s iv A | hat?’ SS 1/7 \ EB ‘Sk / i / 7 / , \ .\ Y, / \ if f \. ‘ Ne, y, Y Mi if is : fj a ff <> \ or 4 = SS = Seas Fe | ‘ SS 5S ee ee f — f = aH + > f \ cu / | / / $ eng; & ie * TANS VES TN i / * YY // SS | \ eS fi : ST, = / Ss fiers hy BROS, / J } . 5 he PLLA \/ / W/ 4 y I pages | > al ff —> ~~ \ ag ih aw / ) dry : = ~ 2 — zt = se | Sy SS a Z 1/7 SF ie [FF =P Saag — \. 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