I I.11~ A ea~~~~~ MANUAL OF INCLUDING OBSERVATIONS ON MINES, ROCKS, REDUCTION OF ORES, AND THE APPLICATIONS OF THE SCIENCE TO THE ARTS. WITH 260 ILLUSTRATIONS. DESIGNED FOR THE USE OF SCHOOLS AND COLLEGES. BY JAMES D. DANA, A. M., Member of the Soc. Caes. Nat. Cur. of Moscow, the Soc. Philomathique et Paris, the American Academy of Arts and Sciences at Boston, etc.; Author of a " System of Mineralogy." SEVENTH- EDITION. NEW HAVEN: PUBLISHED BY DUPrRIE & PECK. PHILADELPHIA: PECK & BLISS. Entered according to Act of Congress, in the year 1848, by DURRIE & PECK in the Clerk's Office of the District Court of Connecticut. PREFACE. IN the preparation of this Manual, the author has endeavored to meet a demand often urged, by making it, as far as possible, practical and American in character. Prominence has been given to the more common species, while others are but briefly noticed in a smaller type, or are mentioned only by name. The uses of minerals and their modes of application in the arts have been especially dwelt upon. The value of ores in mining, their modes of reduction, the yield of mines in different countries, and the various applications of the metals, have been described as minutely as was consistent with the extent of the work. The various rocks are in like manner included. At the same time, the subject has been presented with all the strictness of a scientific system. The classification adopted throws together ores of the same metals, and associates the earthy species as far as possible in natural groups. This order is preferred by very many teachers of the science, and has advantages which for many purposes counterbalance those of a more perfectly natural system. The account of the ores of each metal is preceded by a brief statement of their distinctive characters; and after the descriptions, there follow general remarks on mines, metallurgical processes, and other useful information. As the rarer mineral species are not altogether excluded, but are briefly mentioned each in its proper place in the system, the student, should he meet with them, will be guided by the Manual to some knowledge of their general characters, and aided in arranging them in his cabinet. [v PREFACE. The list of American localities appended to the work, the descriptions of mineralogical implements, and the notice of foreign weights, measures and coins, will be found convenient to the student. The author must refer to his larger work for more minute information 3n the localities of minerals and the associations of species-for full lists of synonyms-for tables for the determination of minerals-a more complete account of crystallography and its details-chemical formulas of species, and more numerous analyses, with their authorities —and a list of mineralogical works and journals. He has there expressed his indebtedness to the various Geological Reports of the different States, and also to the scientific journals of the country, for information on American minerals. In addition to these acknowledgments, he would mention his obligations to Prof. C. B. ADAMS, of Amherst, Mass., and Prof. M. TuoMEY, of Alabama, authors of Reports, the former on the Geology of Vermont, and the latter on that of South Carolina. Aid has been received in various ways from Prof. B. SILLIMAN, Jr., and much valuable information from Mr. A. A. HAYES of Lowel, Mass., H. KING of St. Louis, and S. S. HALDEMAN of Columbia, Pennsylvania. Ure's Dictionary of Arts, Manufactures, and Mines, has been a work of frequent reference, and the figures of a zinc furnace are from that volume. TABLE OF CONTENTS. CHAP I. —GENERAL CHARACTERISTICS OF MINERALS,. 13 CHAP. II.-CRYSTALLOGRAPHY: OR THE STRUCTURE OF MINERALS, 19 Fundamental forms of crystals,.... 23 Cleavage,...... 33 Secondary forms,...... 34 Compound crystals,.... 42 Dimorphism,.. * 44 Irregularities of crystals,..... 45 Measuring angles of crystals,.. 47 Massive minerals,..... 52 Columnar structure,... 52 Lamellar and granular structure,. o. 53 Pseudomorphous crystals..... 54 CHAP. III.-PHYSICAL PROPERTIES OF MINERALS. Luster,....... 55 Color,..... 56 Diaphaneity,-Refraction, and Polarization,.. 58 Phosphorescence,...... 61 Electricity and Magnetism,.... 62 Specific gravity,...... 63 Hardness,... 64 State of aggregation —Fracture,... 65 Taste-Odor..... 66 CHAP. IV.-CIHEMICAL PROPERTIES OF MINERALS,. 66 Action of acids,.... 66 Blowpipe,....... 67 CHAP. V. —CLASSIFICATION OF MINERALS, ~. 71 CHAP. VI.-DESCRIPTION OF MINERALS,... 76 1. Gases,..... 76 2. Water,...... 78 3. Carbon and compounds of carbon, o 80 4. Sulphur,..... 97 5. Haloid minerals,...,. 100 1. Ammonia,...... 100 2. Potassa,... 101 3. Soda,.. 102 4. Baryta,.... 108 5. Strontia,..,. 110 6. Lime,..... 11 7. Magnesia,.... 1 8. Alumina,. 1.27 Vi CONTiNTS. 6. Earthy- minerals, (silicates or aluminates,). 132 1. Silica,..,. 132 2. Lime,.... 141 3. Magnesia,... 143 1. Hydrous silicates,... 143 2. Anhydrous silicates,... 150.'4. Alumina,...... 158 1. Uncombined,.. 160 2. Combinqd, as aluminates,. 160 3. Hydrous combinations with silica,.. 161 4. Anhydrous combinations with silica,. 172 5. Combinations of a silicate and fluorid,.. 194 6. Combination of a silicate and sulphate,. 196 7. Silicate with a chlorid. 5. Glucina. 6. Zirconia. 7. Thoria. 7. Metallic ores. 1. Easily oxydizable metals,.. 202 1, 2. Cerium and Yttrium, 2.. 06 3. Uranium,... 209 4. Iron,... 211 5. Manganese,.. 233 6, 7. Chromium, Nickel,... 243 8. Cobalt,.... 247 9. Zinc,... 250 10, 11. Cadmium, Bismuth,.. 257 12. Lead,... 259 13. Mercury,... 270 14. Copper,.. 273 15. Titanium,... 290 16. Tin,..... 294 17. Molybdenum,.... 298 18. Tungsten,.... 299 19, 20. Vanadium, Tellurium,.. 300 21. Antimony,.. 301 22. Arsenic,..... 304 2. Noble Metals. 1. Platinum, Iridium, Palladium,.. 307 2. Gold,... 311 3. Silver,..... 319 8. Supplement to the description of minerals,. 329 CHAP. VII.-Rocas OR MINERAL AGGREGATES,... 335 CHAP. VIII. —CATALOGUE OF AMERICAN LOCALITIES OF MINERALS, 358 CHAP. IX.-BRIEF NOTICE OF FOREIGN MINING REGIONS,.. 377 CHAP. X.-MIYERALOGICAL IMPLEMENTS,... 382 CRAr. XI. -WEIGETS, MEASURES, AND COINS,. 384 TABLES FOR THE DETERMINATION OF MINERALS,... 388 r[fXEX,........415 GLOSSARY AND INDEX.OF TERMS.* ACIcmLAR, [Lat. acus, a needle,] 53. Assay. The material under chemAdamantine, 56. ical or blowpipe examination. Adit. [Lat. aditus, an entrance.] Astringent, 66. The horizontal entrance to a Asteriated. [Gr. aster, star.] Harmine. ing the appearance of a star Alkali. An oxyd having an acrid within. taste, and caustic; as potash, Augitic. Containing augite. soda., Auriferous. [Lat. -aurum, gold.) Alkaline. Like an alkali. Containing gold. Alliaceous, [Lat. allium, garlic,] 66. Axes, 24; of double refraction, 59. Alloy. A mixture ofdifferent metals (excluding mercury) by fusion Basaltic, 339. together. Also, the metal used Bath stone. A species of limestone; to deteriorate another metal by called also Bath oolite; named mixture with it. from the locality, in England. Alluvial. [Lat. alluo, to wash over.] Bevelment, beveled, 35. Of river or fresh-water origin. Bitter, 66. Amalgam. rGr. malagmna, a sof- Bittern, 106. tened substance.] A compound Bituminous. Containingbitumen; of mercury and another metal. like bitumen. Amalgamation, 326. Bladed. Thin blade-like. Amorphous, [Gr. a,not, and morphe, Blast furnace, 233. shape,] 54. Blowpipe, 67; tests, 69, 70: impleAmygdaloidal, 339. ments, 68, 69. Anhydrous. [Lat. a, not, and Blue-john. Name for fluor spar, hudor, water.] Containing no used in Derbyshire, where it often water. has a bluish-purple color. Arborescent. [Lat. arbor, tree.] Botryoidal, [Gr. botrus, abunch of Branching like a tree. grapes,] 53. Arenaceons. [Lat. arena, sand.] Boulder, bowlder. Loose rounded Consisting of, or having the gritty mass of stone. nature of, sand. Breccia. Argentiferous. [Lat. argentum, Brittle, 53, 65. silver.] Containing silver. Argillaceous. [Lat. argilla, clay.] Calcine. [Lat. caIx, burnt limeLike clay; containing clay. stone.] To heat, in order to drive Arsenical odor, 66. off volatile ingredients, and make Asparagus green. Pale green, with easy to be broken or pounded. much yellow. Calcination. The process of calAssay. [Same etymology as essay.] cining. To test ores by chemical or blow- Carat, 82. pipe examination; said to be in Carbon. Pure charcoal. the dry way, when done by means Carbonate. A salt containing carof heat, (as in a crucible,) and in bonic acid. Carbonated; conthe wet way, when by means of taining carbonic acid, as carboacids and liquid tests. nated springs. * The number after a word signifies the page where it is explained. The etymology is given in brackets, wherever it was deemed important. Viii GLOSSARY AND NEEJ X OF TERMS. Carbonize. To convert into char- Delicate delineations branching coal. like a tree; due to infiltration of Carburet. A compound of an ele- oxyd of iron or manganese. ment with carbon, not acid. Density. Specific gravity. Catalan forge, 237. Desiccate. To dry, to exhaust of Celandine green. Green with blue moisture. and gray; from the plant called Diaphaneity, 58. celandine. Dichroism, 57. Cementation, 238. Dimetric system, 32. Chalybeate. Impregnated with Dimorphism, 44. iron, 80. Divergent, 53. Chert. A siliceous stone containing Disintegrate. To fall to pieces; a some lime; also, hornstone. result of exposure and partial deChlorid. Combination of an ele- composition. ment with chlorine. Disseminated. Scattered through Chloritic. Containing chlorite. a rock or gangue. Chromate. A salt containing chro- Dodecahedron, rhombic, 25; isosmic acid. celes, 39, fig. 65; pentagonal 3 7; Cinereous. [Lat. cinis, ashes.] scalene, 40. Resembling ashes. Dolomitic. Pertaining to dolomite. Cleavage 33. Dressing of ores. The picking and Coke, 90. sorting of ores, and washing preColumnar, 52. paratory to reduction. Compound crystals, 42. Drusy, 54. Conchoidal, 65. Dull, 56. Coralloidal. Having a resemblance to coral. Earthy. Soft like earth, and withCretaceous. [Lat. creta, chalk.] out luster. Pertaining to chalk. Ebullition. The state of boiling. Cropping out. The rising of layers Effervescence, 67. of rock to the surface. Effloresce. To change to a state Crucible. [Lat. crux, a cross.] A of powder, by exposure; arises pot made of earth or clay for from the escape of water. melting, or reduction. Elastic, 53, 65. Electricity ofminCruciform, [Lat. crux, a cross,] erals, etc., 62. 43. Elements, 72. Crystal, [Greek krustallos, ice,] 19; Ellipsoid, 42. systems of crystallization, 24, Elutriation. [Lat. elutrio,to pour 32. from one vessel to another.] Cube, 25. Mixing a powdered substance Cupel, cupellation, 317, 328. (as powdered flint) with water, Cupreous. [Lat. cuprum, copper.] and then after the coarser partiContaining copper. cles have subsided, carefully deCurved crystals, 42. canting the liquid and putting it Decrepitate. To crackle and fly away to settle, in order to obtain apart when heated. the impalpable powder which is Deflagrate. To burn with vivid finally deposited. combustion. Elvan. In Cornwall, the granite Deliquesce. To change to a liquid, masses forming broad veins in on exposure; arising from the the killas, and containing the attraction of moisture. stockwerks. Dendritep. [Gr. dendron, tree.] Enamel. A glass having an ap GLOSSARY AND INDEX OF TERMS. iX. pearance like porcelain, or like Granular. Consisting of grains. the surface of a tooth. Granulate; to reduce to grains. Evaporate. To become a vapor; to cause to become a vapor. Hackly, 65. Even fracture, 65. Hardness, scale of, 64. Exfoliate. To separate illto thin Hemihedral forms, 37. leaves, or to scale off. Hepatic. [Gr. hepar, liver.] Hav. ing an external resemblance to Fault. Dislocation along a fissure, liver. as often in coal beds, 87. Hexagonal prism, 27. Feldspathic. Containing feldspar Hexagonal system, 33. as a principal ingredient; con- Homogeneous. Of the same texsisting of feldspar. ture and nature throughout. Ferruginous. [Lat. feblrum, iron.] Hyacinth red. Red with yellow Containing iron. and some brown. Fetid, 66. Hyaline. [Gr. hualos, glass.] ReFibrous, 52. sembling glass in transparency Filament. A thread-like fiber. and luster. Finery furnace. A furnace used Hydrated. [Gr. hudor, water.] in the conversion of cast iron into Containing water. bar iron. Filiform, [Lat. Jilum, a thread,] 53. Ignition. [Lat. ignis, fire.] The Flexible, 53, 65. state of being so heated as to give Fluate. Containing fluoric acid. out light; at a red or white heat. Flux, [Lat. fluo, to flow,] 69. Impalpable, 53. Foliaceous, 53. Implanted crystals. Attached by Forceps, Platinum, 69. one extremity. Fracture of minerals, 65. Incandescence. White heat. Friable. Easily crumbling in the Incrustation. A coating of mineral fingers. matter. Fundamental forms, 23. Indurated. Hardened or solidified. Furnace, blast, 233; reverberatory, Infiltrate. To enter gradually, as 327; Catalan, 237. water, through pores. Infusible. In mineralogy, not fusiGallery. A horizontal passage in ble by means of the simple blowmining. pipe. Gangue, 204. Inspissate. To thicken. Gelatinize, 67. Intumesce. To froth. Geniculate. [Lat. genu, knee.] Investing. Coating or covering, as Bent at an angle, 43. when one mineral forms a coatGeode. [Gr. gaeodes, earth-like.] ing on another. A cavitv studded around with Irised. [Lat. iris, rainbow.] Havcrystals or mineral matter, or a ing the colors of the spectrum. rounded stone containing such a Iridescence, 57. cavity. Isomorphism, isomorphous, 74. Glance. [Germ. glanz, luster.] Certain lustrous metallic sulphu- Juxtapose. To place contiguous. rets of dark shades of color. Glimmering. Glistening, 56. Killas. In Cornwall, the schistose Globular, 53. rock in which the lodes occur. toniometer, common, 47S; reflecting, 50. Lamellar, 53. X GLOSSARY AND INDEX OF TERMS. Lapidification. [Lat.lapis, astone.] Massive. Compact, and having no The process of changing to stone. regular form. Lapilla. Small volcanic cinders. Matrix. [Lat. matrix, from mater, Lavender-blue. Blue with some mother.] The rock or earthy red and much gray. material, containing a mineral or Leek-green. The color of the metallic ore. leaves of garlic. Metallic, 55, 56. Metallic-pearly, Lenticular. Thin, with acute edges 55. Metallic-adamanltine, 56. something like a lens, except that Metalliferous. Yielding metal. the surface is not curved. Metallurgy. [Gr. metallon, and Leucitic. Containing leucite. ergon, work.] The science of Levigation. [Lat. levis,light.] The the reduction of ores. process of reducing to a fine Micaceous, 53. powder. Mineralized. Changed to mineral Liquation. [Lat. liquo, to melt.) by impregnation with mineral The slow fusion of an alloy, by matter. Also being disguised in which the more fusible flows out character by combination with and leaves the rest behind, 328. other substances; thus used with Lithographic stone. A compact regard to metals when in combigrayish or yellowisgraray lime- nation with sulphur, arsenic, carstone of very even texture and bonic acid, or anything that affects conchoidal fracture; used in lith- their malleability and other qualography. That of Solenhofen, ities. near Munich, is moQst noted. Molecules, 42. Lithology. [Gr. lithos, stone, and Molybdate. A salt containing logos, a discourse.] Mineralogy. molybdic acid. Lixiviate. [Lat. lixiviumr, lye.) Monoclinate, 33. To form a lye, by allowing water Monometric, 32. to stand upon earthy or alkaline Mountain limestone. A limestone material, and draining it off be- of the lower part of the coal selow, after it has dissolved the sol- ries; called also carboniferous uble ingredients present. limestone. Lode. [Sax. Iosdan, to lead.] In Muffle, 317. mining, a vein of mineral substance; usually a vein of metallic Nacreous. Like pearl. ore. The lode is said to be dead Native metal, 202. when the material affords no Nitrate. A salt containing nitric metal. acid. Lodestone, 217. Nitriary, 102. Nucleus. The center particle or Macle. A compound crystal, or one mass around which matter is ag, having a tesselated structure. gregated. Magnesian. Containing magnesia. Magnetism of minerals, 63. Ochreous. Like ocher. Malleable, [Lat. malleus, a ham- Octahedron, pp. 23, 25, 26. mer,] 65. Octahedral. Having the form of an Mammillary, [Lat. mammilla, a octahedron. little teat,] 53. Odor of minerals, p. 66. Manganesian. Containing man- Oolite. [Gr. oon, egg,] p. 349. ganese. Opalescence, p. 57. Marly. -Having the nature of marl; Opaline. Like opal. containing marl. Opa!ized. Changed to opal. GLOSSARY AND INDEX OF TERMS. Xi Opaque, p. 58. Quartzose. Containing quartz as Ore, 202. Also, by miners, a dis- a principal ingredient. seminated ore and the including stone together; the term?net- Radiated, 53. al is often used for the pure ore. Rake-vein. A perpendicular minOxyd, 73. eral fissure. Oxydizable,. Capable of combining Rectangle, 24. with oxygen, Reduction of ores, 204. Oxydating flame, 68. Reduction flame, 68. Refraction, 58. Pearly 55. Refractory. Resisting the action Percolate. To pass gradually of heat; infusible. through pores, Refrigerate. To cool. Phosphorescence, 61. Regulus. The pure state of a Pisolitic, [Lat. pisum, a pea,] com- metal, as regulus of antimony. posed of' large round grains or Reniform. [Lat. ren, kidney,] 53. kernels, of the size of peas. Replacement, 35. Resinous, 55. Pistachio-green. Green with yel- Resplendent. Having a brilliant low, and some brown. luster. Plastic. Adhesive, and capable of Reticulated. [Lat. rete, a net,] being: moulded in the hands. 52, 54. Plumose. Having the shape of a Reverberatory furnace, 327. plume, or feather. Rhombohedron, 27. Polarisation, 60. Riddling or sifting of ores. PutPolarity, 62. ting the broken or pulverized ore Polychroism, 57., in a seive, and plunging the seive Play of colors, 57. into water, by which, the whole Plutonic rocks. Granite and allied powdered material is raised by crystalline rocks. the water and the metallic part Polyhedral. [Gr. polus, many, and sinking first, may be separated hedra face.) Havingmany sides. to a great extent from the rest. Polymorphism, 44. Roasting. Exposing to heat in Porous. Having minute vacuities, piles, or in a furnace, and thus visible or invisible to the naked driving off any volatile ingredient.. eye; a loose texture, allowing water to filtrate through. Saccharoid. [Gr. sakchar, sugar.] Porphyritic. Like porphyry, 340. Having a texture like loaf sugar. Prisms, 23. Saline, (Lat. sal, salt.) Salt like; Pseudomorphous, 54. containing common salt. Puddling Furnace. A reverbera- Salt. In chemistry, any combinatory furnace, used in converting tion of an acid with a base, 74. cast into bar iron, after the finery Scale of hardness, 64. furnace. Schlich. The finely pulverized ore Pulverize. [Lat. pulvis, dust,] to and gangue. reduce to powder. Schistose. Havinga slatystructure. Pulverulent. Like a fine powder Scopiform, (Lat. scopa, a broom.) slightly compacted. Like a broom in form. Pyritous. Having the nature of Scoria, (L. scoria, dross,) 205, 341. pyrites, 212. Secondary forms, 34. Sectile, 65. Pyro-electric, 62. Semitransparent, 58. Shaft. A vertical or- much inQuartation, 318. clined pit, cylindrical in form. Xil, GLOSSARY AND INDEX OF TERMIS. Shale, 341. Shining, 56. Tertiary strata. Strata more reSilicate, 74. cent in age than the chalk, and Siliceous. Consisting of, or con- antecedent to the recent epoch. taining silex, or quartz. Tesselated, (Lat. tesselatus, cheSilky, 56. quered.) Chequered. Silurian. A term applied to the Tesseral system, (Lat. tessera, a fossiliferous rocks, older than four square tile, or dice,) 32. the coal series. - Tetrahedron, (Gr. tetra, four, heSlag, 205. dra, face,) 37. Smelting of iron ores, 233. Titaniferous. Containing titanium. Spathic, (Germ. spath.) Like spar. Transition rocks. The older siluSpar. Any earthy mineral having rian, which were formerly supa distinct cleavable structure and posed to contain no trace of fossome luster, as calcareous spar. sils. Stalactitic, (Gr. stalazo, to drop or Translucent, 58. distil,) 54, 116. Transparent, 58. Stalagmite, 116. Triclinate, 33. Specific gravity, 63. Trimetric, 33. Splendelt, 56. Trimorphism, 44. Splintery. Having splinters on a Truncation, truncated, 35. surface of fracture. Tufaceous. Like tufa, 347. Stamping. Reducing to coarse Tuyeres, or twiers, 234. fragments inll a stamping mill. Twin crystals, 42. Stellated, (Lat. stella, star,' 52. Strata. A series of beds of rock. Unctuous. Adhesive, like grease. Streak, streak-powder, 56. Ustulation. [L. ustulatus, scorchStriated. Lined or marked with ed, or partly burnt.] Roasting parallel grooves, more or lees of ores. regular. Stockwerks. In Cornwall, works Veins. In miner's use, small lodes. in beds and veins of ore. The In geology, any seams of rock works in alluvial deposits are dis- material, intersecting strata crosstinguished as stream-works. wise. Sub. In composition, signifies be- Vein-stone. The gangue of a metneath; also,.somewhat, or imper- al or mineral. fectly, as submetallic, means im- Verdigris-green. Green inclining perfectly metallic. to blue; the, color of verdigris. Sublimation, (Lat. sublimis, high.) Vesicular. Containing small vaRising in vapor, by heat, to be cuities. again condensed. Viscous, 65. Submetallic, 55. Vitreous, (Lat. vitrum, glass,) 55. Subtranslucent, 58. Vitrification. Conversion to glass. Subtransparent, 58. Volatile. Capable of passing easiSubteirrand. A name given to ly to a state of vapor. Bovey coal, or brown coal. Washing of ores. Exposing theL. Subvitreous, 55. after stamping, (or before if in Sulphate. A salt containing sul- fragments,) to running water, phuric acid. which carries off the earthy maSulphureous, 66. terial, it being lighter than the Sulphuret. Combination of a met- ore. al with sulphur. Zeolitic. Having the nature of a Tarnish, 57. zeolite, 163. MINERALOGY. CHAPTER I. GENERAL CHARACTERISTICS OF MINERALS. Relations of the threcDepar'men'sof Nature. Viewing the world around us, we observe that it consists of rocks, earth or soil, and water; that it is covered with a large variety of plants, and tenanted by myriads of animals. These three familiar facts lie at the basis of three primary branches of knowledge. The animals, of whatever kind, from the animalcule to man, give origin to that. branch of science which is called Zoology; the various plants, to the sci. ence of Botany; and the rocks or minerals, to Mineralogy. The first two of these departments embrace all natural objects that have life, and treat of their kinds, their vari. ties of structure, their habits, and relations. The third branch of knowledge, Mineralogy, relates to inanimate nature. It describes the kinds of mineral material forming the surface of our planet, points out the various methods of distinguishing minerals, makes known their uses, and explains their modes of occurrence in the earth. Importance of the Science of Mineralogy. To the un. practiced eye, the costly gem, as it is found in the rocks, often seems but a rude bit of stone; and the most valuable ores may appear worthless, for the metals are generally so disguised that nothing of their real nature is seen. There is an ore of lead which has nearly the color and luster of Glau. ber salt; an ore of iron that looks like sparry limestone; an ore of silver that might be taken for lead ore, and another that resembles wax. These are common cases, and What classes of natural objects exist? Of what does Zoology treat? What Botany? Of what does, Mineralogy treat? What advantages result from the study of minerals? 2 14 GENERAL CHARACTERISTICS OF MINERALS. consequently much careful attention is required of the student to make progress in the science. Moreover, a great proportion of the mineral species are of no special value, and they occur under so many forms and colors that close study is absolutely necessary in order to be able to distinguish the useless, and avoid being deceived by them; for such deceptions are common and often lead to disastrous consequen. ces in mining. The science of Mineralogy is, therefore, eminently practical. Moreover, the very existence of many of the arts of civilized life, depends upon the materials which the rocks afford. Besides the metals and metallic ores, we here find the ingredients for many common pigments, and for various preparations used in medicine; also the enduring material so valuable for buildings and numberless other purposes: more. over, from the rocks comes the soil upon which we are dependent for food. At the same time, the student of Miner. alogy who is interested in observing the impress of Infinite wisdom in nature around him, finds abundant pleasure in examining the forms and varieties of structure which miner. als assume, and in tracing out the principles or laws which Creative power has established even throughout lifeless mat. ter, giving it an organization, though, simple, no less perfect than that characterizing animate beings. What is a Mineral? It has been remarked that Mineralogy, the third branch of Natural History, embraces every thing in nature that has not life. Is, then, every different thing not resulting from life, a mineral? Are earth, clay, and all stones, minerals? Is water a mineral? All the materials here alluded to properly belong to the mineral series. The minute grains which make up a bank of clay or earth, are all minerals, and if their characters could be accurately ascertained, each might be referred to some mineral species. It is evident, however, that the clay itself, unless the grains are all of one kind, is not a distinct species, though mineral in composition: It is a comrn. pound mass or an aggiegate of different mineral grains; and this is true of all ordinary soil and earth. In the same manner very many rocks are aggregates of two or more minerals in intimate union. Mineralogy distinguishes the species, and enables us to point out the ingredients which are mixed in the constitution of such rocks. It searches for specimens that Is clay a mineral? What is the nature of many rocks? GENERAL CHARACTERISTICS OF MINERALS. 15 are pure, and undisguised, ascertains their qualities and their varieties, and thus prepares the mind to' recognize them under whatever circumstances they may occur. Water has no qualities which should separate it from the mineral kingdom. All bodies have their temperature of fusion; lead melts at 612~ F.; sulphur at 226~ F.; water at 32~; mercury at — 39~. No difference therefore of this kind can limit the mineral departments. Ice. is as properly a rock as limestone; and re the temperature of our globe but a little lower than it is, we should rarely see water except in solid crystal-like masses or layers. Our atmos. phere, and all gases occurring in nature, belong for the same reason to the mineral kingdom. Several of the gases have been solidified, and we can not doubt that at some specific temperature each might be made solid. We can not, therefore, exclude any substance from the class of minerals because at the ordinary temperature it is a gas or liquid. Quicksilver with such a rule would be excluded as well as water. A mineral, then, is any substance in nature not organized by vitality, and having a homogeneous structure. The first limitation here -stated-not organized by vitality-excludes all living structures, or such as have resulted from vital powers; and the second-a homogeneous structure-excludes all mixtures or aggregates. The different spars, gems, and ores are minerals, while granite rock, slate, clay and the like, are mineral aggregates. This compound character is apparent to the eye in granite, for there is no difficulty in picking out from the mass a shining scaly mineral, (imica,) and with more attention, semi-opaque whitish or reddish particles (feldspar) will be easily distinguished from others (quartz) that have a glassy appearance. It is a popular belief, that stones grow. Yet the absence of any proper growth is the main pboint distinguishing min. erals from objects that have life. Plants and animals are nourished by the circulation of a fluid through their interior; in plants, we call the fluid sap; in animals, blood; and in. crease or growth takes place by means of material secreted firom this circulating fluid. The living being commences with the mere germ, and grows through youth to nmaturity; Why should water and gases rank with minerals. What is a mineral? What limitations are here implied? What is the nature of granite? 16 GENERAL CHARACTERISTICS OF MINERALS. and when this fluid finally ceases to circulate, it dies and soon decays. Minerals, on the contrary, have no such nourishing fluid. The smallest particle is as perfect as the mountain mass. They increase in size only by additions to the surface from somne external source. The deposit of salt forming in an evaporating brine, has layer after layer of particles added to it, and by this mode of accumulation, its thickness is attained. Beds of an ore of iron, called bog iron-ore, are sometimes said to grow. They do in fact increase in extent. Rills of water running from the hills wash out the iron in the rocks they pass over, decomposing and altering the condi. tion of the ore, and carry it to low marshy grounds. Here the water becomes stagnant, and gradually the iron is deposited. This bog ore, as the name implies, is found mostly in low marshy places, and often contains nuts, leaves, and sticks, changed to iron ore. The increase here is obviously by ex. ternal additions. In limestone caverns, and about certain lakes and streams, the water contains much carbonate of lime. As it evapo. rates, layer after layer of the lime is deposited, till thicli beds are sometimes formed. In caverns, the water comes dripping \through the roof, drop by drop, and each drop as it dries, deposits a little carbonate of lime. At first it forms but a mere wart on the surface; but it gradually lengthens, till it becomes a long tapering cylinder, and sometimes the pendant cylinder, or stalactite, as it is called, reaches the floor of the cave, and forms a column several feet in diameter. It thus appears that minerals increase, or enlarge, by accretion, or additions to the surface only. They decrease, or the surface is worn away, by the action of running water and other agents. When they decay, as sometimes happens fiom contact with air and moisture, or some other cause, the change begins with the surface, and results in producing one or more different minerals. The line of demarkation, therefore, between living beings, and minerals or inorganic matter, is strongly drawn. Characters of fiZinerals. In pursuing the subject of minWhat are the different modes of increase in the animate and mineral kingdoms? Mention examples of increase in mineral substances, and explain the mode. GENERAL CHARACTERISTICS OF MINERALS. 17 erals, there are various qualities presented for our study. We observe that stones or minerals have color; they have hardness in different degrees, from being soft and ilnpressible by the nail, to the extreme hardness of the diamond; they have weight; they have luster, from almost a total absence of the power of reflecting light to the brilliancy of a mirror. Some are as transparent as glass and others are opaque. A few have taste. These are the most obvious characters, and characters to which the mind would at once appeal in distinguishing species. Other characters of equal importance are found in the internal and external structure of minerals. On examining a piece of coarse granite, we find that each scale of mica may be split by the point of a knife into thinner leaves. Here is evidence of a peculiar structure, called cleavage; and wherever mica is found, this peculiarity is constant. The feldspar in the same rock, if examined with care, will be found to break in certain directions with a smooth, or nearly smooth plain, surface, showing a luster approaching that of glass, though somewhat pearly. It is true of feldspar also, that this cleavage is a constant character for the species, as regards direction and facility. In nearly all minerals, this kind of structure, more or less perfect in quality, may be distinguished. In a broken bar of iron the irregularity of the grains proceeds from this cause. In granular marble, although the mass as a whole has no such structure, the several grains if attentively examined will be seen to present a distinct cleavage structure and consequent angu. lar forms. In finer varieties, the grains may be so small that the characters cannot be observed; or again the texture of the mass may be so compact that not even grains can be distinguished. This cleavage, then, is a peculiarity of internal structure. It is intimately connected with another fact,-that these same minerals often occur under the form of some regular solid with neat plane surfaces; and are finished with a symmetry and perfection which art would fail to imitate. These forms are their natural forms, and every mineral has its own dis. tinct system of forms. The beauty of a cabinet of minerals arises to a great extent from the variety of forms and What physical characters are to be observed in the study of minerals? What character depends on internal structure? Mention exainples and explain. What other character depends on structure? 2* 18 GENERAL CHARACTERISTICS OF MVINERALS. high finish of these gems of nature's workmanship. The mineral quartz sometimes occurs in crystals consisting of two pyramids united by a short six-sided prism, and they have generally the transparency and almost the brilliancy of the diamond, whose name they bear in common language. The "diamonds" of central New York, and many other localities, are of this kind. In other cases a large surface of rock sparkles with a splendid grouping of the pyramidal glassy crystals. We might draw other illustrations fiom almost all the mineral species. But this will suffice to show that in ad. dition to the physical characters above mentioned, there are others dependent on structure, which afford distinctions o) species, apparent both in external form and internal clea vage. Still other characters are derived from subjecting species to the action of heat, and to acids or other re-agents. One mineral, when heated, melts; another is infusible, or fuses only on the edges; another evaporates. By such trials, and others hereafter to be described, we study minerals in a different way, and ascertain their chemical characters. This mode of investigation more minutely pursued, leads to a knowledge of the constitution of minerals, a branch of study which belongs properly to Analytical Chemistry: the results are of the highest importance to the mineralogist. It is perceived, therefore, that the learner may (1) exam. ine into the peculiarities of structure among minerals; (2) he may attend to the physical characters depending on light, hardness, and gravity; (3) he may acquaint himself with the e/fects of heat and chemical re.agents-the chemical char. acters. These are three sources of distinctions giving mutual aid, and a knowledge of all is necessary to the miner. alogist. To learn to distinguish minerals by their color, weight, and luster, is so far very well; but the accomplishment is of a low degree of merit, and when most perfect, makes but a poor mineralogist. But when the science is viewed in the light of Chemistry and Crystallography, it becomes a branch of knowledge, perfect in itself, and surprisingly beautiful in its exhibitions of truth. We are no longer dealing with pebbles of pretty shapes and tints, but with objects modeled by a Divine hand; and every additional fact becomes to the mind a new revelation of His wisdom. Mention examples. What other characters are there? Enumerate the kinds of characters presented by minerals. CRYSTALLOGRAPHY. 19 In the study of this science, the learner will be introduced first to the structure of minerals. The subject is treated of under its usual name, crystallography. CHAPTER II, CRYSTALLOGRAPHY: OR THE STRUCTURE OF MINERALS. Crystals: Crystallization. The regular forms which minerals assume are called crystals, and the process by which their formation takes place, is termed crystallization. Crystallization is the same as solidification. Whenever a liquid becomes solid there is actual crystallization. Under favorable circumstances regular crystals may form; but very commonly the solid is a mass of crystalline grains, as is the case in statuary marble, or a loaf of white sugar. In the case of the marble, crystallization commenced at myriads of points at the same instant, and there was no room for any to expand to a large size and regular outline. When on the contrary, the process is slow, simple crystals often increase to a large size. We may understand this subject of crystallization by watching a solution of salt, as it evaporates over a fire. After a while, if the process is not too rapid, minute points of salt appear at the surface, and these continue enlarging. They are minute cubes when they begin, and they increase regularly by additions to their sides, till finally they become so heavy as to sink. In other cases, if the brine is boiled away too rapidly, a mass of salt may be formed at the bottom of the vessel, in which no regular crystals (cubes) can be seen. Yet it is obvious that the same power of crystal. lization was at work, and failed of yielding symmetrical solids, because of the rapidity of the evaporation. Crystals of salt have been found in the beds of this mineral a foot or more in breadth, which had been formed by natural evapo. ration; and the whole bed is in all cases crystalline in the structure of the salt. However finely the salt may be ground Explain the terms crystal and crystallization. Are solidification and crystallization the same process? Explain the different results of crystallizatf n by the example of salt. Is every grain, however minute, crystalline 20 STRUCTURE OF MINERALS. up, as that for our tables, still the grains were crystalline in their origin and are crystalline in structure. This subject may be farther illustrated by many other sub. stances. A hot solution of sugar set away to cool, will form crystals upon the bottom, or upon any thread or stick in the vessel; and, these crystals will continue increasing till a large part of the sugar has become crystals. It is a common and' instructive experiment to place a delicate frame. work of a basket or some other object, in a solution of sugar or alum; after a while it becomes a basket of finished gems, the crystals glistening with their many polished facets. Again, if a quantity of sulphur be melted, it will crystallize on cooling. To obtain distinct crystals, the surface crust should be broken as soon as formed, and the liquid part within be poured out; the cavity, when cold, will be found to be studded with delicate needles. The crust in this case is as truly crystallized as the needles, although but faint traces of a crystalline texture are apparent on breaking it. This was owing to too rapid cooling. Melted lead and bis. muth will crystallize in the same manner. There is a sub. stance, iodine, which when heated passes into the state of a vapor; on cooling again, the glass vessel containing the vapor is covered with complex crystals, as brilliant as pol. ished steel. During the cold of winter, the vapors constituting clouds, often become changed to snow; this is a similar process of crystallization, for every flake of snow is a congeries of crystals, and often they present the forms of regular six-sided stars. So also, our streams become covered with, ice; and this is another form of the crystallization of water. The power which solidifies, and the power which crystal. lizes, are thus one and the same. Crystallography, there. fore, is not merely a science treating of certain regular solids in Mineralogy; it is the science of solidification in general. Modes of Crystallization. In the above examples we have presented three different modes of crystallization. In one case, the substance is in solution in water, (or some sol. vent;) the particles are thus free to move, and as the solvent passes off by evaporation, they unite and form the crystal. Explain the case of sulphur. Give instances of crystals forming from vapor. What does the science of crystallography embrace? What are the modes of cryrtallization alluded to in the examples given? CRYSTALLOGRAPHY. 21 lizing solid. In a second case, the substance is fused by heat; here again the particles are free to move as long as the heat remains; and when it passes off solidification commences, under the power of crystallization. In a third case, the substance is reduced to a vapor by heat; and from this state-also one of freedom of motion among the particlesit crystallizes as the heated condition is removed. In the hardening of steel, it is well known that the coarse. ness of the grains varies with the temperature used, and the manner in which the process is conducted. An increased coarseness of structure, implies that certain of the crystal. line grains were enlarged at the expense of -others. It teaches us that in some cases the powers of crystallization may act at certain temperatures, even without fusion or solution. The long continued vibration of iron, especially when under pressure, produces a similar change from a fine to a coarse texture; and this fact has been the cause of ac. cidents in machinery, by rendering the iron brittle: it has led to the fracture of the axles of rail cars and of grindstones, and even the iron rails of a road may thus become weak and useless. By these several processes, the various minerals and very many of the widely extended rocks of our globe, have been brought to their present state. Perfect crystals are usually of moderate size, and gems of the finest water are quite small. As they enlarge they become less clear, or even opaque, and the faces lose their smoothness and much of their luster. The emerald, sufficiently pure for jewelry, seldom exceeds an inch in length, and is rarely as large as this; but a crystal of this species (of the variety beryl) was obtained a few years since at Acworth, New Hampshire, which measured 4 feet in length and 2 feet in circumference; it was regular in its form, yet, except at the edges, opaque. The clear garnets, fit for set. ting, are seldom half an inch through; but coarse crystals have been found 6 inches in diameter. Transparent sap. phires also, over an inch in length, are of extreme rarity; but opaque crystals occur a foot or more long. Quartz crystals attain at times extraordinary dimensions. There is one at Milan which is 3~ feet long and 5~ in circumference, and it weighs 870 pounds. From a single cavIs fluidity essential to the process of crystallization? What is said of steel and iron? What is said of the size and perfection of crystals? 22 STRUCTURE OF MINERALS. ity at Zinken, in Germany, 1000 cwt. of crystals of quartz were taken above a century since. These facts indicate imperfectly the scale of operations in the laboratory of nature. The same process by which a single group, like that just alluded to, has been formed, has filled numberless similar cavities over various regions, and distributed the quartz material through vast deposits in the earth's structure. The same power presides alike over the solidification of liquid lavas, and the formation of a cube of salt, producing the crystalline grains constituting the former, and the structure and symmetrical faces of the latter. Constancy of Crystalline Forms. Each mineral may be properly said to have as much a distinct shape of its own, as each plant or each animal, and may be as readily distinguished by the characters presented to the eye. Crystals are, therefore, the perfect individuals of the mineral kingdom. The mineral quartz has a specific form and structure, as much as a dog, or an elm, and is as distinct and unvarying as regards essential characters, although, owing to counteracting causes during formation, these forms are not always assumed. In whatever part of the world crystals of quartz may be collected, they are fundamentally identical. Not an angle will be found to differ from those of crystals obtained in any part of this country. The sizes of the faces vary, and also the number of faces, according to certain simple laws hereafter to be explained; but the corresponding angles of inclination are essentially the same, whatever the variations or distortions. Other minerals have a like constancy in their crystals, and each has some peculiarity, some difference of angle, or some difference of cleavage structure, which distinguishes it from every other mineral. In many cases, therefore, we have only to measure an angle to determine the species. Both quartz and carbonate of lime crystallize at times in similar six-sided prisms with terminal pyramids; but the likeness here ceases; for the angles of the pyramids are quite different, and also the internal structure. Idocrase and tin ore crystallize in similar square prisms, with terminal pyramidal planes; but though similar in general form, each has its own characteristic angles of inclination between its planes, which angles What is said of the generality of the power of crystallization? What is said of the constancy of the crystalline forins and structure of minerals? Explain by the mineral quartz, as an example. CRYSTALLOGRIAPIIY. 23 admit of no essential variation. Upon this character, the constancy of crystalline forms, depends the importance of crystallography to the mineralogist. FUJNDAIENTAL FORMS OF CRYSTALS. The forms of crystallized minerals are very various. To the eye there often seems to be no relation between different crystals of the same mineral. Yet it is true that all the various shapes are modifications according to simple laws of a few fundamental fobrms. There is perhaps no mineral which presents a greater variety of form than calc spar. Dog-tooth spar is one of its forms; nail-head spar, as it is sometimes called, is another; the one, a tapering pyrimadal' crystal, well described in its name, the other broad and thin, and shaped much like the head of a wrought-nail. Yet both of these crystals and many others are derived from the same fundamental form. After a few trials with a knife, the student will find that slices' may be readily chipped off from the crystals of this mineral in three directions; and the process will obtain a solid from each, the one identical with the other in its angles. They consequently have the same nucleus or fundamental form. The fundamental forms are those from which all the other forms of crystals are derived. The derivative forms, are called secondary forms, and their planes, secondary planes. The number of fundamental forms indicated by cleavage, is thirteen. They are either prisms,* octahedrons or dodecahedronzs. The prisms are either four-sided or six-sided. The prisms are denominated right prisms, when they stand erect, and,oblique prisms, when they are inclined. Figures 4, 5, 7, 8, are right prisms, and figures 12, 14, are oblique prisms. The sides in each case are called lateral planes, and the extremities bases. An octahedront has eight sides, and consists of two equal How do the crystals of different minerals differ? Mention examples. What is said of the forms of crystals of the same mineral? What is understood by fundamental forms? What by secondary forms or planes? How many fundamental forms are there? What kinds of prisms are there? Explain the terms lateral planes and bases. * Any column, however many sides it may have, is called a prism. t From the Greek okto, eight, and hedra, face. 24'STRUCTURE OF MIINEn1ALS. four-sided pyramids placed base to base. (Figs. 2, 6, 9 ) The plane in which the pyramids meet is called the base of the octahedron; (bb, fig. 6;) the edges of the base are called the basal edges, and the other edges the pyramidal. The dodecahedron* has twelve sides (fig. 3.) The axes of these solids are imaginary lines connecting the centers of opposite fices, of opposite edges, or of opposite angles. The inclination of two planes upon one another is called an interfacial angle.t The figures here added represent the forms of the bases and faces referred to in the following paragraphs. A B C D E F A, a square, having the 4 sides equal; B, a rectangle, differing from A, in having only the opposite sides equal; C, a rhomb, having the angles oblique and thesides equal; D, a rhomboid, differing from the rhomb in the opposite sides only being equal; E, an equilateral triangle, having all the sides equal; F, an isosceles triangle, having two sides equal. The lines crossing from one angle to an opposite are called diagonals. The fundamental forms of crystals, though thirteen in number, constitute but six systems of crystallization, as follows:What is an octahedron? What is its base? How are the basal and pyramidal edges distinguished? What is a dodecahedron? What are axes? What are interfacialangles? Explain the terms square; rectangle; rhomb; rhomboid; equilateral triangle; isosceles triangle; diagonal. How many systems of crystallization are there? * From the Greek dodeka, twelve, and hedra, face. t An angle is the amount of divergence of two straight lines from a given point, or of two planes from a given edge. In the annexed figure, D ACB is an angle formed by the divergence of two A lines from C. If a circle be described with the angular point C as the center, and the circumference C )B DABFE be divided into 360 equal parts, the number of these parts included between A and B will be the number of degrees in the angle ACB; that is, if 40 of these parts are included between A and B, the lF' angle ACB equals 40 degrees (400). DF being perpendicular to EB, these two lines divide the whole into 4 equal parts, and consequently the angle DCB equals 3600~-4 equals 900. This is termed a right angle. An angle more or less than 90~ is called an oblique angle; if less, as ACB, an acute angle; if more, as ACE, an obtuse angle. PUNDAMIENTAL FORMS OF CRYSTALS. 25 I. The first system includes the cube (fig. I or la, the lat. ter in outline;) regular octahedron (fig. 2;) and the rhombic 1 1~ 2 3 r3a dodecahedron (fig. 3 or 3a.) They are symmetrical solids throughout, in all positions, being alike in having the height, breadth and thickness equal; their three axes, represented by the dotted lines in the figures, are at right angles with one another and.equal. In the cube, the axes connect the centers of opposite faces; in the octahedron and dodecahedron, they connect the apices of solid angles. This is more fully explained on a following page. The cube has its faces equal squares, and its angles all right angles. The octahedron has its 8 faces equal equilateral triangles: its edges are equal; its plane angles are 60~; its interfacial angles (angles between adjacent faces) 1090 28'. The dodecahedron has its 12 faces equal rhombs; the edges are equal; the plane angles of the faces are 109~ 28' and 70~ 32'; its interfacial angles are 120~. II. The second system includes the right square prism 4 5 6 MI M 6 b (figs. 4 and 5,) and square octahedron (fig. 6.) They have two equal lateral axes, and a vertical axis unequal to the What forms does the first system include? How are these forms related? Describe the forms. What forms does the second system include, eLnd how are they related? Describe the forms. In 126. STRUCTURE OF MITNERALS. lateral: that is, the width and breadth are equal, but the height is varying. All the axes are at right angles with one another. Fig. 4 is a square prism higher than its breadth, and fig. 5 is one shorter than its breadth. The right square prism and square octahedron may be of any height, either greater or less than the breadth; but the dimensions are fundamentally constant for the same mineral species. The square prism has its base a square. The square octahedron has its base (bb) a square, and its 8 faces equal isosceles triangles. The lateral edges of the prism differ in length from the basal; and the terminal or pyramidal edges of the octahedron differ in length from the basal. III. The third system includes the rectangular prism (fig. 7,) the rhombic prism (fig. 8,) and the rhombic octahe7 8 9 dron (fig. 9.) They are similar in having the three dimen. sions, or the three axes, unequal; and the axes at right an.t gles with one another. The rectangular prism has a rectangular base, and the axes connect the centers of opposite faces. The rhombic prism and rhombic octahedron have each a rhombic base, the angle of which differs for different species. The lateral axes of the prism connect the centers of opposite edges, and in the octahedron they connect the apices of opposite angles. IV. Thefourth system includes the right rhcmboidal prism 10 11 12 13 (figs. 10, 11,) and the oblique rhombic prism (figs. 12, 13.) The lateral axes are unequal, and at right angles as in the What forms are included in the third system and how are they related? Describe the forms. What forms does the fourth system include and how are they related 1 FUNDAMENTAL FORMS OF CRYSTALS.. 27 last system; but they are oblique to the vertical axes. Their positions are shown in the figures. The right rhomboidal prism stands erect when on its rhom. boidal base, as in fig. 11; but is oblique when placed on either of the other sides, as in fig. 10. The oblique rhombic prism is shown in a lateral view in fig. 12, and a front view in fig. 13. V. Thefifth system includes the oblique rhomboidal prism which has the three axes unequal, 14. 15 and all are oblique in their intersec. tions. Fig. 14 represents a side view of this form, and fig. 15 a / firont view... VI./ The sixth system includes the rhombohedron and hexagonal prism, in which there are 16 16a 17 17a 18 three equal lateral axes and a vertical axis at right angles with the three. Fig. 16 is an obtuse rhombohedron, and 16a is the same in outline, showing the axes. Figs. 17, 17a, represent an acute rhombohedron. Fig. 18 is a hexagonal prism; it is bounded by six equal lateral planes; the lateral axes either connect the centers of opposite faces, as in the figure, or of opposite lateral edges. To understand the rhombohedron, the student should have a model before him. On examining it he will find one solid angle made up of three equal plane angles, and another op. uosite one of the same kind; all the other solid angles are different from these. These two solid angles are called the vertical solid angles, and a line drawn from one to the other is the vertical axis of the rhombohedron. The rhombohe. dron should be held with this line vertical; it is then said to be in position. Thus placed, it will be seen to have six lat. eral angles, six equal lateral edges, and also six equal terminal edges, three of the terminal above and three below. What forms does the fifth system include, and how does this system differ from the preceding? What does the sixth system include? What is said of the rhombohedron? of its position? its solid angles? 28 STRUCTURE OF MINERALS, The lateral edges in figure 17a, are distinguished from the terminal by being made heavier. Figure 19 represents a vertical view of fig. 16; 19 19a the three edges meeting at center are the terminal edges of one ex- tremity: the exterior six are the lateral edges; and the six lateral angles are seen at their intersec. tions. In fig. 19a, the same is seen in outline, and the dotted lines represent the three lateral or transverse axes, connecting the centers of opposite lateral edges. The lateral and terminal edges differ in one set being acute and the other obtuse; in the obtuse rhombo. hedron (fig. 16) the terminals are obtuse, and in the acute rhombohedron (fig. 17) they are acute. Several of the primary forms are easily cut from wood or chalk. Cut out a square stick, and then saw off a piece from one end as long as the breadth of the stick: this is the cube. Saw off other pieces longer or shorter than this, anc they are different right square prisms. Shave off a piece of more or less thickness from one side of the square stick, and it then becomes a rectangular stick. From it, pieces may be sawn off, of different lengths, and they will be right rectangular prisms. Next cut a stick of a rhombic shape, (a section having the shape in figure C, page 26,) from it right rhombic prisms may be cut, of any length. Shave off more or less from one side of the rhombic stick, and it is changed to a rhomboidal form, (section as in fig. D, page 26,) and rhomboidal prisms may be sawn from it of any length. Take a rhombic stick again; and instead of sawing it off straight across, as before, saw off the end obliquely from one side-edge to the opposite; the base thus formed is oblique to the sides: then saw the stick again in parallel oblique di. rections, (accurately parallel,) and an oblique rhombic prism will be obtained. If the oblique direction is such that the basal plane equals the lateral, the solid is a rhombohedron. Proceeding in the same way with a rhomboidal stick, oblique rhomboidal prisms may be made. The student is advised to make these solids, either from wood, raw potatoes, or chalk,* in order to become familiar with them. What is said of the lateral edges and angles of the rhombohedron? Models made of chalk become quite hard if washed over with a strong solution of gum Arabic, or varnish. FUNDAMENTAL FORM3S OF CRYSTALS. 29 By means of such models, the student may trace out im-. portant relations between the fundamental forms. Take a cube, and cut off each angle evenly, inclining the knife alike to the adjacent faces; this produces figure 20. Continue taking slice after slice equally fiom each angle, and the solid takes the form in fig. 20a, (called a cubo-octahedron;) still continue taking off regular slices from each angle alike, and it finally comes out a regular octahedron, the form represented in fig. 20b. The last diminishing point in each 20 20a 20b P P face of the cube is the apex of each solid angle of the octa. hedron. It is hence apparent why the axes of the cube connect the opposite solid angles of the octahedron. Take another cube (one of large size is preferable) and pursue the same process with each of the edges, keeping the knife, in cutting, equally inclined to the faces of the cube, and we obtain, in succession, the forms represented in figs. 21 521a 2lb 21 and 21a; and finally as the plane P disappears, it comes out the rhombic dodecahedron, (fig. 21b.) Hence the same axes which connect the centers of opposite faces in the cube, connect opposite acute solid angles in the dodecahedron. So the cube, by reversing the process, may be made from an octahedron by cutting off its solid angles, passing in succession through the forms represented in figures 20b, 20a, 20, to figure 1. The dodecahedron also yields a cube in a similar manner, giving as the process goes on, the forms rep. resented in figures 21b, 21a; 21, 1. Moreover, the octahedron and dodecahedron are easily de. How can you make an octahedron from a cube? How make a dodecahedron from a cube? How the cube from an octahedron? the cube from a dodecahedron? What relation hence exists between the solids of the first system? 3* 30 STRUCTURE OF MfINERALS. rived from one another. Figure 22 represents an octahedron 22 22a with the edges truncated. On continuing this truncation, the //.A o planes A are reduced in size, A and the form in figure 22a is B\&~ R E obtained; and another step beyond, we have the dodecahedron, (fig. 21b.) Figure 22a represents a dodecahedron with the obtuse solid angles replaced; and this replacement continued, produces finally an octahedron, the reverse of the preceding. These solids are, then, so related that they are all derivable from one another; and the three actually are often presented by the same mineral. All the figures above referred to, occur as forms of galena, fluor-spar, and several other species. Instead, therefore, of considering the three solids, the cube, regular octahedron, and dodecahedron, as independent forms,'we properly speak of them as constituting together one system, or as belonging to the same series of forms. Again: pursue the same mode of dissection on the angles of a square prism, taking care to move the knife parallel to a 23 23a diagonal of the prism; the form in P t figure 23 is first obtained, and finalt a A \A ly a square octahedron, figure 23a. IM X r I b b The square prism and square octaI / 5A hedron (like the cube and regular octahedron) belong to one and the same system. The two often occur in the same mine al. Again: remove with a knife the basal edges of a rhombic 24 24a prism, moving the knife parallel to a diagonal plane of the piism, figure 24 is at first obtained, and then a rhombic AM M:. octahedron, (fig. 24a.) Remove the A\''A four lateral edges of a rhombic prism, (see fig. 26a,) keeping the knife paral. lel to a vertical diagonal plane: the form in figure 25 will first be obtained, and then a right rectangular prism, (fig. 25a); and conversely cut off the lateral edges How can you make a square octahedron from a square prism? How a rhombic octahedron from a rhombic prism? How a rectangular prism from a rhombic? FUNDAMENTAL FORaIS OF; CRYSTALS. 31 a right rectangular prismi with the knife parallel to the ver. 25 25a 26 P'~.i T 26a tical diagonal planes of this prism, 26b {(as is seen in fig, 26,) and a right. i rhombic prism (fig. 26a) is the result. The relations of these two MJ'q6 prisms is shown in figure 26b,.. which represents a rhombic prism within a rectangular prism. It is obvious on comparing these figures, that the lateral axes which connect the centers of opposite faces in the rectangular prism, connect the centers of opposite lateral edges in the rhombic prism. These three forms, the right rhombic prism, rhombic octahedron, and rectangular prism, are so closely related, that one may give origin to the other, and all may occur in the same minerals This is often the case, as in the minerals celestine and heavy spar.: Again: set the right rhomboidal prism on one of its lateral faces, and then slice off each lateral edge, (lateral, as so situated,) keeping the knife parallel with the diago- 27 Cnal plane, and an oblique rhombic prism is obtained. Figure 27 represents the process begun, and figure 13, as well as the interior of figure 27, the completed oblique rhombic prism. Lastly: take a rhombohedron, and after placing it in position, fig. 16,) look down upon it from above, (fig. 19;) the six lateral edges are seen to form a regular six-sided figure around the axis. If these edges be cut off parallel lo the axis, a six-sided prism (having a three-sided pyramid at each extremity) must, therefore, result. This pro. cess is shown begun in figure 28, and completed in figure How is a rhombic prism derived from a rectangular? What relation hence between these prisms? How can yen make an oblique rhombic prism from a right rhomboidal? How a right rhomboidal from an oblique rhombic? Explain the relation betw. en the rhombohedron and hexagonal prism, and how one is reduced to he other. ~3~2 STRUCTURE OF MIN'ERALS. 28a. Looking down again on the model as before, the lat. eral angles are seen to formn six equi-distant points around the axis; and if these angles are removed in the same manner, another six-sided prism is obtained, differing, however9 from the former in having the faces of the pyramid at each end, five-sided, instead of rhombic. Figures 29, 30, illustrate the process. Conversely, we may make a rhombohedron out of 28 28a 29 30 31 R a hexagonal prism, by cutting off three alternate basal edges at one extremity of the prism, and similarly, three at the other extremity alternate with these, as in figure 31. In figure 30, the process is farther continued, and the rombohedron is shown as a nucleus to the prism. By cutting off slices parallel with R, the rhombohedron is at last obtained. The close relation of the rhombohedron and hexagonal prism is hence obvious. Calcareous spar has the rhombohedron as its primary, and very often occurs in hexagonal forms. The same is true of quartz and many other species. From the above transformations, the study of which, with the aid of a knife and a few raw potatoes or lumps of chalk, may afford some amusement as well as instruction, the student will understand more fully the six systems of crystallizatioll.* These six systems have received the following names: I. Monometric or tesseral system, (from the Greek monos, one, and metron, measure, alluding to the three axes being equal in length.) Includes the cube, octahedron and dodecahedron, (figs. 1, 2, 3.) 2. Dimetric system, (from dis, two times, and metron, alluding to the vertical axis being unequal to the other two.) Give the names of the systems of crystallization, and mention the forms each includes. * In some text books, the student may read about certain integral forms, the cube, the three-sided pyramid and three-sided prism, from which it is stated all the other forms may be made. The idea of such fobrms has nothing to do with crystallography, or the actual constitution of crystals. CLEAVAGE. 33 Includes the square prism and square octahedron, (figs. 4, 5, 6.) 3. Trimetric system, (from tris, three times, and metron, alluding to the three axes being unequal.) Includes the right rhombic prism, right rectangular prism and rhombic octahedron, (figs. 7, 8, 9.) 4. 2Monoclinate system, (from monos, one, and klino, to incline, one axis being inclined to the other two which are at right angles.) Includes the right rhomboidal prism and oblique rhombic prism, (figs. 10, 11, 12, 13.) 5. Triclinate system, (from tris and klino, the three axes being oblique to one another.) Includes the oblique rhomboidal prism, (figs. 14, 15.) 6. Hexagonal system. Includes the rhombohedron and hexagonal prism, (figs. 16, 17, 18.) CLEAVAGE. It has already been stated that crystals of calcareous spar may be chipped off easily in three directions, and by this means, the fundamental form, a rhombohedron, may be obtained. In all other directions only an irregular fracture takes place. This property of separating into natural layers, is called cleavage, and the planes along which it takes place, cleavage joints. Cubes of fluor spar may be cleaved on the angles, with a slight pressure of the knife, and the process continued affords successively the forms represented in figures 20, 20a, and finally the completed octahedron, as already explained. A lead ore, called galena, yields cubes by cleavage. Micaoften improperly called isinglass-may be torn by the fingers into elastic leaves more delicate than the thinnest paper. In many species cleavage is obtained with difficulty, and in others none can be detected. Quartz is an instance of the latter; yet it may sometimes be effected with this mineral by heating it and plunging it while hot into cold water. The following are the more important laws with respect to this property: Cleavage is uniform in all varieties of the same mineral. It occurs parallel to the faces of a fundamental form or along the diagonals. It is always the same in character parallel to sinmi7lar faces What is cleavage? How does it differ in different minerals? What are the laws relating to cleavage. 34 STRUCTURE OF MINERALS. of a crystal, being obtained with equal ease, and affording planes of like luster: and conversely, it is dissimilar paral. lel to dissimilar planes. It is accordingly the same, parallel to all the faces of a cube; but in the square prism, the basal cleavage differs from the lateral, because the base is unequal to the lateral planes. Often there is an easy cleavage parallel to the base, and none distinct parallel to the sides, as in topaz; and so the reverse may be true. The thirteen fundamental forms enumerated, are the solids obtained from the various minerals by cleavage. Some minerals present peculiar cleavages of a subordinate character, independent of the principal cleavage. Cale spar, for example, has sometimes a cleavage parallel to the longer diagonal of its faces. The facts on this subject are of con. siderable interest, yet not of sufficient importance to be dwelt on in this place. SECONDARY FORMS. If crystals always assumed the shape of the primary form, there would be comparatively little of that variety and beauty which we actually find in the mineral kingdom. Nature first taught to heighten the brilliancy of the gem by covering its surface with facets. To the uninstructed eye, these cubes and prisms with their numberless brilliant surfaces, often appear as if they had been cut and polished by the lapidary: yet the skill and finish of the work, most perfect in the microscopic crystal, has but feeble imitation in art. Not unfrequently, crystals are found with one or two hundred dis. tinct planes, and occasionally even a much larger number; and every edge and angle; has the utmost perfection, and the surfaces an evenness of polish, that betrays no rude workmanship, even under the highest magnifying glass. Cavities are occasionally met with in the rocks, studded on every side with crystals-a crystal grotto in minature-sparkling when brought out to the sun like a casket of jewels. Even amid the apparent confusion, there is wonderful order of arrangement in the crystals: the corresponding planes generally face the same way, so that the sparkling effect appears in successive flashes over the surface, as every new set of facets comes in turn to the light. Add to this view, their delicate colors-the rich purple of the amethyst, the soft yellowish shades of the topaz, the deep green of the eme. On what does the beauty of crystals to a great extent depend? MODIFICATIONS OF CRYSTALS. 35 raid-and it will be admitted that the powers of crystallization scarcely yield to vitality in the forms of beauty they produce. These results are not more wonderful than the simplicity of the laws that lead to them. The various secondary forms proceed from the occurrence of planes on the angles or edges of the fundamental forms, which planes are called secondary planes. Figures 20, 21, are secondaries to the cube, and the planes a and e are secondary planes; figures 28, 29, 30, are secondaries to the rhombohedron, and the planes e and a are secondary planes.* These secondary planes however numerous, con. form in their positions to a certain law called the law of symmetry. Previous to stating this law a few explanations are added. The cube, it has been remarked, has six equal square faces. The twelve edges are therefore all equal, and so also the eight angles. In the square prism the vertical edges difer in length from the basal, and are therefore not similar. In the rectangular prism, not only the vertical differ from the basal, but two of the basal at each extremity differ from the other two basal. This will be seen at once in the models. In the right rhombic and rhomboidal, two of the lateral edges are acute and two obtuse; these then are not similar to one another. In the oblique prisms some of the basal edges are acute and some obtuse. After tracing out the similar and dissimilar angles and edges in the primaries, with the models, the following laws may be easily applied: Either1. All the similar parts of a crystal are similarly and simultaneously modified;* or,Explain the relation of secondary planes to the fundamental form. What is said of the cube? of the square prism? the rectangular prism? the right rhombic and rhomboidal? the oblique prisms? What is the first law repecting secondary planes? Note.-What is meant by replacement, bevelment, and truncation? * To avoid circumlocutions, the following technical terms are employed in describing the modifications of crystals. Replacement. An edge or angle is replaced, when cut off by one or more secondary planes, (figs. 20, 21, 32.) Truncation. An edge or angle is truncated, when the replacing plane is equally inclined to the adjacent faces, (figs. 20, 21.) Bevelment. An edge is beveled, when replaced by two planes, which are respectively inclined at equal angles to the adjacent faces, (fig. 32.) Truncation and bevelment can occur only on edges formed by the meeting of equal planes. 36 STRUCTURE OF MINERALS. 2. Half the similar parts of a crystal, alternate in position, are modified independently of the other half. In the cube, octahedron, or dodecahedron, if one edge is replaced, all the other edges will be replaced, and by the same planes. If there are two planes on one edge, (fig. 32) there will be two on every other edge; and the two on each will have the same inclinations. If there are three planes on one angle, (fig. 33) there will, in the same manner, be three on the other seven angles. Perfect symmetry is thus preserved, however numerous the added planes. The following figures illustrate this principle, that all the edges, and all the angles are modified alike. 32 33 34 35 This symmetry is well seen in the solids which the secondary planes, in the above figures, produce, if enlarged till -he primary planes are obliterated. Thus from figure 32, comes the form in figure 36, the planes e' being enlarged till the planes P are obliterated; from 33, comes the form in fig. 37; from 34, the formn in 38; and from 35, the form in 39. The form in figure 37 has 24 faces, and is called a trapezohedron. It is common in garnet and leucite. 36 37 38 39 In figure 35, there are six planes on each angle, and as there are eight angles in the cube, the solid represented in figure 39 has forty-eight faces. Both 38 and 39 are forms of the diamond. In connection with the law above given, it is stated that half the similar parts may be modified independently of the other half. The parts thus modified are alternate with one another and still produce symmetrical solids. Thus the What second law is mentioned? Explain the first law ty examples. MODIF'ICATIONS OF CRYSTALS. 37 cube may have only the alternate angles replaced; or only one of the two beveling planes shown in figure 32 may occur on each edge; or three of the six on each angle in figure 35. The following are examples; and each figure in the lower line, represents the completed form, produced by extending the secondary planes in the figure above, to the obliteration of the primaries, as explained on the preceding pages. 40 41 42 43 aY P P p P fP 44 45 46 47 The replacement begun in figure 40, continued to the obliteration of the Ps, produces figure 44, which is a tetrahedron, or three-sided pyramid. So the planes a' in figure 41, give rise to fig. 45; the planes e in 42, to figure 46, which is a pentagonal dodecahedron, so called because it has twelve pentagonal (or five-sided) faces. The forms represented in figures 40 and 41 are common in boracite, and those of figures 42, 43, in iron-pyrites. These forms with half the full num. ber of planes are called hemihedrdl forms, from the Greek words for half and face. The tetrahedron is sometimes placed among the primary forms; but it is properly a secondary form, derived from the cube, in the manner here explained, or from the octahedron by the extension of four faces to the obliteration of the other four. (Compare figs. 2 and 44.) In the right square prism, the basal edges being unequal to the vertical, (because the prism, unlike the cube, is higher than broad,) these two kinds of edges are not replaced by similar planes, and the basal may be modified when the lateral are not modified, (figs. 48, 49.) The lateral edges may be truncated, because their including planes are equal; Explain the second law. What are the resulting forms called? What is said of the tetrahedron? 4 38 STRUCTURE OF MINERALS. the terminal cannot be truncated, but are replaced by planes unequally inclined to the including planes. The solid angles 48 49 50 of the square prism are of one kind and are replaced alike, as in figures 23, 50; all the angles in these figures have the same number of planes, and the two adjacent planes in figure 50 are similar in their inclinations, because the lateral planes M, M, of a square prism, are equal. In the rectangular and rhombic prisms the lateral axes are unequal. Consequently in the: rectangular prism, two basal edges differ from the other two, and are therefore modi. fled independently (figs. 51, 52.) The planes 6 extended to the obliteration of T and P, would produce a rhombic prism (in a horizontal position,) as shown in figure 53, and another horizontal prism may be formed by the extension of the planes E, fig. 52. In the rhombic prism the basal edges cor51 52 53 54 l5 Cre t t l.....s..l \ \/ /r? 55 respond to the angles of the rectangular prism,<-i3 (see fig. 26b) and are similar and simultaneously replaced as in figure 24. The basal angles are X le eI M unlike, one being obtuse and the other acute, and the planes of the two (fig. 54) differ in their in. clinations. The lateral edges differ in the same manner, two being obtuse and two acute, and they are inde. pendently replaced, as in figure 55. The two planes e are similar planes, because, in a rhombic prism, M and M are equal; and the extension of these planes may produce another rhombic prism. In an oblique rhombic prism the superior basal edges dif. Explain these laws from the square prism; the, rectangular and rhombic. MODIFICATIONS OF CRYSTALS, 39 fer fiom the inferior in front, two being obtuse and two acute; consequently, they are independently replaced. Figure 56, shows the replacement of the obtuse basal. So also the fiont angles differ in the same manner, the upper (left side in fig. 57) being independent of the inferior in its modifications. 56 57 58 59 But the four lateral angles are similar (fig. 58.) Two of the lateral edges are obtuse and two acute, as in the right rhombic prism, and their secondary planes are therefore unlike (fig. 59.) 60 In the oblique rhomboidal prism, 61 P only two diagonally opposite edges ~/ o / / or angles are similar, and the modi- a l M T/ fications of one edge are therefore MT / —-./ independent of those of all the other edges, except the one diagonally.1 opposite: the same is true of the angles. The difference between this prism and the oblique rhombic will thus be seen on comparing figures 56 and 60, and also figures 58 and 61: In the rhombohedron, the distinction of vertical and lateral solid angles has already been explained, and also the differ. ence between the terminal and lateral edges. The figures given will show how these distinctions are carried out in the 62 63 64 65 modifications. In figure 62, the terminal solid angles are replaced, but none of the lateral. In figures 64, 65 and 29, the lateral angles are replaced, but not the terminal. Figure 63, has the terminal edges replaced, and figures 68 and 28. the lateral edges. Explain the laws with regard to secondary planes from the oblique rhombic prism; oblique rhomboidal; the rhombohedron. 40 STRUCTURE OF MINERALS. When the planes a' in figure 64 are a little more extended, the form is changed to figure 65, or a double six-sided pyramid. It is in this way that the pyramidal form of crystals of quartz is produced from the primary rhombohedron. In figure 66, 66 67 68 69 e e a', as is seen, is a different plane from a" in figure 64. By enlarging the planes a', till the planes R are obliterated, figure 67 is obtained, an acute rhombohedron. This may appear a singular result: but it will be understood on considering that there are six lateral angles; and three of the planes a' incline upward, and three, alternate, incline downward; they must therefore produce an oblong solid, bounded by six equal faces, which is nothing else than a rhombohedron. In figure 68, the lateral edges are beveled by the planes e'. The planes e' enlarged to the obliteration of the faces R, lead to the form in figure 69-a twelve-sided figure, or dodecahedron, and called from the shape of its faces, a scalene dodecahedron.' It is the form of dog-tooth spar, a variety of calcareous spar. In figures 28, 29, the planes e and a are each parallel to the vertical axis, and they consequently produce prisms when extended, as explained on pages 31, 32. In figure 3, under Tourmaline, we have an instance of a hemihedral modification in the hexagonal system. The ex. tremities of the prism, as will be observed, have different secondary planes, there being in addition to the three faces R, three small triangular planes above, and three narrow linear planes below. Topaz crystals are also differently modified at the extremities, and are examples of hemihedral modifications in a right rhombic prism. Another law gives still greater interest to the study of crystallography: but it can only be briefly alluded to in this place. When speaking of the right square prism it was Mention some instances of hemihedral modifications, and explain. MODIFICATIONS OF CRYSTALS. 41 stated that the basal edges were never truncated, but, when modified, were replaced by planes unequally inclined to the basal and lateral faces of the primary. These secondary planes do not however occur at random, at any possible inclination; but there is a direct relation, in all instances, to the comparative height and breadth of the fundamental form of the mineral. The same is true of planes on the angles, and' in secondaries to all the fundamental forms. Take a cube and cut off evenly one of the edges: this removes parts of two other edges, at each end of the plane. It is found that in cubic crystals these parts are either equal to one another, or one is double of the other, or treble; or in some. other simple ratio. The same is true in the other fundamental forms, except that, as stated, the relative height and breadth of the prism come into account, and influence the result. For example: in figure 70, 70 71 (a section of a cube,) P M and P 7.C. I, b c X P N are equal edges, divided into equal parts; now a plane a ]/ a on an edge of a cube, as a b,/ removes, as is seen, equal parts d of P M and P N; another, as _ a c, removes twice as many parts of one edge as of the other; and so other planes have like simple ratios. In figure 71, a section of a prism, the lines P M and P N (height and breadth of the prism) are unequal: let them be divided into a like number of parts; then a plane on an edge, as a b, will cut off as many parts of P M as of P N; others, as a c, b d, twice as many parts of one as the other: and so on. a b truncates the edge in figure 70; but not so in figure 71. It is evident to the mathematical scholar that the inclination of a plane a b to P N or P M, is sufficient to determine the relative dimensions of P a and P b, or the relative height and breadth of the fundamental form. These principles give a mathematical basis to the science. Thus we perceive that the attraction which guides each particle to its place in crystallization, produces forms of Mathematical exactness. It covers the crystal with scores Df facets of finished brilliancy and perfection; and these What other law is there, respecting the occurrence of secondary planes? Explain by the figures. 4* 42 STRUCTURE OF IINERALS. facets are not only uniform in number on similar parts of a crystal, but are even fixed in every angle and every edge.* COMPOUND CRYSTALS. In the preceding pages, we have been considering simple crystals, and their secondary forms. The same forms are occasionally compounded so as to make what have been called twin or compound crystals. They will be understood 72 73 74 75 at once from the annexed figures. Figure 72 represents a crystal of snow of not unfrequent occurrence. It consists, as What is a twin or compound crystal? * On a preceding page, it has been explained that in monometric cystals the axes are equal; in dimetric and hexagonal crystals the lateral axes are equal, and the vertical is of a different length, shorter or longer. In the other systems, the trimetric and the two oblique systems, the three axes are all unequal. In the above paragraphs it has been shown that the relative lengths of the axes in a fundamental form of a crystal are fixed, and may be determined by simple calculations. These fixed relative dimensions are supposed to be the relative dimensions of the particles or molecules constituting crystals; that is if the fundamental form of a crystal is twice as long as broad, the same is true of its molecules. The molecules of a cube must therefore be equal in different directions; those of a square prism must be longer or shorter than broad, but equal in breadth and thicknesss; those of a rectangular prism 1 2 2a 3 must be unequal in three directions; and the relative a a (4 ~ /fl M inequality is determinable as,...L.. I just stated. The simplest and 3a most probable view of the forms of molecules is that they are spheres for monometric solids; and ellipsoids of different axes for the other forms.; Figure 1 represents a sphere. Figure 2 represents an ellipsoid with the lateral axes equal, as seen in the cross section 2a; it is the form in the dimetric and hexagonal systems. Figure 3 represents an ellipsoid with the lateral axes unequal (fig. 3a), as in the trimetric and oblique systems; a variation in the length of the axes will vary the dimensions, according to any particular case. COnMPOJND LRYSTALS. 43 is evlident to the eye, either of six crystals meeting in a point, or of three crystals crossing one another. Besides, there are numerous minute crystals regularly arranged along the rays. Figure 73 represents a cross (cruciform) crystal of staurotide, which is similarly compound, but made up of fewer crystals. Figure 74, is a compound crystal of gypsum, and figure 75, one of spinel. These will be understood from the following figures. Figure 76 is a simple crystal of gyp- 76 77 sum; if it be bisected along a b, and a the right half be inverted and applied X to the other, it will form figure 74, A which is therefore a twin crystal, in which one half has a reverse position from the other. Figure 77, is a simple octahedron; if it be bisected through the dotted line, and the upper half, after being revolved half way around, be then united to the lower, it produces figure 75. Both of these therefore are similar twins, in which one of the two component parts is reversed in position.* Compound crystals are generally distinguished by their reentering angles. Besides the above, there are also geniculated crystals, as in the annexed figure. The bending has here 78 taken place at equal distances from the center t a of the crystal; and it must therefore have been subsequent in time to the commence- \ ment of tha crystal. The prism began from a simple molecule: but after attaining a certain length, an abrupt change of direction took place. The angle of geniculation is constant in the same mineral species; for the same reason that the angles of secondary planes are fixed; and it is such that a cross section directly through the geniculation is parallel to the position of a common secondary plane. In the figure given, the plane of geniculation is parallel to one of the terminal edges. Mention illustrations. Explain their structure in the case of gypsum and spinel. What is said of geniculated crystals? * Such crystals have proceeded from a compound nucleus in which one of the two particles was reversed. Compound crystals of the kind above described, thus differ from simple crystals in having been formed from a nucleus of two ormore united molecules, instead of from a simple nucleus. 44 STRUCTURE OF IMINERALS. DIMORPHISh-.-POLYMOnRPHISM. It was formerly supposed that the same chemical com. pound could have but a single mode of crystallization. But later researches have discovered that there are many instances of substances crystallizing according to two distinct systems. Thus sulphur at different times crystallizes in ob. lique prisms and right rhombic octahedrons, or according to the two systems monoclinate and trimetric. Carbonate of lime at one time takes on the rhombohedral form, and is then called calc spar; at another, that of a rhombic prism, and it is then termed arragonite. Again, sulphuret of iron presents us both with cubical (monometric) crystals and rhombic prisms (tximetric.) As far as investigation has gone, it has appeared that one of these forms is assumed at a lower temperature than the other; and this takes place uniformly, so that the temperature attending solidification, in certain cases at least, determines the forms and system of crystal. lization. How far other causes operate is unknown. This property is termed dimorphism, (from the Greek dis, two or twice, and morphe, form,) and a substance presenting two systems of crystallization is said to be dimorphous. In addition to the above, garnet and idocrase, the one dodeca. hedral, and the other square-prismatic, are different forms of the same substance. Rutile, which is dimetric, anatase, dimetric also, but of different dimensions, and Brookite, which is trimetric, are three distinct forms of the same substance, oxyd of titanium. In this last case, the property has been called trimorphism, (firom the Greek tris, three times, and morphe, form.) As the number of forms may be still greater, the more general term polymorphism (polus, many, and morphe) has been introduced to include all cases, whatever the number of forms assumed. A polymorphous substance in its different states presents not merely difference of form. There is also a difference in hardness, specific gravity and luster, in fact, in nearly all physical qualities. Arragonite has the specific gravity 2'93, and, calc spar only 2'7; the hardness of arragonite is 3~, and that of calc spar but 3. May the same substance crystallize under more than one fundamental form? Mention examples. What is this property called? What is said of oxyd of Titanium? What is trimorphism? polymorphism? What other differences beside that of form are connected with polymorphism? IRREGULARITIES OF CRYSTALS. 45 The forms of a dimorphous substance differ in stability. Arragonite when heated gently falls to powder, arising fiom a change in the condition of its particles. Arragonite has been obtained by evaporating a solution of lime over a water bath, and calc spar when the same was evaporated at the ordinary temperature. When a right rhombic prism of sulphate of zinc (which is dimorphous) is heated to 1260 F. certain points in its surface become opaque, and from these points, bunches of crystals shoot forth in the interior of the specimen; and in a short time the whole is converted into. an aggregate of these crystals, diverging from several centers on the surface of the original crystal. These small crystals are oblique rhombic prisms; and the same form may be ob. tained by evaporating a solution at this temperature or above it. Many other similar cases might be cited, but these serve to explain the principle in view. IRREGULARITIES OF CRYSTALS. Before concluding this subject, a few remarks may be added on the irregularities of crystals. Crystals of the same form vary much in length, and in the size of corresponding faces. The same mineral may occur in very short prisms, or in long -and slender prisms: and some planes may be so enlarged as to obliterate others; a few figures of quartz crystals will illustrate these peculiarities. 79 80 81 82: 83 Figure 79 is the regular form of the crystal. Figure 80 is the same form with some faces very much enlarged, and others very small. Figure 81 is a very short prism and pyramid of quartz, such as is often seen attached to the surface of rocks; and figure 82 is a similar form very much elongated. Notwithstanding all these variations, every angle What are some of the irregularities o" crystals? 46 STRUCTURE OF MINERtAItS of inclination remains the same: and this is a general fact in all crystals, that whatever distortions take place, the angles are constant. Greater diversity is given to the shapes of crystals by these simple variations, without multiplying the number of distinct forms. Figure 83 is a tapering prism of the same mineral, with a minute pyramid at the apex. The faces of this pyramid have exactly the same inclinations as those of figure 79. The constancy of the angles shows that the fundamental form of the crystal, or, in other words, the form of its mole. cules, is constant, amid all these variations of size and shape. Crystals have sometimes curved faces. The faces of diamonds are usually convex, and some crystals are almost 84 spheres. Figure 84 is one of these diamond crystals. It is the same form as is represented in figure 45. For cutting glass, they always select those crystals that have a natural curved edge, as others are much inferior for the purpose and sooner wear out. In figure 85 a different kind of curvature is represented. It is a curved rhombohe. 85 dron, in which the opposite faces are parallel in their curving: it is a common form of spathic iron and pearl spar. The latter mineral from Lockport, New York, is always curved in this way. Still more singular curvatures are sometimes met with. In the mammoth cave of Kentucky, 86 leaves, vines and flowers are beautifully imitated in alabaster. Some of the "6 rosettes" are a foot in diameter, and consist of curving leaves, clustered in graceful shapes. The frostings on our windows in winter are often miniature pictures of forests and vines with rolled tendrils. It is one among the many singular results of crystallization. On the cool mornings of spring or autumn, in this climate, twigs of plants are occasionally found encircled by fibrous icy curls, (fig. 86,) which are attached vertically to y the stem. They are formed during the night, and disappear soon after the appearance of the sun. What is said of curved crystals? What of curved crystallizations of gypsum? of ice? MEASUREMENT OF CRYSTALS. 47 ON MEASURING ANGLES OF CRYSTALS. As the angles of crystals are constant, minerals, as has been stated, may often be distinguished by measuring these angles. This is done by means of instruments called goni. onzeters, a term meaning, literally, angle-measurers.* These are of two kinds; one is called the common goniometer, the other the reflecting goniometer. The common goniometer depends on the 87 very simple principle that when two straight A lines cross one another, as A E, C D in the \ annexed figure 87, the parts will diverge d equally on opposite sides of the point of intersection (0); that is, in mathematical language, the angle A O D is equal to the angle C O E, and A O C is equal to D O E. The instrument in common use is here represented. 88 -It consists of two arms, a b, c d, moving on a pivot at o: the arms open and shut, and their divergence, or the angle they make with one another, is read off on the graduated are attached. In using it, press up between them, the edge of the crystal whose angle is to be measured, and continue opening the arms thus till the inner edges lie evenly against the faces that include How are the angles of crystals measured.? Explain the principle of the common goniometer from the figure. Explain the common goniometer and its use. * From the Greek gonu, angle, and metron, measure. .48 STRUCTURE OF MINERALS. the required angle. To insure accuracy in this respect, hold the instrument and crystal between the eye and the light, and observe that no light passes between the arm and the applied faces of the crystal. The arms may then be secured in position by tightening the screw at o; the angle will then be measured by the distance on the are from k to the left or outer edge of the arm c d, this edge being in the line of o, the center of motion. As the instrument stands in the figure, it reads 450~. The arms have slits at g h, n p, by which they may be shortened so as to make them more convenient for measuring small crystals. In some instruments of this kindt the arc is detached from the arms. When this is the case, after the measurement is made and the screw at o tightened, the arc (which has the shape of a f b in the annexed figure, except that from a to b is a solid bar) is adjusted to the upper edge of one of the arms, bringing the mark at o, the center, exactly to the center of divergence of the arms. The angle is then read off as before. With a little ingenuity the student may construct a goniometer for himself that will answer a good purpose. A semicircle may be described on mica or a glazed card, of the shape in figure 88: it should then be divided into halves at f, and again each half subdivided into nine equal parts. Each of these parts measures 10 degrees; and if they are next divided into ten equal parts, each of these small divisions will be degrees. The semi-circle may then be cut out, and is ready for use. The arms might also be made of stiff card for temporary use; but mica, bone or metal is better. The arms should have the edges straight and accurately parallel, and be pivoted together. The instrument may be used like that last described, and will give approximate results, sufficiently near for distinguishing most minerals. The ivory rule accompanying boxes of mathematical instruments, having upon it a scale of sines for measuring angles, will answer an excellent purpose, and is as con- 89 venient as the arc. The annexed figure will illustrate the mode of using it. The scale is graduated along the margin, the middle point marking 900, and the divisions either side 10 degrees (as in the figure) and also single de. How is it used when the arms are detached? How may a temporary goniometer be made? How may a scale of sines b4 1sed? MEASUREMENT- OF CRYSTALS. 49 grees. The arms are so applied to the scale, that the center of motion is exactly at the extremity of the middle line, marked 90; and the leg crossing the scale (or that edge of it in the line of the center of motion) will then indicate by its position over the graduated margin, the angle desired.* In making such measurements it is important to remember that1. An angle A 0 D (figure 87) and A 0 C, together, equal 180~; so that if A 0 C be measured, A 0 D is ascertained by subtracting A 0 C from 180~. 2. In a rhomb or rhomboid, b a b and a b a, to- b gether, equal 180~; and one may be ascertained by subtracting the other from 180~. If an obtuse angle of a rhombic prism has been measured and found to be 1100, and the acute angle on measurement is ascertained to be 600, the student should add the two together to find whether the sum is 1800; for if not, there is some error in the measurement, and it should be repeated. 1103 added to 60~ makes 170~, showing in this case an error of 100. 3. In any polygon, the sum of the angles is equal to twice as many right angles as there are sides less two. Let the number of sides, for example, be 6: 6 less two is 4; and the angles together equal twice 4, (or 8,) right angles, which is equivalent to 8 X 90~ =720~. If we have a prism of six sides, and wish to ascertain the angles between these sides, the angles should be measured successively, and the whole added together to ascertain whether the measurements are correct. If the sum is 7200, there is good reason to confide in them. Crystals are at times a little irregular; and this should be looked to, as part of the apparent error may at times be thus accofinted for. This general principle and the What three points must be observed in making measurements? Another mode for approximate results consists in holding the crystal with the two faces (whose inclination is to be measured) in an exactly vertical position over a piece of paper: then place a small rule parallel, as near as the eye can judge, to one face, and draw a line; next do the same for the other face. The angle between the two lines, measured either by an are or the ivory rule just mentioned, is the desired inclination. With practice, much skill mnay be acquired in such trials. They may be made with microscopic crystals under a microscope. 5 50 STRtUC'URE OF MINEiALES. preceding, which is only a simpler case of the same, are of great importance in the measurements of crystals. Reflecting Goniorneter. The reflecting goniometer affords a more accurate method of measuring crystals that have luster, and may be used with those of minute size. The principle on which this instrument is constructed will be understood from the annexed figure (fig. 90) representing a 90 crystal, whose angle a b c is required. d The eye, looking at the face of the' crystal b c, observes a reflected image of m, in the direction P n. On revolving, the crystal till a b has the position of b c, the same image will be seen again in the same direction P n. As the crystal is turned, in this revolution, till a b d has the present position of b c, the angle d b c measures the number of degrees through which it, is revolved. But d b c, subtracted from 180~, equals the angle of the crystal a b c. The crystal is therefore passed in its revolution through a number of degrees, which, subtracted from 1800, give the required angleo This angle, in the reflecting goniometer of Woliaston, is measured by attaching the crystal to a graduated circle which revolves with it, as here represented (fig. 91.) 91 A B is the graduated cirA cle. The wheel, mz, is at. tached to the main axis, and moves the graduated circle 7 together with the adjusted crystal. The wheel, nz, is which passes through the - main axis, (which is hollow for the purpose,) and moves merely the parts to which B the crystal is attached, in order to assist in its adjust. ment. The contrivances for the adjustment of the crystal are at p, q, r, s. To use the instrument, it must be placed on a small stand or a table, and so elevated as to allow the observer to rest his elbows on the table. The whole, thus Explain the principle of the reflecting goniometer. Explain the mode of using the instrument. MEASUREJYIENT OF CRYSTALS. 51 firmly arranged, is to be placed in front of a window, distant firom the same fiom six to twelve feet, and with the axis of the instrument parallel to it. Preparatory to operation, a dark line must be drawn below the window near the floor, parallel to the bars of the window; or, what is better, on a slate or board placed before the observer on the table. The crystal is attached to the movable plate, q, by a piece of wax, and so arranged that the edge of intersection of the two planes forming the required angle, shall be in a line with the axis of the instrument. This is done by varying its situation on the plate, q, or the situation of the plate itself, or by means of the adjacent joints and wheel, r, s, p, as will be readily understood from the instrument. When apparently adjusted, the eye must be brought close to the crystal, nearly in contact with it, and on looking into a face, part of the window will be seen reflected, one bar of which must be selected for the trial. If the crystal is cor. rectly adjusted, the selected bar will appear horizontal, and on turning the wheel, n, till this bar, as reflected, is observed to approach the dark line below, seen in a direct view, it will be found to be parallel to this dark line, and ultimately to coincide with it. If there is not a perfect coincidence, the adjustment must be altered until this coincidence is obtained. Continue then the revolution of the wheel, n, till the same bar is seen by reflection in the next face, and if here there is also a coincidence of the reflected bar with the dark line seen direct, the adjustment is complete; if not, alterations must be made, and the first face again tried. A few successive trials of the faces, will enable one to obtain a perfect adjustment. The circle A B is usually graduated to half degrees, and by means of the vernier, v, minutes are measured. After adjustment, 180~ on the arc must be brought opposite 0, on the vernier. The coincidence of the bar and dark line is then to be obtained, by turning the wheel, n. When obtained, the wheel, m, should be turned until the same coincidence is observed, by means of the next face of the crystal. If a line on the graduated circle now corresponds with 0 on the vernier, the angle is immediately determined? by the number of degrees opposite this line. If no line corresponds with 0, we must-observe which line on the vernier coincides with one on the circle. If it is the 18th on the vernier, and the line on the circle next below 0 on the vernier marks 125~, 52 STRUCTURE OF MINERALS. the required angle is 121' 18'; if this line marks 125' 30'9 the required angle is 1250 48'. Some goniometers are furnished with a small polished reflector, attached to the foot of the instrument below the part s, q, which is placed at an oblique angle so as to reflect a bar of the window. Tile reflected bar then answers the purpose of the line drawn below the window, (or on a slate,) and is more conveniently used. Other modes of adjustment for the crystal, are also used; but they will explain themselves to the student acquainted with the above explanations, and need not here be dwelt upon. MASSIVE MINERALS, OR IMPERFECT CRYSTALLIZATIONS. Massive or imperfectly crystallized minerals either consist of fibers or minute columns, of leaves or laminse, or of grains: in the first, the structure is said to be columnar; in the second, lamellar; in the third, granular. We have a familiar example of the lamellar structure in slate rocks and many minerals that occur in masses made up of separable laminae. The fibrous or columnar structure is common in seams of rocks, and sometimes in incrustations covering exposed surfaces; the material of the seam or crust is made up of minute fibers or prisms closely compacted together, produced by a rapid crystallization on the supporting surface. The granular structure is well seen in loaf sugar and statuary marble. 1. COLUMNAR STRUCTURE. The following are explanations of the terms used in describing the different kinds of columnar structure.. Fibrous; when the columns are minute and lie in the same direction; as gypsum and asbestus. Fibrous minerals very commonly have a silky luster: a fibrous variety of gypsum, and one of calc spar, have this luster very strongly, and each is often called satin spar. Reticulated; when the fibers, or columns, cross in various directions, and produce an appearance having some resemblance to a net. Stel1ated; when they radiate from a center in all direc. tions, and produce a star-like appearance. Ex. stilbite, gypsaum. What kinds of structure exist in massive minerals? Explain the different varieties of columnar structure, fibrous; reticulated, &c. IMPERFECT CRYSTALLIZATIONS. 53 Radiated, divergent; when the crystals radiate from a center, without producing stellar forms. Ex. quartz, gray antimony. 2. LAMELLAR STRUCTURE. In the lamellar structure, the laminue or leaves may be thick, or very thin; they sometimes separate easily, and sometimes with great difficulty. When the laminiae are thin and separate easily, the struc. ture is said to be foliaceous. Mica is a striking example, and the term micaceous is often used to describe this structure. When the laminae are thick, the term tabular is often ap. plied; quartz and heavy spar afford examples. The laminae may be elastic, as in mica, flexible, as in talc or graphite, or brittle, as in diallage. Small laminae are sometimes arranged in stellar shapes; this occurs in mica. 3. GRANULAR STRUCTURE. When the grains in the texture of a mineral are coarse, it is said to be coarsely granular, as in granular nrarble; when fine, finely granular, as in granular quartz; and if no grains can be detected with the eye, the structure is described as impalpable, as in chalcedony. Granular minerals, when easily crumbled by the fingers, are said to befriable. IMITATIVE SHAPES.-Massive minerals also take certain imitative shapes, not peculiar to either of these varieties of structure. The following terms are used in describing imitative forms: Globular; when the shape is spherical or nearly so: the structure may be columnar and radiating, or it may be concentric, consisting of coats like an onion. When they are attached, they are called implanted globules. Beniform; kidney-shaped. In structure, they are like globular shapes. Botryoidal; when a surface consists of a group of rounded prominences. The prominences or globules usually consist of fibers radiating from the center. Mammillary; resembling the botryoidal, but consisting of larger prominences. FiliJbrm; like a thread. Acicular; slender like a needle. Explain the varieties of lamellar structure; of granular structure; the several imitative shapes, globular; reniform, &c. 5* Lt)t 4STR UCTURE OF MINERALS. Stalactitic; having the form of a cylinder, or cone, hang. ing from the roofs of cavities or caves. The term stalactite is usually restricted to the cylinders of carbonate of lime hanging from the roofs of caverns: but other minerals are said to have a stalactitic form when resembling these in their general shape and origin. Chalcedony and brown iron ore are often stalactitic. Reticulated; net-like. Drusy; a surface is said to be drusy when covered with minute crystals. Amorphous; having no regular structure or form, either crystalline or imitative. The word is from the Greek, and means without shape. PSEUDOMORPHOUS CRYSTALS. A pseudomorphous* crystal is one that has a form which is foreign to the species to which the substance belongs. Crystals sometimes undergo a change of composition from aqueous or some other agency, without losing their form; for example, octahedrons of spinel change to steatite, still retaining the octahedral form. Cubes of pyrites are changed to red or brown iron ore. Again: crystals are sometimes removed entirely, and at the same time and with equal progress, another mineral is substituted; for example, when cubes of fluor spar are transformed to quartz. The petrifaction of wood is of the same kind. Again: cavities left empty by a decomposed crystal, are refilled by another species by infiltration, and the new mineral takes on the external form of the original mineral, as a fused metal the form of the mould into which it is cast. Again: crystals are sometimes incrusted over by other minerals, as cubes of fluor by quartz; and when the fluor is afterwards dissolved away, as sometimes happens, hollow cubes of quartz are left. The first kind of pseudomorphs, are pseudomorphs by alteration; the second, pseudonmorph.s by rep7lacement; the What is a pseudomorphous crystal? Wthat is the first, the second, the third and the fourth mode of pseudomorphism? What are they called? * From the Greek pseudes, false, and morphe, form. LUSTER OF MINERALS. 55 third, pseudomorphs by infiltrationz; the fourth, pseudomorphs by incrustation.* Pseudomorphous crystals are distinguished by having a different structure and cleavage from that of the mineral imitated in form, and a different hardness, and usually little luster. A large number of minerals have been met with as pseudomorphs. The causes of such changes have operated very widely and produced important geological results. CHAPTER IIl.-PHYSICAL PROPERTIES OF MINERALS. CHARACTERS DEPENDING ON LIGHT. The characters depending on light are of five kinds, and arise from the power of minerals to refect, transmit, or emit light. They are as follows: 1. Luster; 2. Color; 3. Diaphaneity; 4. Refraction; S. Phosphlorescence. LUSTER. 90. The luster of minerals depends on the nature of their surfaces, which causes more or less light to be reflected. There are different degrees of intensity of luster, and also different kinds of luster. a. The kinds of luster are six, and are named from some familiar object or class of objects. 1. Metallic: the usual luster of metals. Imperfect metallic luster is expressed by the term sub-metallic. 2. Vitreous: the luster of broken glass. An imperfect vitreous luster is termed sub-vitreous. Both the vitreous and sub-vitreous lusters are common. Quartz possesses the former in an eminent degree; calcareous spar often the lat. ter. This luster may be exhibited by minerals of any color. 3. Resinous: luster of the yellow resins. Ex. opal, zinc blende. 4. Pearly: like pearl. Ex. talc, native magnesia, stilbite, &c. When united with sub-metallic luster, the term metallic-pearly is applied. How are pseudomorphous crystals distinguished? What characters depend on light? Explain the varieties of luster, metallic, vitreous, &c. * This subject is farther treated of by the author in the Amer. Jour. of Science, vol. xlviii, pp. 66, 81, 397. 56 PHYSICAL PROPERTIES OF MINERAnLSo 5. Silky: like silk; it is the result of a fibrous structure. Ex. fibrous carbonate of lime, fibrous gypsum, and many fibrous minerals, more especially those which in other forms have a pearly luster. 6. Adamantine: the luster of the diamond. When submetallic, it is termed metallic-adamantine. Ex. some varieties of white lead ore. b. The degrees of intensity are denominated as follows: 1. Splendent: when the surface reflects light with great brilliancy, and gives well defined images. Ex. Elba iron ore, tin ore, some specimens of quartz and pyrites. 2. Shining: when an image is produced, but not a well defined image. Ex. calcareous spar, celestine. 3. Glistening: when there is a general reflection from the surface, but no image. Ex. talc, copper pyrites. 4. Glimmering: when the reflection is very imperfect, and apparently from points scattered over the surface. Ex. flint, chalcedony. A mineral is said to be dull when there is a total absence of luster. Ex. chalk. COLOR, In distinguishing minerals, both the external color and the color of a surface that has been rubbed or scratched, are observed. The latter is called the streak, and the powder abraded, the streak-powder. The colors are either metallic or non.metallic. The metallic are named after some familiar metal, as copper-red, bronze-yellow, brass-yellow, gold-yellow, steel. gray, lead-gray, iron-gray. The non-metallic colors used in characterizing minerals, are various shades of white, gray, black, blue, green, yellow, red and brown. There are thus snow-white, reddish-white, greenish-white, milkl-white, yellowish-white; Bluish-gray, smoke-gray, greenish-gray, pearl-gray, ash. gray; Velvet-black, greenish-black, bluish-black; Azure-blue, violet-blue, sky-blue, Indigo-blue; Emerald-green, olive-green, oil-green, grass-green, applegreen, blackish-green, pistachio-green (yellowish); What is observed respecting color? COLOR OF MINERALS. 57 Sulphur-yellow, straw-yellow, wax-yellow, ochre-yellow, honey-yellow, orange-yellow; Scarlet-red, blood-red, flesh-red, brick-red, hyacinth-red, rose-red, cherry-red; Hair-brown, reddish-brown, chesnut-brown, yellowish. brown, pinchbeck-brown, wood-brown. A play qf colors: this expression is used when several prismatic colors appear in rapid succession on turning the mineral. The diamond is a striking example; also precious opal. Chavge of colors: when the colors change slowly on turning in different positions, as in labradorite. Opalescence when there is a milky or pearly reflection from the interior of a specimen, as in some opals, and in cat's eye. Tridescence: when prismatic colors are seen within a crystal; it is the effect of fracture, and is common in quartz. Tarnish: when the surface colors differ from the interior; it is the result of exposure. The tarnish is described as irised, when it has the hues of the rainbow. Polychroism:* the property, belonging to some prismatic crystals, of presenting a different color in different directions The term dichroismt has been generally used, and implies different colors in two directions, as in the mineral iolite, which has been named dichroite because of the different colors presented by the bases and sides of the prism. Mica is another example of the same. The more general term has been introduced, because a different shade of color has been observed in more than two directions. These different colors are observed only in crystals with unequal axes. The colors are the same in the direction of equal axes, and often unlike in the direction of unequal axes. This is the general principle at the basis of polychroism. What is a play of colors? change of colors? opalescence? iridescence? tarnish? dichroism and polychroism? Mention examples of this last property; also the law relating to it. e From the Greek polus, many, and chroa, color. tFrom the Greek dis, twice, and chroa. 58 PHYSICAL PROPERTIES OF 3IINERALS. DIAPHANEITY. Diaphaneity is the property which many objects possess of transmitting light; or in other words, of permitting more or less light to pass through them. This property is often called transparency, but transparency is properly one of the degrees of diaphaneity. The following terms are used to express the difebrent degrees of this property: Transparent: a mineral is said to be transparent when the outlines of objects, viewed through it, are distinct. Ex. glass, crystals of quartz. Subtransparent, or semitransparent: when objects are seen but their outlines are indistinct. Translucent: when light is transmitted, but objects are not seen. Loaf sugar is a good example; also Carrara marble. Subtranslucent: when merely the edges transmit light faintly. When no light is transmitted, the mineral is de. scribed as opaque. REFRACTION AND POLARIZATION. Light is always bent out of its course on passing from one medium into another of different density: as from air into water, or fiom water into air. This bending of the rays of light is called refraction. Thus if a ray of light, as R S, 92 pass into water at S, it becomes changed in direction to S U, instead of going M \ straight in its course, R S T. The line s.a S c is a perpendicular to the surface of ~~__ -_ _ gthe water, and the greater refraction of A=___~~ — |the water is seen by the bending of the ray toward this perpendicular. If a circle be described about S as a center, and the lines R a and U b be drawn perpendicular to a c, or parallel to the surface of the water, we see by these lines the exact relation between the amount of refraction in these two cases; for the refraction in water is as much greater than in air as U b is less than R a.* This relation is called the What is diaphaneity? Explain the terms transparent, &c. What is meant by refraction? Explain from the figure. e In mathematical language, U b is the sine of the angle of refraction, and a R the sine of the angle a S R, the angle of incidence; the ratio between the two sines is constant, it being alike for every angle of incidence. AtEFRACTION AND POLARIZATION DF LIGHT. 59 index of refraction. It is about 1~ for water, or more accurately, 1'335. With diamond, the ray would be bent in the direct S V, which indicates a much greater amount of re. fraction; its index is nearly 2~, or correctly, 2.439. The eye at R, looking into a diamond in the direction R S, would see an object in the direction of S V, and not in that of S T. The index of refraction has been obtained for many substances, of which the following are a few: Air, 1.000 Cale spar, 1'654 Tabasheer, 1'211 Spinel, 1'764 Ice, 1'308 Sapphire, 1P794 Cryolite, 1'349 Garnet, 1P815 Water, 1P335 Zircon, 1-961 Fluor spar, 1P434 Blende, 2'260 Rock salt, 1'557 Diamond, 2'439 Quartz, 1P548 Chromate of lead, 2'974 DOUBLE REFRACTION.-Many crystals possess the property of,refracting light in two directions, instead of one, and objects seen through them consequently appear double. This is called double refraction. It is most conveniently exhibited with a crystal of calc spar, and was first noticed in a pellucid variety of this mineral from Iceland, called from,the locality Iceland spar. On drawing a line on paper and placing the crystal over it, two lines are seen instead of oneone by ordinary refraction, the other by an extraordinary refraction. If the crystal,'as it lies over the line, be turned around, when it is in one position the two lines will come together. Instead of a line, make a dot on the paper, and place the crystal over the dot: the two dots seen will not come together on revolving the crystal, but will seem to revolve one around the other. The dot will, in fact, appear double through the crystal in every direction except t~hat of the vertical axis, and this direction is called the axis of double refraction. To view it in this direction, the ends must be ground and polished. The divergence increases on passing from a view in the direction of the axis to one at right angles with it, where it is greatest. In some substances, the refraction of the extraordinary ray is greater in the latter direction than that of the ordinary- ray, and in others it is less. What is double refraction? What takes place on revolving a transparent rhomb of calc spar over a line or dot? In what direction is there no double refraction, and in which is it greatest? 60 PHYSICAL PROPERTIES OF MINERALS. In calc spar it is less, it. diminishing from 1-654 to 1-483. In quartz it is greater, it increasing from 1-5484 to 1'5582. The former is said to have a negative axis, the latter a positive. This property of double refraction belongs to such of the fundamental forms as have unequal axes; that is, to all except those of the monometric system. Those forms in which the lateral axes are equal, (the dimetric and hexagonal systems,) have one axis of double refraction; and those in which they are unequal, (the trimetric, monoclinate and triclinate systems,) have two axes of double refraction.* Both rays in the latter are rays of extraordinary refraction. In niter, the two axes are inclined about 5~ to each other; in arraogonite, 180 18; in topaz, 65~. The positions of the axes thus vary widely in different minerals. POLARIZATION. —The extraordinary ray exhibits a pecu. liar property of light, termed polarization. Viewed by means of another- doubly-refracting crystal, or crystalline plate, (called from this use of it an analyzing plate,) the ray of light becomes alternately visible and invisible as the latter plate is revolved. If the polarized light be made to pass througb a crystal possessed of double refraction, and then be viewed in the manner stated, rings of prismatic colors are developed, 93 94 95 96 and on revolving the analyzing plate, the colored rings and What is meant by positive and negative double refraction? What crystalline forms exhibit double refraction? which have one and which two axes of double refraction? Whai are the effects due to polarization' The figures in the note to page 42, represent the form of the molecules corresponding to these three conditions: 1, a sphere; 2, an ellipsoid with equal transverse axes; 3, an ellipsoid with unequal lateral axes. PIOSPIIORESCENCE 61 intervening dark rings successively change places. If crys. talline plates, having one axis of double refraction, be viewed in the direction of the axis, the rings are circles, and they are crossed by a dark or light cross. Figure 93 shows the position of the colored rings and cross in calc spar, and figure 94, the same at intervals of 90' in the revolution of the plate. With a crystal having two axes of double refrac. tion, there are two series of elliptical rings, as in figures 95, 96; these figures show the character of the rings in niter, the latter alternating with the former in the revolution of the plate. The same results are produced when the light is polarized by other means. For example, if a ray of light be reflected fiom a plate of glass at a certain angle, (56' 45',) it is polarized; and on causing this ray to pass through crystals, as above, similar rings are shown with the same succession of changes on revolving the analyzing plate. There are some monometric: 97 crystals which have the property of polarization. The accompanying figure of a crystal ofanalcime, /' by Sir David Brewster, exhibits a, singular symmetrical arrangement of lines of prismatic colors and;; darlk alternating lines with cross bands, producing a very brilliant effect. An irregular polarization has also been detected in some diamonds. rPOSPHORESCENCE. Several minerals give out light either by friction or when gently heated. This property of emitting light is called phosphorescence. Two pieces of white sugar struck against one anoth er give a feeble light, which may be seen in a dark place The same effect is obtained on striking together fragments of quartz, and even the passing of a feather rapidly over some specimens of zinc blende, is sufficient to elicit light. Fluor spar is the most convenient mineral for showing phosphorescence by heat. On powdering it, and throwing What is said of the appearance of certain crystals in polarized light? What is phosphorescence? Mention examples explainir g the different modes of exhibiting it. 6 62 PHYSICAL PROPERTIES OF MINERALS. it on a shovel heated nearly to redness, the whole takes ola a bright glow. In some varieties, the light is emerald green; in others, purple, rose, or orange. A massive fluor, fiom Huntington, Connecticut, shows beautifully the emerald green phosphorescence. Some kinds of white marble, treated in the same way, give out a bright yellow light. After being heated for a while, the mineral loses its phosphorescence; but a few electric shocks will, in many cases, to some degree, restore it again. ELECTRICITY AND MAGNETISM. ELECTRICITY.-Many minerals become electrified on being rubbed, so that they will attract cotton and other light substances; and when electrified, some exhibit positive, and others negative electricity, when brought near a delicately suspended magnetic needle. The diamond, whether polished or not, always exhibits positive electricity, while other gems become negatively electric in the rough state, and positive only in the polished state. Friction with a feather is sufficient to excite electricity in some varieties of blende. Some minerals, thus electrified, retain the power of electric attraction for many hours, as topaz, while others lose it in a few minutes. Many minerals become electric when heated, and such species are said to be pyro-electric, from the Greek pur, fire, and electric. If a prism of tourmaline, after being heated, be placed on a delicate frame, which turns on a pivot like a magnetic needle, on bringing a magnet near it, one extremity will be attracted, the other repelled, thus indicating the polarity alluded to. The same is better shown if the ends of the crystal be brought near the poles of a delicately suspended magnetic needle. The prisms of tourmaline have different secondary planes at the two extremities, or, as it is expressed, are hemio hedrally modified (page 37.) Several other minerals have this peculiar electric property. especially boracite and topaz, which, like tourmaline, are hemihedral in their modifications. Boracite crystallizes in Will electricity restore the phosphorescent property when it is lost by heating a mineral? What two modes are there of exciting electricity in minerals? What is said of the diamond as compared with other gems? What is a pyro-clectric? What is said of tourmaline? what of topaz and borecite? SPECIFIC GRAVITY. 63 cubes, with only the alternate solid angles similarly replaced (figs. 40, 41, page 37.) Each solid angle, on heating the crystals, becomes an electric pole; the angles diagonally opposite, are differently modified and have opposite polarity. AMAGNETIs.q.-Lodestone includes certain specimens of an ore of iron, called magnetic oxyd of iron, having the power of attraction like a magnet; it is common in many ore beds where this ore of iron occurs. When mounted like a horseshoe magnet, a good lodestone will lift a weight of many pounds. This is the only mineral that has decided magnetic attraction. But several ores containing iron are attracted by the magnet, or, when brought near a magnetic needle, will cause it to vibrate; and moreover, the metals nickel, cobalt, manganese, palladium, platinum and osmium, have been found to be slightly magnetic. Many minerals become attractable by the magnet after being heated, that are not so before heating. This arises from a partial reduction, developing the protoxyd of iron. SPECIFIC GRAVITY. The specific gravity of a mineral is its weight compared with that of some substance, taken as a standard. For solids and liquids, distilled water at 60~ F. is the standard ordinarily used; and if a mineral weighs twice as much as water, its specific gravity is 2; if three times, it is 3. It is then necessary to compare the weight of the mineral with the weight of an equal bulk of water. The process is as follows: First weigh a fragment of the mineral in the ordinary way, with a delicate pair of scales: next sus- 98 pend the mineral by a hair or fiber of silk to one of the scales, immerse it thus suspended in a tumbler of water, (keeping the scales clear of the water,) and weigh it again: subtract the second weight from the first, to ascertain the loss by immersion, and divide the first by the dif- ference obtained: the result is the specific gravity. The loss by immersion is What ore is at times possessed of magnetic attraction? What is said of other minerals as regards magnetism? What is specific gravity? Explain. Mention the mnode of ascetaiining specific gravity. 64 PHYSICAL PROPERTIES OF MINERALS. equal to the weight of the same bulk of water as the mineral.* A better and more simple process than the above, and one available for porous as well as compact minerals, is performed with a light glass bottle, capable of holding exactly a thousand grains (or any known weight) of distilled water. The specimen should be reduced to a coarse porwder. Pour out a few drops of water from the bottle, and weigh it; then add the powdered mineral till the water is again to the brim, and reweigh it: the difference in the two weights, divided by the loss of water poured out, is the specific gravity sought. The weight of the glass bottle itself is here supposed to be balanced by an equivalent weight in the other scale. HARDNESS. The comparative hardness of minerals is easily ascertained, and should be the first character'attended to by the student in examining a specimen. It is only necessary to draw the file across the specimen, or to make trials of scratching one with another. As standards of comparison, the following minerals have been selected, increasing gradually in hardness firom talc, which is very soft and easily cut with a knife, to the diamond, which nothing will cut. This table is called the scale of hardness. i, talc, common foliated variety; 2, rock salt; 3, calc spar, transparent variety; 4, fluor spar, crystallized variety; 5, apatite, transparent crystal; 6, feldspar, cleavable variety; 7, quartz, transparent variety; 8, topaz, transparent crystal;: 9, sapphire, cleavable variety; 10, diamond. If on drawing a file across a mineral, it is impressed as easily asfluor spar, the hardness is said to be 4; if as easily asfeldsparthe hardness is said to be 6; if more easily than What other mode is fitted for porous as well as compact minerals? How is the hardness of minerals ascertained? What is the scale of hardness? Explain its use. What directions are given for trials of hardness? e For perfectly accurate results, the most delicate scales and weights should be used, and great care be observed in the trial. The purity and temperature of the water should also be attended to, and the height of the barometer. For the latter, an allowance is made for any variation from a height of 30 inches. The temperature of water at its maximum density, or at 390 1 F., is recommended as preferable to 600 F. FRACTURE. 65 feldspar, but with more difficulty than apatite, its hardness is described as 5~ or 5'5. The file should be run across the mineral three or four kimes, and care should be taken to make the trial on angles equally blunt, and on parts of the specimen not altered bl exposure. Trials should also be made by scratching the specimen under examination with the minerals in the above scale, as sometimes, owing to a loose aggregation of particles, the file wears down the specimen rapidly, although the particles are very hard. STATE OF AGGREGATION. Solid minerals may be either brittle, sectile, malleable, flexible or elastic. Fluids are either gaseous or liquid. 1. Brittle: when parts of the mineral separate in powder on attempting to cut it. 2. Sectile: when thin pieces may be cut off with a knife but the mineral pulverises under a hammer. 3. Malleable: when slices may be cut off, and these slices will flatten out under the hammer. Example, native gold and silver., Flexible: when the mineral will bend, and remain bent after the bending force is removed. Example, talc. 5. Elastic: when after being bent, it will spring back to its original position. Example, mica. A liquid is said to be viscous, when on pouring it the drops lengthen and appear ropy. Example, petroleum. FRACTURE. The following are the several kinds of fracture in minerals: 1. Conchoidal: when the mineral breaks with a curved, or concave and convex surface of fracture. The word con. choidal is from the Latin concha, a shell. Flint is a good example. 2. Even: when the surface of fracture is nearly or quite flat. 3. Uneven: when the surface of fracture is rough with numerous small elevations and depressions. 4. Hackly: when the elevations are sharp or jagged, as in broken iron. Explain the use of the term brittle; sectile; malleable, &c. Explain the use of the term conchoidal; even; uneven. 6* 66 CHEMICAL PROPERTIES OF MINERALS. TASTE. Taste belongs only to the soluble minerals; the kinds are1. Astringent: the taste of vitriol. 2. Sweetish-astringent: the taste of alum. 3. Saline: taste of common salt. 4. Alkaline: taste of soda. 5. Cooling: taste of saltpeter. 6. Bitter: taste of epsom salts. 7. Sour: taste of sulphuric acid. ODOR. Excepting a few gases and soluble minerals, minerals in the dry, unchanged state, do not give off odor. By friction, moistening with the breath, the action of acids and the blow. pipe, odors are sometimes obtained, which are thus designated: 1. Alliaceous: the odor of garlic. It is the odor of burning arsenic, and is obtained by friction and more distinctly by means of the blowpipe from several arsenical ores. 2. Horse.radish odor: the odor of decaying horse-radish. It is the odor of burning selenium, and is strongly perceived when ores of this metal are heated before the blowpipe. 3. Sulphureous: odor of burning sulphur. Friction will elicit this odor from pyrites, and heat from many sulphurets. 4. Fetid: the odor of rotten eggs or sulphuretted hydrogen. It is elicited by friction from some varieties of quartz and limestone. 5. Argillaceous: the odor of moistened clay. It is given off by serpentine and some allied minerals when breathed upon. Others, as pyrargillite, afford it when heated. CHAPTER IV.-CHEMICAL PROPERTIES OF MINERALS. ACTION OF ACIDS. Acids are used in distinguishing certain minerals that are decomposed by them. The acids employed are either the sulphuric, muriatic, or nitric. Carbonate of lime, (calcaWhat taste is.astringent? sweetish astringent? saline? What will develop odor in some minerals? What is understood by an alliaceous odor? What mineral when heated produces this odor? What is the odor of fumes of selenium? How is a sulphureous odor obtained from certain minerals? What gas has a fetid odor? What is an argillaceous odor? USE OF THR BLOWPIPE. 67 reous spar,) when dropped into either of these acids gives off bubbles of gas, which effect is called effervescence. The same result takes place with some other minerals. The acid used in these tests, should be half water; and to avoid error, it is best to put a little of it in a test tube, and drop in small fragments of the coarsely powdered mineral. Some. times heat will cause an effervescence, which does not take place with cold acid. Often effervescence arises from some impurity present, which is discontinued before the solution of the mineral in the acid is complete. Other minerals, that do not effervesce in the acids, become changed to a jelly-like mass. For trials of this kind, the strong acids should generally be used. The powdered mineral is allowed to remain for a while in the acid, and gradually a jelly-like mass is formed. Often heat is required, and in that case, the jelly appears, as the solution cools. The minerals belonging to the zeolite family more especially undergo this change from the action of acids, and it arises from the separation of their silica in a gelatinous state. BLOWPIPE. To ascertain the effect of heat on minerals, A small instrument is used called *a blow- 100 101 102 pipe. In its simplest form, 1i (fig. 100,) it is merely a bent tube of small size, 8 to 10 inches long, terminating at one end in a minute orifice, not larger than a pin hole. It is used to concentrate the o flame of a candle or lamp on a mineral, and this is done by blowing through it while the smaller end is just within the flame. Figures 101 and 102 are other forms of the blowpipe, containing air chambers (o) to receive the moisture which is condensed in the tube! L What is effervescence, and how produced? How should the acid be used? How are some minerals made to gelatinize? On what does ihis property depend? What is the object of a blowpipe? 68~ CHEMIICAL PROPERTIES OF MINERALSo during the blowing; the moisture, unless thus removed, is often blown through the small aperture and interferes with the experiment. The air chamber in figure 102 is a cylindel, into which the tube a b c is screwed at c, and the smaller piece d e f, at d. For the convenience of packing it away, there is a screw at b. The part b c, after unscrewing it, may be run into the part a b, through the large end, (a,) and screwed up again, and thus it is half the length it has when arranged for use. The mouth piece e f screws off, and is made of platinum in order that it may be cleaned when necessary by immersion in an acid. The best material for the blowpipe is silver, or if a cheaper material is desired, tinned iron with the piece ef of brass. Brass gives a disagreeable smell to the moist fingers. In using the blowpipe, it is necessary to breathe and blow at the same time, that the operator may not iuterrupt the flame in order to take breath. Though seemingly absurd, the necessary tact may easily be acquired. Let the student first breathe a few times through his nostrils, while his cheeks are inflated and his mouth closed. After this practice, let him put the blowpipe to his mouth, and he will find no difficulty in breathing as before; while the muscles of the inflated cheeks are throwing the air they contain through the blowpipe. When the air is nearly exhausted, the mouth may again be filled through the nose without interrupting the process of blowing. A lamp with a large wick, so as to give a broad flame, and fed with olive oil, is best; but a candle is more conve. niently carried about when travelling. The wick should be bent in the direction the flame is to-be blown. The flame has the form of a cone, yellow without and blue within. The heat is most intense just beyond the extremity of the blue flame. In some trials, it is necessary that the air should not be excluded from the mineral during the experiment, and when this is the case, the outer flame is used. The outer is called the oxydating* flame, and the inner the reducing flame. Explain the structure and mode of use. What is said of the flame of a candle before the blowpipe? Which is the oxydating, and whichthe reducing flame? * It is so called because when thus heated, oxygen, one of the constituents of the atmosphere, comlbines in many cases with some parts of the assay (or substance under experiment.) USE OF THE BLOWPIPE. 69 The mineral is supported in the flame, either on charcoal, or by means of steel forceps, (fig. 103,) with platinum extremities (a b); the forceps are opened by pressing 103 on the pins p p. The charcoal should be firm b and well burnt. Charcoal is especially necessary when the reduction of the assay needs the presence of carbon; and platinum when simple heat is required. Platinum foil for enveloping the mineral, and small platinum cups are also used. When nothing better is at hand, the mineral mica or kyanite may be employed. The fragment of mineral under trial should be less than half a pea in size, p and often a thin splinter is required.' To test the presence of water or a volatile ingre. dient, the mineral is heated in a glass tube or test vial. The tube may be three or four inches long and as large as a quill. The flame is directed against the exterior of the tube beneath the assay, and —the volatilized substance usually condenses in the upper part of the tube. By inserting into the upper end of the tube a strip of litmus or other test paper, it is ascertained whether the* fumes are acid or not. Some species require for fusion the aid of what are calledfluxes. Those more commonly used are borax, salt of phosphorus, and carbonate of soda. They are fused to a clear globule, to which the mineral is added;. or powdered and made up into a ball with the moistened mineral in powder. In this way some minerals are fused that cannot be attacked otherwise, and nearly all species, as they melt, undergo certain changes in color, arising from changes in composition, which are mentioned in describing minerals. The above mentioned fluxes also are often required in order to obtain the metals from the metallic ores. On heat. ing a fragment-of copper pyrites with borax, a globule of copper is obtained; and tin ore heated with soda yields a globule of tin. What instruments or appliances are used for holding minerals before the blowpipe? How is the presence of water ascertained? How may its acidity be tested? How are the common fluxes employed, and what is their use? 70 CHEMICAL PROPERTIES OF MINIERALS. The following table contains the reactions of some of the metallic oxyds with the ordinary fluxes:* Borax. Salt of Phosphorus. Soda. Titanic acid 0, colorless or 0, colorless, trp Deep yw, hot; milky w or gyh, cold Oxyd of iron 0, red,hot; ywh 0, red, hot; paler or or colorless, colorless, cold cold R, green or bh gn Oxyd of cerium 0, r; yw on 0, fine r, hot; colcooling; w orless, cold enamel on flaming R, colorless or w enamel Oxyd of manga- 0, amethystine 0. amethystine P1. trp gn, hot; nese bh-gn, cold Oxyd of cobalt 0, trp blue O, blue Pl. pale r, hot; gray, cold Oxyd of chrome O, bn, hot; pale 0, green 0. Pl. dull orgn, cold ange; op & yw R, emerald-gn, R, green on cooling cold Oxyd of copper O, green O, green P1. gol, hot; col, R, colorless, R, colorless, hot; r op, cold hot; but sud- on solidifying denly opaque and rdh on cooling The following are other reactions: Nitrate of cobalt in solution added to the assay after heat. ing to redness, and then again heated, produces before fusion a blue color for alumina and a pale-red for magnesia. Boracic acid fused with a phosphate produces a globule, into which if the extremity of a small iron wire be inserted, and the whole heated in the reduction flame, the globule attached to the wire will be brittle, as proved by striking it with a hammer on an anvil. Before this trial it should be ascertained that no sulphuric or arsenic acid is present, which also may form a brittle globule with the iron; nor any metallic oxyd reducible by the iron. For what is nitrate of cobalt used? How and for what is boracic acid used? O0 stands for oxydating flame; R for reducing flame; Ch for charcoal; trp for transparent; bh bluish; ywv yellow; gn green; r red; gyh grayish; w white; PI in platinum forceps; op opaque. CLASSIFICATION OF MINERALS. 71 Tin-foil is used to fuse with certain peroxyds of metals to reduce them to protoxyds. The assay, previously heated in the reducing flame, should be touched with the end of the tin foil; a very minute quantity of a metallic oxyd is thus detected. Saltpeter added along with a flux to a compound containing manganese, gives the amethystine color, when the quan. tity is too small to be detected without it. Potash salts, if there is no soda present, give a slightly violet tinge to the flame. Soda salts give the flame a deep yellow color. Lithia salts give the flame a reddish tinge; the silicates require the addition of some fluor spar and bisulphate of potash. By adding soda and heating on platinum, the lithia stains the platinum brown. Sulphurets, Su7phates. A glass made of soda and silica becomes red or orange yellow when sulphur is present. Heated on charcoal with soda, and then adding a drop of water, they yield sulphuretted hydrogen, which blackens a test paper containing acetate of lead. Sulphurets heated in a glass tube closed below, with litmus paper above, redden the litmus paper, and yield usually a sulphureous odor. Seleniets give off a horse-radish odor. Arseniurets give off an odor like garlic, which is brought out by heating with soda in the reduction flame, if not other. wise perceptible; heated in a tube, orpiment is condensed, Fluorids. Heated with salt of phosphorus, previously melted in a glass tube, the glass is corroded; and Brazil paper placed in the tube becomes yellow. The salt of phosphorus for this trial should be free from all chlorids.'Nitrates detonate on burning coals. CHAP. V.-CLASSIFICATION OF MINERALS. Under the term mineral, as explained, are included all inorganic substances occurring in nature. These substances have been found to'consist of various elements, some few How and for what is tin-foil used? saltpeter?-What is said of the constitution of minerals? * For full information on the use of the blowpipe and its reactions there is no better work than Berzelius on " the Use of the Blowpipe," translated by J. O. Whitney. 238 pp. 8vo. Boston, 1845. 72 CLASSIFICATION- OF -MINERALS. species being each a simple element alone, and others consisting of two or more elements in a state of combination. The various native metals, as native gold, silver, copper, mercury, are some of the elements. Iron ores are compounds of the element iron with some other element or elements, as oxygen, sulphur,; or oxygen and carbon, &c. Marble is a compound of three elements, calcium, oxygen and carbon. Water consists of two elements, hydrogen and oxygen. Diamond is the simple element carbon, which is identical with pure charcoal. All the so-called elements of matter are found in the mineral kingdom, either in a pure or combined state; and it is the object of chemical analysis to ascertain the proportions of each in the constitution of the several minerals. Upon these results depends to a great degree our knowledge of those relations of the species upon which the classification of minerals is based. The number of elemental substances in nature, according to the most recent results of chemistry, is fifty-nine. Of these, forty-three are metals, and five are gases; the remainder, as, for instance, sulphur and carbon, are solids without a metallic luster, excepting one (bromine) which is a liquid at the ordinary temperature. Of these fifty-nine elements, very much the larger part are of rare occurrence in nature. The rocks of the globe, with their most common minerals, are made up of about thirteen of the elements. These are the gases oxygen, hydrogen, nitrogen, chlorine; the non-metallic elements carbon, sulphur, silicon; the metals calcium, (basis of lime,) sodium, (basis of soda,) potasszum, (basis of potash,) magnesium, (basis of magnesia,) aluminium. (basis of alumina, the principle constituent of clay,) -with iron. The element silicon combined with oxygen, forms silica. In this state, it is the mineral quartz, the most common in the constitution of the rocks of the globe: it is a constituent of granite, mica slate and the allied rocks, of the hard granular quartz rock; and it is the essential part of all sandstones and millstone grits, as well as the principal ingredient of the sands of the sea shore and of most soils. Combined with lime, potash or. soda, magnesia or alumina, and often with iron, it forms nearly all the other mineral inWhat is the number of elements, and how many are metals? How many constituents are essential to the rocks of the globe, and what are they? What is said of quartz? CLASSIFICATION OF MINEfRALS. 73 gredients of granite, mica slates, volcanic rocks, shales, sandstones and various soils. No element is therefore more important than this in the constitution of the earth's strata: and it is specially fitted for this preeminence by its superior nardhess, a character it communicates to the rocks in which it prevails. Next to silica, rank lime and carbon; for carbon with oxygen constitutes carbonic acid, and this combined with lime, produces carbonate of lime, the ingredient which, when occurring in extended beds, we call limestone and marble. Again, lime combined with sulphur and oxygen, (sulphuric acid,) makes sulphate of lime, or common gypsum. Iron is very generally diffused; it is one of the constituents of many siliceous minerals, and forms vast beds of ore. Oxygen, as has been implied, is a constituent in all'the rocks above mentioned, and besides, is an essential part of the atmosphere and water; it is the most universally diffused of the elements. It is united with hydrogen in the constitution of water, and with nitrogen in the constitution of the atmosphere. Chlorine combined with sodium constitutes common salt, which occurs in sea water and brine springs, and is also found in vast beds in some rock strata. It is thus seen how few are the elements essential to the framework of our globe. The various metallic ores, of less general diffusion, are however of vast economical importance to man, and multiply considerably the number of mineral species. Those important to the general student, however, are comparatively few. The whole number of well established species in the mineral kingdom is about 500; of these, more than two-thirds are known only. to the mineralogist. It is the province of chemistry to discuss fully the nature of the elements, and their modes of combination. It is sufficient to add here, for the benefit of any who may not have the requisite elementary chemical knowledge, how the chem. ical names of minerals indicate their composition. Terms such- as oxyd of iron, chlorid of iron, express a combination of iron with the element oxygen, or chlorine; so also sulphuret of iron is a compound of iron with sulphur. The force of the terminations id or uret is always as here explained. Protoxyd and peroxyd imply different proportions Which are the next most common ingredients of rocks? Mention the other ingredients alluded to. What is an oxyd? a chlorid? a sulphuret? a carbonate? l7 74 CLASSIFICATION OF MINERALS. of oxygen, the latter the highest. Terms such as carbonate of lime, sulphate of lime, indicate that the substance is come posed of an acid-carbonic acid, or sulphuric acid in the instances cited, with lime. So silicate of soda is a compound of soda and silicic acid (or silica); and all such compounds are theoretically said to consist of an acid and a baselime and soda, in the cases mentioned, being bases. The true foundation of a species in mineralogy must be derived from crystallization, as the crystallizing force is fundamental in its nature and origin; and it is now generally admitted that identity oJ crystallineform and structure is evidence of identity of species. This principle unites certain distinct chemical compounds into the same species: —for example, a silicate of magnesid and a silicate of iron crystallizing alike, constitute but one species in mineralogy, though chemically so different. Oxyd of iron and magnesia are themselves nearly identical in molecularform and size, and on this fact depends their power of replacing one another even in complex compounds. They are therefore said to be isomorphous (from the Greek isos, similar, and morphe, form.) There are many groups of these isomorphous substances, and some knowledge of them is necessary to enable the reader to understand why different varieties of a mineral species may differ so widely, as they often do, in composition. Some of these groups are as follows: 1. Alumina, peroxyd of iron, peroxyd of manganese. 2. Lime, magnesia, protoxyds of iron, manganese and zinc. 3. Baryta, strontia, oxyd of lead. 4. Sulphur, selenium, tellurium. 5. Tungsten, molydenum. 6. Phosphoric acid, arsenic acid. In epidots the alumina may be replaced by peroxyd of iron or manganese, and the magnesia in part or wholly by lime, or the protoxyds of iron or manganese. The same is true of garnet and several other minerals. The rhombohedrons of carbonate of lime, carbonate of iron, and carbonate of magnesia, are very nearly identical in angle, because the bases are ismorphous. This subject is illustrated by the greater part of mineral species. What is a sulphate? a silicate? What is the test of identity of species in mineralogy? What are isomorphous substances? What are the common groups of isomorphous substances in minerals? Explain by examples. CLASSIFICATION OF MINERALS. 75 GENERAL VIEW OF THE CLASSIFICATION OF MINERALS. The classification adopted in this work is based on the constitution of minerals. The following is a general view of it: CLASS I. Gases: consisting of or containing nitrogen or hydrogen. CLASS II. Water. CLASS III. Carbon, and compounds of carbon. CLASS IV. Sulphur. CLASS V. Haloid minerals: compounds of the alkalies and earths, with the soluble acids (sulphuric, nitric, carbonic, &c. or water,) or of their metals with chlorine or fluorine. 1, Salts of ammonia,; 2, of potash; 3, of soda; 4, of baryta; 5, of strontia; 6, of lime; 7, of magnesia; 8, of alumina. CLASS VI. Earthy minerals: silica and siliceous or aluminous compounds of the alkalies and earths-i, silica; 2, lime; 3, magnesia; 4, alumina; 5, glucina; 6, zirconia; 7, thoria. CLASS VII. Metals and metallic ores, (exclusive of the metals of the alkalies and earths): 1, Metals easily oxydiz. able-cerium, yttrium, uranium, iron, manganese, chromium, nickel, cobalt, zinc, cadmium, bismuth, lead, mercury, copper, titanium, tin, molybdenum, tungsten, tellurium, antimony, arsenic; 2, Noble metals: platinum, iridium, palladium, gold, silver. tExplain the classification adopted. 76 GASEOUS MINERALS. CLASS I.-GASES. )"The gases occurring native are as follows: 1. contaimzng or consisting of nitrogen: atmospheric air, nitrogen. 2. containing hydrogen: carbureted hydrogen, phosphureted hydrogen, sulphureted hydrogen, muriatic acid. 3. containing carbon or sulphur: carbonic acid, sulphurous acid. ATMOSPHERIC AIR. 1. Atmospheric air is the air we breathe. It consists of oxygen 21 per cent. by weight, and nitrogen 79 per cent., with a small proportion of carbonic acid. It has neither color, odor, nor taste. It supports life and combustion through the oxygen which it contains, this gas being used or absorbed in respiration as well as in the burning of wood or a candle. The oxygen thus consumed is restored to the air again by vegetation which gives out oxygen through the day, and in this way the quality of the atmosphere requisite for life is sustained. It is about 815 times lighter than water, and 11,065 times lighter than mercury. A hundred cubic inches weigh about 31 grains. NITROGEN GAS. Nitrogen destroys life, and has neither color, odor nor taste. It is one of the constituents of the atmosphere. It bubbles up through the waters of many springs, having been derived from air by some decompositions in progress within the earth, by which the oxygen of the air is absorbed. Lebanon springs in Columbia county, New York, and a region in the town of Hoosic, Rensselaer county, afford large quantities of this gas. There is another locality at Canoga, Seneca county, where the water is in violent ebullition from the escape of the gas; its temperature is 40~ F. There are other nitrogen springs in Virginia, west of the Blue Ridge at Warm and Hot Springs; in Buncombe county, N. C.; and on the Washita in Arkansas. At Bath, in England, nitrogen is escaping from the tepid springs at the What gases occur in nature? What is the constitution of the atmosphere? its general characters? the weight? What is said of the characters of nitrogen? Where does nitrogen occur in nature? GASES CONTAINING HYDROGEN. 77 rate of 267 cubic inches a minute, or 222 cubic feet a day. The gas from these nitrogen springs contains only 2 or 3 per cent. of oxygen, and often a very little carbonic acid. CARBURETED HYDROGEN. Carbureted hydrogen consists of carbon 75, hydrogen 25; burns with a bright yellow flame. It is the same gas nearly that is used for lighting the streets in some of our cities. It issues abundantly from some coal beds and beds of bitumi. nous slate. At Fredonia, in western New York, near Lake Erie, it is given out so freely from a slate rock, that it is used for lighting the village. A vessel containing 220 cubic feet is' filled in about 15 hours. A light-house at Portland harbor, on Lake Erie, four miles from Fredonia, is also lighted with the same gas from other springs. Another carbureted hydrogen, burning with a pale blue flame, rises in bubbles through pools of water, owing to vegetable decomposition in the soil beneath. PHOSPHURETED HYDROGEN. Phosphureted hydrogen consists of phosphorus 91'29, ant hydrogen 8'71. It takes fire spontaneously. The phos. phoric matter, called Jack-o'-lantern, sometimes seen float. ing over marshy places, is supposed to be phosphureted hydrogen. SULPHURETED HYDROGEN. Sulphureted hydrogen consists of sulphur 94'2, hydrogen 5'8. It has the odor and taste of putrescent eggs and burns with a bluish flame. It is abundant about sulphur springs, issuing freely from the waters, as in western New York and in Virginia. It is sometimes found about volcanoes. It blackens silver and also a common cosmetic made of oxyd of bismuth. MURIATIC AcID.-IHydrochloric Acid. Muriatic acid gas consists of hydrogen 2'74, chlorine 97'26. It has a very pungent odor and is acrid to the skin. What is the composition of carbureted hydrogen? its general characters? mode of occurrence in nature? What is said of Fredonia? Mention the characters of phosphureted hydrogen; the characters of sulphureted hydrogen; its mode of occurrence. What is said of muriatic acid? 7* 78 WATER. It is rapidly dissolved by water. If passed into a solution of nitrate of silver, it produces a white precipitate which soon blackens on exposure. It is given out occasionally by volcanoes.* CLASS II.-WATER. Water (oxyd of hydrogen) is the well known liquid of our streams and wells. The purest natural water is obtained by melting snow, or receiving rain in a clean glass vessel; but it is absolutely pure only when procured by distillation. It consists of hydrogen 1 part by weight, and oxygen 8 parts. It becomes solid at 32~ Fahrenheit, (or 0~ Centigrade) and then crystallizes, and constitutes ice or snow. Flakes of snow consist of a congeries of minute crys~ tals, and stars like the annexed figure may > E7_ often be detected with a glass. Various other allied forms are also assumed. The rays meet at an angle of 60', and the branchlets pass off at the same angle with perfect regularity. The density of water is greatest at 39' 1 F.; below this it expands as it approaches 320, owing to incipient crystallization. It boils at 212 F. A cubic inch of pure water at 60' F. and 30 inches of the barometer, weighs 252'458 grains. A pint, United States standard measure, holds just 7342 troy grains of water, which is little above a pound avoirdupois (7000 grains troy.) Water as it occurs on the earth, contains some atmospheric air, without which the best would be unpalatable. This air, with some free oxygen also present, is necessary to the life of water animals. In most spring water there is a minute proportion of salts of lime, (sulphate, chlorid or carbonate,) often with a trace of common salt, carbonate of magnesia and some alumina, iron, silica, phosphoric acid, carbonic acid, and certain vegetable acids. These impurities constitute usually from J- to 10 parts, in 10,000 parts by weight. The Long Pond water, used in Boston, Of what does water consist? What is said of snow and ice? What of the density of water? its boiling temperature? the weight of a pint? What are the usual impurities of common spring or river water? * Carbonic acid and sulphurous acid gases, are described, one under carbon, and the other under sulphur. GASES CONTAININ-G HYDROGEN. 79 contains about ~ a part in 10,000; the Schuylkill of Philadelphia, about 1 part in 10,000; the Croton, used in New York city, 1 to 1~ parts in 10,000. In the Schuylkill water the constituents of the 1 part of solid ingredients were, chlorid of sodium 1'47, chlorid of magnesium 0'094, sulphate of magnesia 0'57, silica 0'8, carbonate of lime 18'72, carbonate of magnesia 3'51, carbonate of soda and loss 16'44.* The water towards the surface is always purer than that below. Sea water contains 32 to 37 parts of solid substances in solution in 1000 parts of water. The largest amount in the Atlantic, 36-6 parts, is found under the equator, away from the land or the vicinity of fresh water streams; and the smallest in narrow straits, as Dover Straits where there are only 32'5 parts. In the Baltic and the Black Sea, the proportion is only one-third that in the open ocean. Of the whole, onehalf to two-thirds is common salt (chlorid of sodium.) The other ingredients are magnesian salts, (chlorid and sulphate,) amounting to four-fifths of the remainder, with sulphate and carbonate of lime, and traces of bromids, iodids, phosphates and fluorids. The water of the British channel affords, water 964'7 parts in 1000, chlorid of sodium 27'1, chlorid of pot. assium 0'8, chlorid of magnesium 3'7, sulphate of magnesia 2'30, sulphate of lime 1'4, carbonate of lime 0'03, with some bromid of magnesium, and probably traces of iodids, fluorids and phosphates. The bitter taste of sea water is owing to the salts of magnesia present. The waters of the Dead Sea contain 200 to 250 parts of solid matter in 1000 parts, (or 20 to 25 per cent.,) including 7 to 10 per cent. of common salt, the same proportion of magnesian salts principally the chlorid, 24 to 3~ per cent. of carbonate and sulphate of lime, besides some bromids and alumina. The density of these waters is owing to this large proportion of saline ingredients. The brine springs of New York and other states south and west, are well known sources of salt, (see bevond under common salt.) Many of the springs afford bromine, and large quantities of it are manufac. tured for making daguerreotype plates and other purposes. What proportion of solid substances in sea water, and of this what proportion is common salt? What proportion magnesiansalts? What is the bitter taste of sea water owing to? * Chem. Exam. by B. Silliman, Jr, Jour. Sci., ii ser., ii, 218. 80 CARBON. Mineral waters vary much in constitution. They often contain carbonate of iron, like those of Saratoga and Balls' town, and are then called chaiybeale waters, from the ancient name for iron or steel, chalybs, derived from the name of a country on the Baltic. The water of Congress Spring, ac. cording to Dr. Steel, contains in a pint, chlorid of sodium 48'1, bicarbonate of magnesia 12,0, carbonate of lime 12'3, carbonate of iron 0'6, silica 0'2, iodid of sodium nearly 0.5, with a trace of bromid of potash; of carbonic acid 39'0 cubic inches and nearly 1 cubic inch of atmospheric air. Minute traces of salts of zinc and arsenic, lead, copper, antimony and tin, have been found in some waters. Whatever is soluble in a region through which waters flow, will of course be taken up by them, and many ingredients are soluble in minute proportions, which are usually described as insoluble. CLASS III.-CARBON AND COMPOUNDS OF CARBON. Carbon occurs crystallized in the diamond. In a massive form, and more or less pure state, it constitutes the various kinds of mineral coal. Combined with hydrogen, or hydrogen and oxygen, it forms bitumen, amber, and a number of native mineral resins. DIAMOND. Monometric. In octahedrons, dodecahedrons and more complex forms. Faces often curved, as in the annexed figures. Cleavage octahedral; highly perfect.! 92 3 4 Color white or colorless; also yellowish, red, orange, What are chalybeate waters? What is the difference between the diamond and charcoal? What is the crystallization of the diamond? What other characters are mentioned? THE DIAMOND. 81 green, brown or black. Luster adamantine. Transparent; translucent when dark colored. H = 10. Gr = 3483'55.' Comnposition. Pure carbon. It burns and is consumed at a high temperature, producing carbonic acid gas. Exhibits vitreous electricity when rubbed. Some specimens exposed to the sun for a while, give out light when carried to a dark place. Strongly refiacts and disperses light. Dif. Diamonds are distinguished by their superior hardness; their brilliant reflection of light and adamantine luster; their vitreous electricity when rubbed, which is not afforded by other gems unless they are polished; and by the prac-. ticed ear, by means of the sound when rubbed together. Obs. Diamonds occur in India, in the district between Golconda and Masulipatam, and near Parma, in Bundelcund, where some of the most magnificent specimens have been found; also on the Mahanuddy, in Ellore. In Borneo, they are obtained on the west side of the Ratoos mountain, with gold and platina. The Brazilian mines were first discovered in 1728, in the district of Serra do Frio, to the north of Rio de Janeiro; the most celebrated are on the river Jequitinhonha, which is called the Diamond river, and the Rio Pardo; twenty-five to thirty thousand carats are exported annually to Europe from these regions. In the Urals of Russia they had not been detected till July, 1829, when Humboldt and Rose were on their journey to Siberia. The river Gunil, in the province of Constantine, in Africa, is reported'to have afforded some diamonds. In the United States, the diamond has been met with, in Rutherford county, North Carolina, (fig. 4,) and Hall county, Georgia. The original rock in Brazil appears to be either a kind of laminated granular quartz called itacolumite; or a ferruginous quartzose conglomerate. The itacolumite occurs in the Urals, and diamonds have been found in it; and it is also abundant in Georgia and North Carolina. In India, the rock is a quartzose conglomerate. The origin of the diamond has been a subject of speculation, and it is the prevalent opinion that the carbon, like that of coal, is of vegetable origin. Some crystals have been found with black uncrystallized particles or seams within, looking like coal; and this fact has been supposed to prove their vegetable origin. How is the diamond distinguished 1? What are its principal localities? 82 CARBON. Diamonds with few exceptions are obtained fiom alluvial washings. In Brazil, the sands and pebbles of the diamond rivers and brooks (the waters of which are drawn off in the dry season to allow of the work) are collected and washed under a shed, by a stream of water passing through a succession of boxes. A negro washer stands by each box, and inspectors are stationed at intervals. When a diamond is found weighing 17~ carats, the negro is entitled to his liberty. The largest diamond of which we have any knowledge is mentioned by Travernier, as in the possession of the Great Mogul. It weighed originally 900 carats, or 2769'3 grains, but was reduced by cutting to 861 grains. It has the form and size of half of a hen's egg. It was found in 1550, in the mine of Colone. The diamond which formed the eye of a Braminican idol, and was purchased by the Empress Catha. iine iI. of Russia from a French grenadier who had stolen it, weighs 193 carats, and is as large as a pigeon's egg. The Pitt or regent diamond is of less size, it weighing but 136'25 carats, or 4194 grains; but on account of its unblemished transparency and color, it is considered the most splendid of Indian diamonds. It was sold to the Duke of Orleans by Mr. Pitt, an English gentleman, who was governor of Bencolen, in Sumatra, for ~130,000. It is cut in the form of a brilliant, and is estimated at ~125,000. Napoleon placed it in the hilt of his sword of state. The Rajah of Mattan has in his possession a diamond from Borneo, weighing 367 carats. The diamonds of Brazil are seldom large. Maure mentions one of 120 carats, but they rarely exceed 18 or 20. The famous diamond, weighing 1680 carats, belonging to the emperor of Brazil, is supposed to be a topaz. Diamonds are valued according to their color, transparency and size. When limpid (of pure water) and no ex. traordinary magnitude, the value of a wrought diamond is estimated by first ascertaining the weight in carats.* The How are diamonds obtained? How are diamonds valued? * A carat is a conventional weight, and is divided into 4 grains, which are a little lighter than 4 grains troy; 74 1-16 carat grains are equal to 72 troy grains. The term carat is derived from the name of a bean in Africa, which, in a dried state, has long been used in that country for weighing gold. These beans were early carried to India, and were employed there for weighing diamonds. THE DIAMOND. 83 rule given is as follows: double the weight in carats, and multiply the squaie of the product by ~2. Thus a wrought diamond weighing 1 carat, would be worth ~8; one of 4 carats, ~128; one of 10 carats, ~800. A.Jove 20 carats, the prices rise much more rapidly. A flaw, however mi. nute, or the slightest smokiness, diminishes very much the value. The average price of rough diamonds, of first quality, of 1 carat, is ~2; of 2 carats, ~8, since it loses half its weight in cutting, and becomes then one of 1 carat wrought. The rule just given is scarcely regarded in market, as so much depends upon the purity of water. In different countries, moreover, the standard of taste as regards diamonds is very different, the market in England demanding the very first quality, while in other countries a somewhat inferior kind satisfies the purchaser. The rose diamond is more valuable than a snow-white diamond, owing to the great beauty of its color and its rarity. The green diamond is much esteemed on account of its color. The blue is prized only for its rarity, as the color is seldom pure. The black diamond, which is uncommonly rare and without beauty, is highly prized by collectors. The brown, gray and yellow varieties are of much less value than the pure white or limpid diamond. The diamond is cut by taking advantage of its cleavage, and also by abrasion with its own powder and by friction with another diamond. The flaws are first removed by cleaving it; or else by sawing it with an iron wire, which is covered with diamond powder-a tedious process, as the wire is generally cut through after drawing it across five or six times. After the portion containing flaws has thus been cut off, the crystal is fixed to the end of a stick, in a strong cement, leaving the part projecting which is to be cut; and another being prepared in the same manner, the two are rubbed together till a facet is produced. By changing the position, other facets are added in succession till the required form is obtained. A circular plate of soft iron is then charged with the powder produced by the abrasion, and this, by its revolution, finally polishes the stone. To complete a single facet often requires several hours. Diamonds were first cut in Europe, in 1456, by Louis Berquen, a citizen of Bruges; How are diamonds cut? 84 CARBON. but in China and India, the art of cutting appears to have been known at a very early period. By the above process, diamonds are cut into brilliant, rose and table diamonds. The brilliant has a crown or upper part, consisting of a large central eight-sided facet, and a series of facets around it; and a collet, or lower part, of pyramidal shape, consisting of a series of facets, with a smaller series near the base of the crown. The depth of a brilliant is nearly equal to its breadth, and it therefore requires a thick stone. Thinner stones, in proportion to the breadth, are cut into rose and table diamonds. The surface of the rose diamond consists of a central eight-sided facet of small size, eight triangles, one corresponding to each side of the table, eight trapeziums next, and then a series of sixteen triangles. The collet side consists of a minute central octagon, surrounded by eight trapeziums, corresponding to the angles of the octagon, each of which trapeziums is subdivided by a salient angle into one irregular pentagon and two triangles. The table is the least beautiful mode of cutting, and is used for such fiagments as are quite thin in proportion to the breadth. It has a square central facet, surrounded by two or more series of four-sided facets, corresponding to the sides of the square. Diamonds have also been cut with figures upon them. As early as 1500, Charadossa cut the figure of one of the Fathers of the church on a diamond, for Pope Julius II. Diamonds are employed for cutting glass; and for this purpose only the natural edges of crystals can be used, and those with curved faces are much the best. Diamond dust is used to charge metal plates of various kinds for jewelers, lapidaries and others. Those diamonds that are unfit for working, are sold for various purposes, under the name of bort. Fine drills are made of small splinters of bort, which are used for drilling other gems, and also for piercing holes in artificial teeth and vitreous substances generally. The diamond is also used for lenses for microscopes. When ground plano-convex, they have but slight chromatic aberration, and consequently a larger field, and but little loss of light, compared with similar lenses of other materials. They often have an irregularity of structure when perfectly What are the three forms usually given the diamond? For what purposes are diamonds used? MINERAL COAL. 85 pellucid, which unfits them for this purpose, and such lenses therefore are seldom made. MINERAL COAL. Massive. Color black or brown, opaque. Brittle or sectile. H -1- 2'5. Gr1= 12- 175. Conmposition. Carbon, with usually a few per cent. of silica and alumina, and sometimes oxyd of iron; often contains a large proportion of bitumen. The bituminous varie. ties burn with a bright flame and bituminous odor; while those destitute of bitumen afford only a pale blue flame, arising from the decomposition of the water present and the formation of the gas called carbonic oxyd. VARIETIES.-1. Without bitumen. Anthrac;te. Anthracite (called also glance coal and stone coal) has a high luster, and is often iridescent. It is quite compact and hard, and has a specific gravity from 1'3 to 1'75. It usually contains 80 to 90 per cent. of carbon, with 4 to 7 of water, the rest consisting of earthy impurities. There is often some bitumen present, in which case it burns with considerable flame. Besides the use of anthracite for fuel, it is often made into inkstands, small boxes, and other articles, which have a high polish, and fine specimens of this kind of ware may be ob. tained in Philadelphia. 2. Bituminous varieties. Bituminous coal varies much and indefinitely in the amount of bitumen it contains, and there is a gradual pas. sage in its varieties into varieties of anthracite. It is softer than anthracite and less lustrous. The specific gravity does not exceed 1'5. Pitching or caking coal, as it is distinguished in England, at first breaks when heated, into small pieces, which, on raising the heat, again unite into a solid mass. Its color is velvet or grayish black. It burns readily with a lively yellow flame, but requires frequent stirring to prevent its cakling, and so clogging the fire. The principal beds at Newcastle, England, afford this kind of coal. Cherry coal resembles pitch coal in appearance, but does not soften and cake. It Of what does mineral coal consist? How does anthracite differ from other varieties? 8113 CARBON. is very brittle, and in mining there is consequently mYIUch waste. It burns with a clear yellow flame. It occurs at the Glasgow coal beds, and is named from its luster and beauty. The splint coal (or hard coal) of the same region is harder than the cherry coal. Cannel coal is very compact and even in texture, with little luster, and breaks with a large conchoidal fracture. It takes fire readily, and burns without melting with a clear yellow flame, and has hence been used as candles-whence the name. It is often made into inkstands, snuff-boxes and other similar articles. Brown coal, wood coal, lignite, are names of a less perfect variety of coal, usually having a brownish black color, and burning with an empyreumatic odor. It has often the structure of the original wood. The term brown coal is, how. ever, applied generally to any coal more recent in origin than the era of the great coal beds of the world, although it may not have any distinct remains of a woody structure, ox burn with an empyreumatic odor. The name lignite has sometimes the same general application, though without strict propriety. Jet resembles cannel coal, but is harder, of a deeper black color, and has a much higher luster. It receives a brilliant polish, and is set in jewelry. It is the Gagates of Dioscor, ides and Pliny, a name derived from the river Gagas, in Syria, near the mouth of which it was found, and the origin of the term jet, now in use. Obs. Mineral coal occurs in extensive beds or layers, interstratified with different rock strata.- The associate rocks are usually clay shales (or slaty beds) and sandstones; and the sandstones are occasionally coarse grit rocks. There are sometimes also beds of limestone alternating with the other deposits. In a vertical section through the coal measures-as the series of rocks and coal seams are usually called —there may be below, sandstones and shales in alter. nating layers, or sandstones alone and then shales; there may next appear upon the shale a bed or layer of coal, one, two or even thirty feet thick; then above the coal, other layers of shale and sandstone; and then another layer of coal; again shale and sandstones in various alternations, or What is cannel coal? brown coal or lignite? jet? How do beds of coal occur, and what are the associated rocks? MINERAL COAL. 87 perhaps layers of limestone; and then a third bed of coal, and so on. By such alternations the series is completed. Immediately in the vicinity of the coal, the rock is generally rather a shale than a sandstone, and these shales are usually full of impressions of leaves and stems of plants. The clay shales are sometimes quite soft and earthy, and of a light clay color; but in most coal regions they are hard and firm, with a brownish or black color, in the vicinity of the coal layer. The sandstones are either of a grayish, bluish, or reddish color. These various layers constituting coal beds, are sometimes nearly or quite horizontal in position, as in New Holland and west of the Appalachians. They are very often much tilted, dipping at various angles and sometimes verti. cal, as is generally the case throughout central Pennsylvania; and in some cases the beds are raised in immense folds, as the leaves of a book may be folded, by a sidewise pressure. They are very commonly intersected by fractures, along which the coal seam on one side is higher or lower than on the other, owing to a dislocation, (then said to be faulted); and miners working in a bed for a while, in such a case, find it to terminate abruptly, and have to explore above or below for its continuation. These are points of great importance in the mining of coal. There is no infallible indication of the presence of coal distinguishable in the mineral nature of rocks; for just such rocks as are here described occur where no coal is to be found, and where none is to be expected. The presence of fossil leaves of ferns, and of plants having jointed stems or a scarred or embossed surface, in the shales or sandstone, is a useful hint; the discovery of the coal itself a much better one. The geologist ascertains the absence of coal from a region by examining the fossils in the rocks; these fossils being different in rocks of different ages, they indicate at once whether the beds under investigation belong to what is called the coal series. If they contain certain trilobites, and other species which are found only in more ancient rocks, there is no longer a doubt that coal is not to be obh. tained in any workable quantities; and he arrives at the same conclusion if the remains are those of more recent What is said of the position of the beds? How do the rocks indicate whether coal is to be expected in a region or not? 88 CARBON. rocks, such as fossil fish of certain genera, or the remains or traces of birds or quadrupeds, or of such species of shells as never occur as low in the rocks as true coal beds. But if the fossils are such as have been described as characterizing a coal series, there is then reason for exploration. It is impossible in this place to give such knowledge as will be practically useful. The inquirer must refer to treatises on geology, or better to the' practical geologist, whose judgment in such questions might often have saved much useless mining and wasted expenditure. Mineral coal is very widely distributed over the world. England, France, Spain, Portugal, Belgium, Germany, Austria, Sweden, Poland and Russia, have their beds of mineral coal. It is also abundant in India, China, Madagascar, Van Dieman's Land, Borneo and other East India Islands, New Holland, and at Conception in Chili. But no where is the coal formation more extensively displayed than in the United States, and in no part of the world are its beds of greater thickness, more convenient for working, or more valuable in quality. There are four extensive areas occupied by this formation. One of these areas commences on the north, in Pennsylvania and southeastern Ohio, and sweeping south over western Virginia and eastern Kentucky and Tennessee, to the west of the Apalachians, or partly involved in their ridges, it continues to Alabama near Tuscaloosa, where a bed of coal has been opened. It has been estimated to cover 63,000 square miles. It embraces several isolated patches in the eastern half of Pennsylvania. A second coal area (the Illinois) lies adjoining the Mississippi, and covers the larger part of Illinois, the western part of Indiana, and a small northwest part of Kentucky; it is but little smaller than the preceding. A third occupies a portion of Missouri west of the Mississippi. A fourth covers the central portion of Michigan. Besides these, there is a smaller coal region (a fifth) in Rhode Island, which appears near Portsmouth, not far from the railroad to Boston, and also in Mansfield, Massachusetts. Out of the borders of the United States, on the northeast, commences a sixth coal area, that of Nova Scotia and New Brunswick, which covers 10,000 square miles, What is said of the distribution of coal over the globe? 7 ow many coal areas are there in the United States, and what their positions? What is said of the Nova Scotia and New Brunswick coal beds? MIINERAL COAL. 89 2500 square miles of which are in Nova Scotia. At Cape Breton is still another field of coal. The coal of Rhode Island and eastern Pennsylvania is anthracite. Going west in Pennsylvania, the anthracite becomes more and more bituminous; and at Pittsburg, at its western extremity, as also throughout the western states, it is wholly of the bituminous kind. The Rhode Island variety is so hard and compact and fiee from all volatile ingredients, that for many years it had been deemed unfit for use. The anthracite of eastern Pennsylvania affords 3 to 6 per cent. of aqueous vapor, and 1 to 4 per cent. of volatile combustible matter. In the Bradford coal field, lying near the eastern limits of the bituminous coal deposits, Prof. Johnson obtained 1 to 8 per cent. of moisture, 9 to 15 per cent. of inconden. sable gas, 5 to 17 of earthy matter, and 62 to 75 of carbon. In the bituminous coal of the Portage railroad, Cambria county, Penn., he obtained 18'2 per cent. of volatile combustible matter; in that of Caseyville, Ky., and Cannelton, Indiana, 30 to 34 per cent.; and in a coal from Osage river, Missouri, 41'35 per cent. The general fact that the proportion of bitumen increases as we go westward, is here well exhibited. Some of these results, derived from an extensive series of experiments, are thus averaged by Prof. Johnson: TVol. Combustible Ashes and Fixed os latter. I Clinker. Carbon. Pennsylvania anthra-' 1'34 3'84 7'37 87'45 cites, Maryland free burn- 125 1580 994 7301 ing bituminous coal Pennsylvania free burning bituminous 0'82 17'01 1335 68'82 coal, ) Virginia bituminous, 1 64 36 63 10 74 50 99 Cannelton, Indiana, l 2'20 33'99 4'97 58'44 bituminous, It has also been shown that this fact is connected with the geological condition of the country, the anthracite occurring in the east where the rocks are variously uplifted and thrown out of position by subterranean forces, evincing also other What is the relative geographical position of the anthracite and bituminous coal in the United States? What has probably made the difference in these two kinds of coal? 8* 90 CARBON. effects of heat besides this debituminisation of the coal; while the bituminous coal occurs where such disturbances of the rocks have not taken place: and the amount of bitumen increases as we recede from the region of greatest disturbance. The heat and attendant siliceous solutions have therefore been the means of giving unusual hardness to the Rhode Island coal. Owing to the various upliftings or fobldings of the strata and subsequent denudations, the beds are often exposed to view in the sides of hills or ridges, and the coal in Pennsylvania is in most cases rather quarried out than mined. The layers are at times 20 to 35 feet thick, without any slaty seams, and the excavations appear like immense caverns, whose roofs are supported by enormous columns of coal, 66 into which a coach and six might be driven and turned again with ease." Besides the great coal beds of the coal era, as it is significantly called, there are small beds, sometimes workable, of a more recent date. The bed near Richmond, Va., belongs to a subsequent period; there are also beds in Yorkshire, and at Brora in Sutherland. Tertiary coal occurs in Provence, and also in Oregon on the Cowlitz. These beds of more recent coals are seldom sufficiently extensive to pay for working, and are often much contaminated by pyrites. The amount of anthracite worked in 1820, in Pennsylvania, was only 380 tons; in 1847, it amounted to more than 3,000,000 tons; and the whole amount of both anthracite and bituminous coal worked in that state, in 1847, was not less than 5,000,000 tons. In Great Britain, the annual amount of coal mined is about 35,000,000 of tons. The uses of mineral coal are well known. The Pennsylvania anthracite was first introduced into blacksmithing in 1768 or 1769, by Judge Obadiah Gore, a blacksmith, who early left Connecticut for Wilkesbarre. It is now employed in smelting iron ores, and for nearly every purpose in the arts for which charcoal was before employed. The formation of coke from pit coal, for smelting iron, is done in close furnaces or ovens. After heating up, the coal (about two tons) is thrown in at a circular opening at top, and remains for 48 hours; the doorway is gradually closed to shut off the air as the combustion increases, and finally the atmosphere is wholly shut off, and in this condition it How is coke prepared I GRAPHIITE. 91 remains for 12 hours. The volatile matter is thus expelled, and the cokes produced are ponderous, extremely hard, of a light gray color, and having a metallic luster. To make another kind of coke, like charcoal, the pit coal is placed in a receptacle more like a baker's oven, and the air has more free access. Both of these kinds of coke are used in smelting. GRAPHITE. —Plumbago. Occasionally in six-sided prisms, with a transversely foli. ated structure. Usually foliated, and massive; also granular and compact. Luster metallic, and color iron black to dark steel gray. Thin lamine flexible. H = 1-2. Gr=-209. Soils paper, and feels greasy. Composition. 90 to 96 per cent. of carbon, with the rest iron. Some specimens from Brazil contain scarcely a trace of iron. It is often called carburet of iron, but is not a chemical compound. It is infusible before the blowpipe, both alone and with reagents; it is not acted upon by acids. Dif. Resembles molybdenite, but differs in being unaffected by the blowpipe and acids. The same characters distinguish the granular varieties from any metallic ores they resemble. Obs. Graphite (called also black lead) is found in crystalline rocks, especially in gneiss, mica slate and granular limestone; also in granite and argillite, and rarely in greenstone. Its principal English locality is at Borrowdale, in Cumberland. Ure observes that this mineral became so common a subject of robbery, a century ago, as to have enriched many living in the neighborhood; a body of miners would break into the mine and hold possession of it for a considerable time. The place is now protected by a strong building, and the workmen are required to put on a working dress in an apartment on going in and take it off on coming out. In an inner room two men are seated at a large table assorting and dressing the graphite, who are locked in while at work and watched by the steward from an adjoining room, who is armed with two loaded blunderbusses. This is deemed necessary to check the pilfering spirit of the Cum. What is the appearance of graphite? What is its prominent characteristic? its composition? Where does it occur? Where is it worked in England? 92 G:RAPHITE. berland mountaineers. In some years the net produce of the six weeks' annual working of the mine, has amounted to ~40,000. In the United States, graphite occurs in large masses in veins in gneiss at Sturbridge, Mass. It is also found in North Brookfield, Brimfield and Hinsdale, Mass.; at Roger's rock, near Ticonderoga; near Fishkill landing in Dutchess county; at Rossie, in St. Lawrence county, and near Amity, in Orange county, N. Y.; at Greenville, L. C.; in Corn. wall, near the iHousatonic, and in Ashford, Ct.; near Attle. boro, in Buck's county, Penn.; in Brandon, Vermont; in Wake, North Carolina; on Tyger river, and at Spartanburg, near the Cowpens furnace, South Carolina. For the manufacture of pencils the granular graphite has been preferred, and it is this character of the Borrowdale graphite which has rendered it so valuable. At Sturbridge, Mass., it is rather coarsely granular and foliated, and has been extensively worked; the mine yields annually about 80 tons of graphite. The mines of Ticonderoga and Fish. kill landing, N. Y.; of Brandon, Vt.; and of Wake, North Carolina, are also worked; and that of Ashford, Ct., for. merly afforded a large amount of graphite, though now the works are suspended. The material for lead pencils, when of the finest quality, is first calcined and then sawn up into strips of the requisite size and commonly set in wood, (usually cedar,) as they ap. pear in market. It is much used now in small cylinders without wood for ever.pointed pencil cases. Graphite of coarser quality, according to a French mode, is ground up fine and calcined, and then mixed with the finest levigated clay, and worked into a paste with great care. It is made darker or lighter and of different degrees of hardness, by varying the proportion of clay and the degree of calcination to which the mixture is subjected; and the hardness is also varied by the use of saline solutions. Lampblack is sometimes addded with the clay. A superior method in use at Taunton, Mass., where the Sturbridge graphite is extensively employed, consists in finely pulverising it, and then by a very heavy pressure ob. tained by machinery, condensing it into thin sheets. These How are the best lead pencils made? How are they manufactured from the Sturbridge bed 1 AMBER. 93 sheets are then sawn up of the size required. The pencil is pure graphite, and the foliated variety is preferred on account of its being freer from impurities. Graphite is extensively employed for diminishing the friction of machinery; also for the manufacture of crucibles and furnaces, and as a wash for giving a gloss to iron stoves and railings. For crucibles it is mixed with half its weight of clay. CARBONIC ACID. Carbonic acid is the gas that gives briskness to the Sara. toga and many other mineral waters, and to artificial soda water. Its taste is slightly pungent. It extinguishes com-. bustion and destroys life. Composition: carbon 27'65, oxygen 72'35.Besides occurring in mineral waters, it is common about some volcanoes. The Grotto del Cane (Dog cave) near Naples, is a small caverh filled to the level of the en. trance with this gas. It is a common amusement for the traveler to witness its effects upon a dog kept for the purpose. He is held in the gas a while and is then thrown out apparently lifeless; in a few minutes he recovers himself, picks up his reward, a bit of meat, and runs, off as lively as ever. If continued in the carbonic acid gas a short time longer life would have been extinct. Carbonic acid combined with lime forms carbonate of lime or common limestone; with oxyd of iron it constitutes spathic iron, one of the common ores of iron; with oxyd of zinc, it forms calamine, the most profitable ore of zinc. It is found in combination also in various other minerals. AMBER. In irregular masses. Color yellow, sometimes brownish or whitish; luster resinous. Transparent to translucent. H= 2 —25. Gr-1 18. Electric by friction. Composition. Carbon 70'7, hydrogen 11'6, oxygen 7'8. Burns with a yellow flame and aromatic odor. Obs. Occurs in alluvium and on coasts, in masses from a very small size to that of a man's head. In the Royal Museum at Berlin, there is a mass weighing 18 pounds. On For what other purposes is it used? What is carbonic acid? Combined with lime, what does it form? What is the appearance of amber? Where does it occur? 94 MINERAL RESINS. the Baltic coast it is most abundant, especially between Konigsberg and Memel. It is met with at one place in a bed of bituminous coal; it also occurs on the Adriatic, in Poland, on the Sicilian coast near Catania, in France near Paris in clay, in China. It has been found in the United States, at Gay Head, Martha's Vineyard, Camden, N. J., and at Cape Sable, near the Magothy river, in Maryland. It is supposed with good reason to be a vegetable resin, which has undergone some change while inhumed, a part of which is due to acids of sulphur proceeding from decompo. sing pyrites or some other source. It often contains insects, and specimens of this kind are so highly prized as frequently to be imitated for the shops. Some of the insects appear evidently to have struggled after being entangled in the then viscous resin, and occasionally a leg or a wing is found some distance from the body, having been detached in the struggle for escape. Amber is the elektron of the Greeks; from its becoming electric so readily when rubbed, it gave the name electricity to science. It was also called succinum, from the Greek succum, juice, because of its supposed vegetable origin. Uses. Amber admits of a good polish and is used for or. namental purposes, though not very much esteemed, as it is wanting in hardness and brilliancy of luster, and moreover is easily imitated. It is much valued in Turkey for mouthpieces to their pipes. Amber is the basis of an excellent transparent varnish. After burning, there is left a light carbonaceous residue, of which the finest black varnish is made. Amber affords by distillation an oil called oil of amber, and also succinic acid; and as the preparation of amber varnish requires that the amber be heated or fused, these products are usually obtained at the time. MINERAL CAOUTCItOUc.-Elastic Bitumen. In soft flexible masses, somewhat resembling caoultchouc or India rubber. Color brownish black; sometimes orange red by transmitted light. Gr=0 9-1'25. Composition: carbon 85'5, hydrogen 13'3. It burns readily with a yellow flame and bituminous odor. What is said of the origin of amber? What term has it given to science? For what is amber used? What is mineral caoutchouc? xlTntRA L RESINS. 95 Obs. From a lead mine in Derbyshire, England, and a;oal mine at Montrelais. It has been found at Woodbury, Ct., in a bituminous limestone. RETIN-ITE. —Retinasphaltum. In roundish masses. Color light yellowish brown, green, red; luster earthy or slightly resinous in the fracture. Subtransparent to opaque, Often flexible and elastic when first dug up, but loses these qualities on exposure. H = 1-2'5. Gr= -1135. Composition: vegetable resin 55, bitumen 41, earthy matter 3. Takes fire in a candle and burns with a bright flame and fragrant odor. The whole is soluble in alcohol except an unctuous residue. Obs. Accompanies Bovey coal at Devonshire; also found with brown coal at Wolchow in Moravia, and near Halle. BITUMEN. Both solid and fluid. Odor bituminous. Lustei resinous; of surface of fracture often brilliant. Color black, brown or reddish when solid; fluid varieties nearly colorless and trans. parent. 1H=0-2. Gr-=08-1-2. VARIETIES: Mineral pitch or Asphaltum. The massive variety, often breaking with a high luster like hardened tar. The earthy mineral pitch includes less pure specimens. Petroleum. A fluid bitumen of a dark color, which oozes from certain rocks and becomes solid on exposure. A less fluid variety is called maltha, or mineral tar. Naphtha, or mineral oil. A limpid or yellowish fluid, lighter than water; specific gravity 07 —0'84. It hardens and changes to petroleum on exposure. It may be obtained from petroleum by heat, which causes it to pass off in vapor. Composition (f naphtha: carbon 82'2, hydrogen 14'S. The above varieties burn readily with flame and smoke. Obs. Asphaltum is met with abundantly on the shores of the Dead Sea, and in the neighborhood of the Caspian. A very remarkable locality occurs on the island of Trinidad, where there is a lake of it about a mile and half in circumference. The bitumen is solid and cold near the shores; but gradually increases in temperature and softness towards Describe bitumen. What is asphaltum? petroleum? naphtha? What is said of the asphaltum of Trinidad? the center, where it is boiling. The appearance of the solidified bitumen is as if the whole surface had boiled up in large bubbles and then suddenly cooled. The ascent to the lake from the sea, a distance of three quarters of a mile, is covered with the hardened pitch, on which trees and vegetation flourish, and here and there about Point La Braye, the masses of pitch look like black rocks among the foliage. Large deposits of asphaltum occur in sandstone in Albania. It is also found in Derbyshire, and with quartz and fluor in granite in Cornwall; in cavities of chalcedony and calc spar in Russia and other places. Naphtha issues from the earth in large quantities in Persia and the Birman empire. At Rangoon, on one of the branches of the Irawady river, there are upwards of 500 naphtha and petroleum wells which afford annually 412,000 hogsheads. In the peninsula of Apcheron on the western shore of the Caspian, naphtha rises through a marly soil in vapor, and is collected by sinking pits several yards in depth, into which the naphtha flows. Near Amiano in the state of Parma, there is an abundant spring. In the United States petroleum is common. The salines of Kenawha, Va.; Scotsville,. Ky.; Oil creek, Venango county, Penn.; Duck creek, Monroe county; near Hinsdale in Allegany county, N. Y., and Liverpool, Ohio, are among its localities. It was formerly collected for sale by the Sen. eca and other Indians; the petroleum is therefore com. monly called Genesee or Seneca oil, under which name it is sold in market. -Uses. Bitumen in all its varieties was well known to the ancients. It is reported to have been employed as a cement in the construction of the walls of Babylon. At Agrigentum it was burnt in lamps and called Sicilian oil. The Egyptians made use of it in embalming. The asphaltum of Trinidad mixed with grease or common pitch is used for pitching (technically, paying) the bottoms of ships; and it is supposed to protect them from the Teredo. Two ship loads of the pitch were sent to England by Admiral Cochrane; but it was found that the oil required to fit it for use exceeded in expense the cost of pitch in England; Where is naphtha obtained What is Seneca oil? For what is asphaltum used? MINERAL RESINS 97 and consequently the project of employing it in the arts was abandoned. Asphaltum is a constituent of the kind of black varnish called Japan. It is used in France in forming a cement for covering the roofs and lining water cisterns. A limestone, thoroughly dried, is ground up fine and stirred well in a vessel containing about one-fifth its weight of hot melted bitumen. It is then cast into rectangular moulds, which are first smeared with loam to prevent adhesion. When cold, the frame of the mould is taken apart and the block removed. Petroleum is used in Birmah as lamp oil; and when mixed with earth or ashes, as fuel. Naphtha affords both fuel and light to the inhabitants of Batku on the Caspian. Tho vapor is made to pass through earthen tubes and is inflamed as it passes out and used in cooking. The spring near Amiano is used for illuminating the city of Genoa. Both petroleum and naphtha have been employed as a lotion in cutaneous eruptions, and as an embrocation in bruises and rheumatic affections. Naphtha is often substituted for oil in oil paint, on account of its drying quickly. It is also employed for preserving the metals of the alkalies, potassium and sodium, which, owing to their tendency to unite with oxygen, cannot be kept in any liquid that contains this gas. The petroleum or Seneca oil of western New York, Pennsylvania and Ohio, as it appears in the market, is of a dark brown color, and a consistency between that of' tar and molasse s. The following are the names of other kinds of fossil resin or wax:Fossil Copal, Middletonite, Piauzite, which are resinous and nearly or quite insoluble in alcohol; Guyaquillite and Berengelite, from South America; resinous and soluble in alcohol like Retinite; Scheererite, Hatchetine, Dysodile, Hartite, Ixolyte, Ozocerite, Fichtelite, Konlite, gBranchite, found with coal, especially brown coal, and resembling wax or tallow. Idrialine is grayish or brownish black with a grayish luster, and occurs at the Cinnabar mines of Idria. CLASS IV.- SULPHIUR. Sulphur exists abundantly in the native state. It occurs combined with various metals, forming sulphurets and sul. phates; and the sulphurets especially are very common ores. The sulphuret of iron is common iron pyrites; sulphuret of copper is the yellow copper ore of Cornwall and other re. gions; sulphuret of mercury is cinnabar, the ore from which 9 98 NFATIVE SULPHtUR. mercury is mostly obtained; sulphuret of lead is galena, thel usual ore of lead. It is also sparingly met with in the con. dition of sulphuric and sulphurous acids. NATIVE SULPHUR. Trimetric. In acute octahedrons, and secon. daries to this form, with imperfect octahedral cleavage. Also massive. Color and streak sulphur yellow, sometimes orange yellow. Luster resinous. Transparent to translucent. Brittle. H- = 15-25. Gr 2o07. Native sulphur is either pure or contaminated with clay or bitumen. It sometimes contains selenium, and has then an orange yellow color. Dif. It is easily distinguished by burning with a blue flame and a sulphur odor. Obs. The great repositories of sulphur are either beds of gypsum and the associate rocks, or the regions of active or extinct volcanoes. In the valley of Noto and Mazzaro in Sicily, at Conil near Cadiz in Spain, Bex in Switzerland, and Cracow in Poland, it occurs in the former situation. Sicily and the neighboring volcanic islands, Vesuvius and the Solfatara in its vicinity, Iceland, Teneriffe, Java, Hawaii, New Zealand, Deception island, and most active volcanic regions afford more or less sulphur. The native sulphur of commerce is brought mostly from Sicily, where it occurs in beds along the central part of the south coast and to some distance inland. It is often associated with fine crystals of sulphate of strontian. It undergoes rough purification by fusion before exportation, which separates the earth and clay with which it occurs. Sixteen or seventeen thousand tons are annually imported from Sicily into England alone. Sulphur is also exported from the crater of Vulcano, one of the Lipari islands, and from the Solfatara near Naples. On the Potomac, 25 miles above Washington, fine specimens of sulphur are found associated with calc spar in a gray compact limestone. Sulphur is also found as a deposit about springs where sulphureted hydrogen is evolved, and in cavil ties where iron pyrites have decomposed. Localities of the What is the crystallization of sulphur? Mention its other characters Where is the sulphur of the arts obtained? NATIVE SULPHUR. 99 former kind are common in the state of Newv York, and of the latter in the coal mines of Pennsylvania, the gold rocks of Virginia and elsewhere. The sulphur of commerce is also largely obtained from copper and iron pyrites, it being given off during the roasting of these ores, and collected in chambers of brick work connected with the reverberatory furnace. It is afterwards purified by fusion and cast into sticks. Sulphur when cooled from fusion, or above 232~ F., crys. tallizes in oblique rhombic prisms. When poured into water at a temperature above 300 F. it acquires the consis. tency of soft wax, and is used to take impressions of gems, medals, &c., which harden as the sulphur cools. The uses of sulphur for gunpowder, bleaching, the manufacture of sulphuric acid, and also in medicines, are well known. Gunpowder contains 9 to 20 per cent.-9 or 10 per cent. for the best shooting powder, and 15 to 20 for mining powder. SULPHURIC AND SULPHUROUS ACIDS. Sulphuric acid is occasionally met with around volcanoes, and it' is also formed from the decomposition of sulphureted hydrogen about sulphur springs. It is intensely acid. Com-. position, sulphur, 40'14, oxygen 59'86. It- is said to occur in the waters of Rio Vinagro, South America; also in Java, and at Lake de Taal on Luzon in the East Indies. Sulphurous acid is produced when sulphur burns, and causes the odor perceived during the combustion. It is common about active volcanoes. It destroys life and extinguishes combustion. Composition, sulphur 50'14, oxygen 49-86. SELENIUM, ARSENIC. Selenium has close relations to sulphur. Its most striking characteristic is the horse-radish odor perceived when it is heated. It occurs in nature combined like sulphur with various metals, and these ores, called seleniets or seleniurets, are at once distinguished by the odor when subjected to the heat of the blowpipe flame. Ar-senic is also near sulphur in a chemical point of view, although metallic in luster. It forms similar compounds with the metals and metallic oxyds, which are called arseniurets and are often highly important ores. The a}rseniozrets of nickel and cobalt are the main sources of these metals. Its ores are distinguished by giving off when heated an odor resembling garlic. What is said of sulphuric acid? What is said of sulphurous acid I 100 SALTS OF AiMMONIA.k Tellurium and Osmium are other metals having chemical relationl to sulphur. They form similar compounds with the metals. They are of rare occurrence. The minerals containing the elements arsenic, selenium, tellurium and osmium, are described under Class VII, including metals and metallic ores. CLASS V. —HALOID MINERALS. 1. AMMONIA. The salts of ammonia are more or less soluble, and are entirely and easily dissipated in vapor before the blowpipe. By this last character they are distinguished from other salts. SAL AMMONIAc.-A-Muriate of Ammonia. Occurs in white crusts or efflorescences, often A-/ At\ yellowish or gray. Crystallizes in regular octahedrons. Translucent-opaque; taste sa\A A/t line and pungent. Soluble in three parts of water. Composition: ammonia 33'89, chlorine 66'11. Gives off the odor of hartshorn when powdered and mixed with quicklime. Dif. Distinguished by the odor given off when heated along with quicklime. Obs. Occurs in many volcanic regions, as at Etna, Vesuvius, and the Sandwich Islands, where it is a product of volcanic action. Occasionally found about ignited coal seams. But the sal ammoniac of commerce is manufactured from animal matter or coal soot. It is generally formed in chimneys of both wood and coal fires. In Egypt, whence the greater part of this salt was formerly obtained, the fires of the peasantry are made of the dung of camels; and the soot which contains a considerable portion of the ammoniacal salt is preserved and carried in bags to the works, where it is obtained by sublimation. Bones and other animal mat. ters are used in France, and a liquor condensed from the gas works, in England. What are general characters of the salts of ammonia? What is a distinctive character ofsal ammoniac? What is its composition? From what is it manufactured? How is it manufactured in Egypt? SALTS OF POTASH —NITER. 101 Uses. It is a valuable article in medicine, and is employed by tinmen in soldering; also, mixed with iron filings or turnings to pack the joints in steam apparatus. Ifiascagnine-Sulphate of Ammonia. In mealy crusts, of a yellowish-gray or lemon-yellow color. Translucent. Taste pungent and bitter. Composition, sulphuric acid 53'3, ammonia 22'8, water 23'9. Easily soluble in water. Occurs at Etna, Vesuvius, and the Lipari Islands. It is one of the products from the combustion of anthracite coal. Phosphate of ammonia, bicarbonate of ammonia, and phosphate of magnesia and ammonia have been found native in guano, by E. F. Teschemacher. The last is named guanite. It occurs in brilliant rhombic prisms of 1220 30'. Gr=-15. H=2. Struvite. A phosphate of ammonia and magnesia like the guanite, but containing 13 per cent. of water. It occurs in yellowish subtransparent rhombic crystals. G=1-7. H= 1. Slightly soluble in water. Found on the site of an old church in Hamburg. 2. POTASSA. NITER.-Nitrate of Potash. Trimetric. In modified right rhombic prisms. M: M about 1200. Usually in thin white subtransparent crusts, and in needleform crystals on old walls and in caverns. Taste saline and cooling. Composition: potassa 46-56, nitric acid 53'44. Burns vividly on a live coal. Dif. Distinguished readily by its taste and its vivid action on a live coal; and from nitrate of soda, which it most resembles, by its not becoming liquid on exposure to the air. Uses. Niter, called also saltpeter, is employed in making gunpowder, forming 75 to 78 -per cent. in shooting powder, and 65 in mining powder. The other materials are sulphur (12 to 15 per cent.) and charcoal, (9 to 12~ for shooting powder, and 20 for mining.) It is also extensively used in the manufacture of nitric and sulphuric acids; also for pyrotechnic purposes, fulminating powders, and sparingly in medicine. Obs. Occurs in many of the caverns of Kentucky and other Western States, scattered through the earth that forms the floor of the cave. In procuring it, the earth is lixiviated, and the lye, when evaporated, yields the saltpeter. India is its most abundant locality, where it is obtained largely for What does niter consist of? What effect is produced when it is put on a live coal? What are its uses? Where does it occur? 9* 102 SALTS OF SODA. exportation. It is there used for making a cooling mixture, an ounce of powdered niter in five ounces of water reduces the temperature 15~ F. Spain and Egypt also afford large quantities of niter for commerce. This salt forms on the ground in the hot weather succeeding copious rains, and appears in silky tufts or efflorescences; these are brushed up by a kind of broom, lixiviated, and after settling, evaporated and crystallized. In France, Germany, Sweden, Hungary and other countries, there are artificial arrangements called nitriaries or niter-beds, from which niter is obtained by the decomposition mostly of the nitrates of lime aud magnesia which form in these beds. Refuse animal and vegetable matter putrified in contact with calcareous soils produces nitrate of lime, which affords the niter by reaction with carbonate of potash. Old plaster lixiviated affords about 5 per cent. This last method is much used in France. Chlorid of potassium, or sylv ine, has been observed with salt at Saltzburg. 3. SODA. The following salts of soda are all more or less soluble they are in general distinguished by giving a deep yellow light before the blowpipe. Hardness below 3; specific gravity below 2'9. GLAUBER SALT.-Sulphate of Soda. Monoclinate. In oblique rhombic prisms. Occurs in efflorescent crusts of a white or yellowish-white color; also in many mineral waters. Taste cool, then feebly saline a1nd bitter. Composition, soda 9103, sul.acid 24-85, water 55'77. D/if. It is distinguished from Epsom salt, for which it is sometimes mistaken, by its coarse crystals, and the yellow color it gives to the blowpipe flame. Uses. It is used in medicine, and is known by the familiar name of "' salts." Ohs. On Hawaii, one of the Sandwich Islands, in a cave at Kailua, glauber salt is abundant, and is constantly forming. It is obtained by the natives and used as medicine. Glauber What is a nitriary? What effect is produced on the blowpipe flame by soda? What is its composition? How is it distinguished from Epsom salt? Where does Glauber salt occur native? CA:RBONATE OF SODA. 103 salt occurs also in efflorescences on the limestone below Genesee Falls, near Rochester, N. Y. It is also obtained in Austria, Hungary and elsewhere in Europe. The artificial salt was first discovered by a German chemist by the name of Glauber. It is usually prepared for the arts from sea water. NITRATE OF SODA. Rhombohedral; R: R:-106~ 33'. Also in crusts or efflorescences, of white, grayish and brownish colors; taste cooling. Soluble and very deliquescent. Composition: nitric acid63'40, soda36.60. Burns vividly on coal, with a yellow light. Dif. It resembles niter, (saltpeter,) but deliquesces, and gives a deep yellow light, when burning. Obso In the district of Tarapaca, the dry Pampa for an extent of forty leagues is covered with beds of this salt, mixed with gypsum, common salt, Glauber salt and remains of recent shells. The country appears to have been under the sea at no very remote period. Uses. It is used extensively in the manufacture of nitric acid or aqua fortis. NATRON.-Carbonate of Soda. Monoclinate, Generally in white efflorescent crusts, sometimes yellowish or grayish. Taste alkaline. Effloresces on exposure, and the surface becomes white and pulverulent. Composition: a simple hydrous carbonate of soda. Effervesces strongly with nitric acid. Dif. Distinguished from other soda salts by effervescing, and from Trona, by efflorescing on exposure. Obs. Abundant in the soda lakes of Egypt, situated in a barren valley called Bahr.bela-ma, about 30 miles west of the Delta. Also in lakes *at Debrezin in Hungary; in Mexico, north of Zacatecas, and elsewhere. Sparingly dissolved in the Seltzer and Carlsbad waters. Trona is a sesquicarbonate of soda. In the province of Suckena in Africa, between Tripoli and Fezzan, it forms a How does nitrate of soda differ in composition from niter? What are other peculiarities distinguishing it? For what is it used? Where does it occur native? What are the distinctive characters of carbonate of soda? 104 SALTS OF SODA. fibrous layer an inch thick beneath the soil, and several hun. dred tons are collected annually. At a lake in Maracaibo, 48 miles from Merido, it is very abundant. Uses. Carbonate of soda is used extensively in the manu. facture of soap. The powders put up for making soda water consist of this salt and tartaric acid. On mixing the two, the tartaric acid unites with the soda and the carbonic acid of the carbonate of soda escapes as a gas producing the effervescence. In Mexico, this salt (or the sesquicarbonate, trona) occurs in such abundance over extensive districts that it is employed as a flux in smelting ores of silver, especially the chlorid of silver which is a common ore. CO3MION SALT. Monometric. In cubes (fig 1) and its secondaries, as the following. Sometimes crystals have the shape of a shallow! 2 3 4 cuplike figure 4, and are called hopper shaped crystals. They were formed floating; the cup receiving its enlargement at the margin, this being the part which lay as the surface of the brine where evaporation was going on. Common salt is usually white or grayish, but sometimes plcsents rose red, yellow and amethystine tints. H=-2. Gr=2'257. Taste salin.e. Composition: chlorine 60'3, sodium 39'7. Crackles or decrepitates when heated. Dif. Distinguished by its taste, solubility, and blowpipe characters. Obs. Salt is usually associated with gypsum, and clays or sandstone. It occurs in extensive beds in Spain, in the Pyre. nees, in the valley of Cardona and elsewhere, forming hills 300 to 400 feet high; in Poland at Wieliczka; at Hall in the Tyrol, and along a range through Reichenthal in Bavaria, For what is it used? What happens when tartaric acid and carbonate of soda are mixed? What are the forms of crystals of common salt? Of what does It consist 1 Where are some of the most remarkable deposits of rock salt? COMMON SALT. 105 HIallein in Saltzburg, Hallstadt, Ischel and Ebensee in Upper Austria, and Aussee in Stiria; in Hungary at Marmoros and elsewhere; in Transylvania; Wallachia, Gallicia and Upper Silesia; at Vic and Dieuze in France; at Bex in Switzerland; in Cheshire, England; in northern Africa in vast quantities, forming hills and extended plains; in northern Persia at Teflis; in India in the province of Lahore, and in the valley of Cashmere; in China and Asiatic Russia; in South America, in Peru and the Cordilleras of New Grenada. The most remarkable deposits are those of Poland and Hungary. The former, near Cracow, has been worked since the year 1251, and-it is calculated that there is still enough salt remaining to supply the whole world for many centuries. Its deep subterranean regions are excavated into houses, chapels and other ornamental forms, the roof being supported by pillars of salt; and when illuminated by lamps and torches, they are objects of great splendor. The salt is often impure with clay, and is purified by dissolving it in large chambers, drawing it off after it has settled and evaporating it again. The salt of Norwich (in Cheshire) is in masses 5 to 8 feet in diameter, which are nearly pure, and it is prepared for use by crushing it between rollers. Beds of salt have lately been opened in Virginia in Washington county, where as usual it is associated with gypsum. The Salmon mountains of Oregon also afford rock salt. Salt beds occur in rocks of various ages:'the brines of the United States come from a red sandstone below the coal; the beds of Norwich, England, occur in magnesian limestone; those of the Vosges in marly sandstone beds of the lower secondary; that of Bex in the lias or middle secondary; that of the Carpathian Alps in the upper oolite; that of Wieliczka, Poland and the Pyrenees, in the cretaceous formation or upper secondary; that of Catalonia in tertiary: and moreover there are vast deposits that are still more re. cent, besides lakes that are now evaporating and producing salt depositions. Vast lakes of salt water exist in many parts of the world. Lake Timpanogos, or Youta, called also the Great Salt Lake, has an area of 2000 square miles, and is remarkable for its extent, considering that it is situated towards the sumWhat is said of the beds of Cracow? How is this salt purified? Where do beds occur in North America? What is said of salt lakes? 106 SALTS OF SODA. rmit of the Rocky Mountains, at an elevation of 4200 feet above the sea. The dry regions of these mountains and of the semideserts of Califbrnia abound in salt licks and lakes. There is a small spring on the Bay of San Francisco. In northern Africa large lakes as well as hills of salt abound, and the deserts of this region and Arabia abound in saline efflorescences. The Dead and Caspian seas, and the lakes of Khoordistan, are salt. Over the pampas of La Plata and Patagonia there are many ponds and lakes of salt water. The greater part of the salt made in this country is obtained by evaporation from salt springs. Those of Salina and Syracuse are well known; and many nearly as valuable are worked in Ohio and other western states. At the best New York springs a bushel of salt is obtained fiom every 40 gallons.-(Beck.) The springs of Onondaga county, New York, afforded in 1841 upwards of three millions of bushels of salt, and it is estimated that three hundred and twenty-two millions of gallons of brine were raised and evaporated during that year.-(Beck.) To obtain the brine, wells from 50 to 150 feet deep are sunk by boring. It is then raised by machinery, carried by troughs to the boilers, which are large iron kettles set in brickwork, and there evaporated by heat. As soon as the water begins to boil, the water becomes turbid from the deposit of calcareous salts which are also contained in salt waters, and are less soluble than the salt. These are removed with ladles, called bittern ladles, with the exception of what adheres firmly to the sides of the boiler. The salt is next deposited; it is then collected and carried away to drain. The liquid which remains contains a large proportion of magnesian salts, and is called bittern from the bitter taste of these salts. Some of the brine is also evaporated by exposure to the sun in broad, shallow vats. This last process is extensively employed in hot climates for making salt from sea water, which affords a bushel for every 300 or 350 gallons. For this purpose a number of large shallow basins are made adjoining the sea; they have a smooth bottom of clay, and all communicate with one an. other. The water is let in at high tide and then shut off for the evaporation to go on. This is the simplest mode, and is What is the source of the salt manufactured in the United States? How much water is necessary to procure a bushel of salt? How is the salt obtained from the brine? How much salt is aBorded by sea water, anld how is it obtained? BORAX. 107 used even in uncivilized countries, as among the Pacific Islands. It is better to have a large receiving basin for the salt water, which shall detain the mechanical impurities of the water. Martinsite is a compound of 91 per cent. of chlorid of sodium and 9 of sulphate of magnesia. It is from the salines of Stassfurth. BORAx. —Borate of Soda. Monoclinate. In right rhomboidal prisms, (see fig. 11, page 26); M: T= 106' 6'. Cleavage parallel with M per. fect. The crystals are white and transparent with a glassy luster. H=2 -25. Gr= 1716. Taste sweetish-alkaline. Composition: soda 16'37, boracic acid 36'53, water 47'10. Swells up to many times its bulk and becomes opaque white before the blowpipe, and finally fuses to a glassy globule. Obs. Borax was originally brought from a salt lake in Thibet, where it is dug in considerable masses firom the edges and shallow parts of the lakes. The holes thus made in a short time become filled again with borax. The crude borax was formerly sent to Europe under the name of tincal, and there purified for the arts. It has also been found in Peru and Ceylon. It has of late been extensively made from the boracic acid of the Tuscany lagoons by the reaction of this acid on carbonate of soda. Uses. Borax is used as a flux not only by the mineralogist in blowpipe experiments, but extensively in metallurgi. cal operations, in the process of soldering, and in the manu. facture of gems. Boracic acid. Occurs in small scales, white or yellowish. Feel smooth and unctuous. Taste acidulous and a little saline and bitter. G=1'48. Composition, boracic acid 56'38, water 43'62. Fuses easily in the flame of a candle, tinging the flame at first green. Found at the crater of Vulcano, and also at Sasso in Italy, whence it was called Sassolin. The hot vapors of the lagoons of Tuscany afford it in large quantities. The vapors are made to pass through water, which condenses them; and the water is then evaporated by the steam of the springs, and boracic acid obtained in large crystalline flakes. It What are some of the characters of borax? What is its composition? What are its effects before the blowpipe? What is it used for? Where was it originally obtained?, How is it procured in Tuscany? What is boracic acid? What is said of the boracic acid lagoons of Tuscany? 108 SALTS OF BARYTA. still requires purification, as the best thus procured contains but 50 per cent. of the pure acid. It is employed in the manufacture of borax. Boron occurs in nature also, in datholite, tourmaline and borate of lime, but these are not a sufficient source to be employed in the arts. Thenardite. Thenardite is an anhydrous sulphate of soda from Espartine in Spain. Gay-Lussite. Occurs in oblong crystals, in a lake in Maracaibo S. A.; it is a hydrous compound of the carbonates of lime and soda. Glauberite. In oblique cystals, (usually flattened, with sharp edges,) nearly transparent and yellowish-gray in color. Taste weak, slightly saline; consists of 49 per cent. of sulphate of lime and 51 of sulphate of soda. Occurs in rock salt at Villa Rubia, Spain, and also at Aussee in Upper Austria, and Vic in France. 4. BARYTA. The salts of baryta are distinguished by their high specific gravity, which ranges from 3'5 to 4'8. They resemble the salts of strontia, and some of the metallic salts. From the latter they are distinguished by giving no odor nor metallic reaction before the blowpipe, when pure. Hardness below 4. HFEAVY SPAR.-Sulphate of Baryta. Trimetric. In modified rhombic and rectangular prisms, 1 (figs. 1, 2) M: M-101~ 40'; 2 - < P: a-141~ 10'; P: a 127 18'. Crystals usually tabular. Massive varieties often coarse e lamellar; also columnar, fibrous, granular and compact. Luster vitreous; color white and sometimes tinged yellow, red, blue or brown. Transparent or translucent. H =25 — 3'5. Gr=4'3- 48. Some varieties are fetid when rubbed. Compositioz: sulphuric acid 34, baryta 66. Decrepitates before the blowpipe and fuses with difficulty. Dif. Distinguished by its specific gravity from celestine and arragonite, and also by not effervescing with acids from the various carbonates; from the metallic salts, by no metallic reaction before the blowpipe. Obs. Heavy spar is often associated with the ores of What is a striking character of the salts of baryta? How are they distinguished from salts of the metals? What are the forms of the crystals of heavy spar? What are the colors? What is the composition? SALTS OF BAIITA. 109 metals. In this way it occurs at Cheshire, Conn.; Hatfield, Mass.; Rossie and Hatmmond, New York; Perkio. men, Pennsylvania, and the lead mines of the west. At Scoharie and Pillar Point, near Sackett's harbor, are other localities. Also near Fredericksburg and elsewhere, Virginia. The variety from Pillar Point receives a fine polish and looks like marble, the colors being in bands or clouds. Uses. Heavy spar is ground up and used as white paint, and in adulterating white lead. When white lead is mixed in equal parts with sulphate of barytes it is sometimes called Venice white, and another quality with twice its weight of barytes is called Hamburgh white, and another, one-third white lead, is called Dutch white. When the barytes is very white, a proportion of it gives greater opacity to the color, and protects the lead from being speedily blackened by sulphureous vapors; and these mixtures are therefore preferred for certain kinds of painting. There are establishments for grinding barytes near New Haven, Ct., where the spar from Cheshire, Ct., Hatfield, Mass., and Virginia, is used. The iron ore or ferruginous clay usually mixed with it, is separated by digestion in large vats of dilute sulphuric acid. WITHERITE.-Carbonate of Baryta. Trimetric. In modified rhombic prisms, (fig. 8, p. 26.) M: M-118~ 30'; M: e=1490 15'. Also in six-sided prisms terminated with pyramids. Cleavage imperfect. Also in globular or botryoidal forms: often massive, and either fibrous or granular. The massive varieties have usually a yellowish or grayish white color, with a luster a little resinous, and are translucent. The crystals are often white and nearly transparent. H=3.3'75. Gr=4'29-4' 30. Brittle. Composition: baryta 77'6, carbonic acid 22'4. Decrep. itates before the blowpipe and filses easily to a translucent globule, opaque on cooling. Effervesces in nitric acid. Dif. Distinguished by its specific gravity and. fusibility from calcareous spar and arragonite; I y its action with acids from allied minerals that are not carbonates; by yield. ing no metal from white lead ore, and by not tinging the flame red, from strontianite. What are the uses of heavy spar? How is witherite distinguished from other minerals? 10 110 SALTS OF BARYTA. Obs. The most important foreign localities of withlerite are at Alstonmoor in Cumberland, and Anglezark in Lan. cashire.. Uses. This mineral is poisonous, and is used in the north of England for killing rats. The salts of baryta are made from this species: these salts are much used in chemical analysis; the nitrate affords a yellow light in pyrotechny; the prepared carbonate is a common water color. Barytocalcite occurs at Alstonmoor in Cumberland, England, in whitish oblique rhombic crystals, M: M=106Q54'. H=4. G=3'63-7. Consists of the carbonates of lime and baryta. Bromlite is a mineral of the same composition from Bromley Hil. near Alston, and from Northumberland, England. Its crystals are right rhombic prisms. Dreelite is a compound of the sulphates of baryta and lime, occurring in small white crystalsin France. Sulphato-carbonate of Baryta occurs in six-sided prisms. 5. STRONT'IA. The salts of strontia have a high specific gravity, it ranging from 3'6 to 4'0. In this respect they most resemble the salts of baryta, and they are distinguished by the same characters as the baryta salts from the salts of the metals. Hardness below 4. CELESTINE. —Sulphate of Strontia. Trimetric. In modified rhombic prisms. M: M = 104Q to 104~ 30'. Crystals sometimes flattened; often long and slender. a: a=1030 58'. Cleavage distinct parallel with M. Massive varieties: columnar M I or fibrous, forming layers half an inch or more thick with a pearly luster; rarely granular. Color generally a tinge of blue, but sometimes clear white. Luster vitreous or a little pearly; transparent to translucent. H — 3'5. Gr=-39-4. Very brittle. Composition: sulphuric acid 43'6, strontia 56'4. De. crepitates before the blowpipe, and on charcoal fuses rather easily to a milk white alkaline globule, tinging the flame red. Phosphoresces when heated. How is witherite distinguished from strontianite? What are itsuses? What is said of the salts of strontia? What is the usual color and appearance of celestine? What is the composition? SALTS OF STRONTIA. 1 1 Dif. The long slender crystals are distinguished at once from heavy spar, as the latter does not occur in such elongated forms. From all the varieties of heavy spar, it differs in a lower specific gravity and blowpipe characters; from the carbonates it is distinguished by not effervescing with the acids. Obs. A bluish celestine, in long slender crystals, occurs at Strontian island, Lake Erie; Scoharie, Lockport and Rossie, N. Y., are other localities. A handsome fibrous variety occurs at Franktown, Huntington county, Pennsylvania. Sicily affords very splendid crystallizations associated with sulphur: the preceding figure represents one of the crystals. The prisms are attached by one end, and being crowded over the surface, they are in beautiful contrast with the yellow sulphur beneath. The pale sky-blue tint so common with the mineral, gape origin to the name celestine. Uses. Celestine is used in the arts for making the nitrate of strontia, which is employed for producing a red color in fire-works. Celestine is changed to sulphuret of strontium by heating with charcoal, and then by means of nitric acid the nitrate is obtained. STRONTIANITE. —Carbonate of Strontia. Trimetric. In modified rhombic prisms. M: M = 117~ 19'. Cleavage parallel to M, nearly perfect. Occurs also fibrous and granular, and sometimes in globular shapes with a radiated structure within. Color usually a light tinge of green; also white, gray and yellowish-brown. Luster vitreous, or somewhat resinous. Transparentto translucent. H —35 —4. Gr=3'6 —372. Brittle. Composition: strontia 70'1, carbonic acid 29'9. Fuses before the blowpipe on thin edges, tinging the flame red; becomes alkaline in a strong heat; effervesces with the acids. Dif. Its effervescence with acids distinguishes it from minerals that are not carbonates; the color of the flame before the blowpipe, from witherite; and this character and the For what is celestine used? How do strontianite and celestine differ in composition? What are distingnishing characters of strantianite 1 112 SALTS OF LIMEE. fusibility, although difficult, from calc spar. Calc spar s, le times reddens the flame, but not so deeply. Obs. Strontianite occurs in limestone at Scoharie, New York, in crystals, and also fibrous and massive. Strontian in Argyleshire, England, was the first locality known, and gave the name to the mineral and the earth strontia. It occurs there with galena in stellated and fibrous groups and in crystals. Uses. This mineral is used for preparing the nitrate of strontia, which is extensively employed for giving a red color to fire-works. 6. LIME. With the exception of the nitrate of lime, none of the native salts of lime are soluble, unless in minute propor. portions. They give no odor, and no metallic reaction before the blowpipe, except such as may arise from mixture with iron or manganese. The specific gravity is below 3'2, and hardness not above 5. The few metallic salts of lime (arsenate of lime, tungstate of lime, &c.) are arranged with the metallic ores. GYPsvuM.-Sulphate of Lime. 1 Monoclinate. Usually in right'rhom- 2 boidal prisms, with beveled sides. M: T=-111014' a:a~ i43028; e:e 1 / 110 36'. Figure 2 represents a common twin (or arrow head) crystal. EmiClI}/ nently foliated in one direction and cleaving easily, affording laminme that are flexible but not elastic. Occurs also in laminated masses, often of large size; in fibrous masses, with a satin luster; in stellated or radiating forms consisting of narrow laminoe; also granular and compact. When pure and crystallized it is as clear and pellucid as glass, and has a pearly luster. Other varieties are gray, yellow, reddish, brownish, and even black, and opaque. Whence the name of the mineral and earth strontia? For what is it used? What is said of the salts of lime? What are the prominent characters of gypsum? GYPsUM. 113 H1 1'5-2, or so soft as to be easily cut with a knife. Gr=2'31 —233. The plates bend in one direction and are brittle in another. Composition: lime 32'9, sulphuric acid 46'3, water 20'8. Before the blowpipe it becomes instantly white and opaque and exfoliates, and then falls to powder or crumbles easily in the fingers. At a high heat it fuses with difficulty. No action with acids. The principal varieties are as follows: Selenite, including the transparent foliated gypsum, so called in allusion to its color and luster firom selene, the Greek word for moon. Radiated gypsum, having a radiated structure. Fibrous gypsum or satin spar, white and delicately fibrous. Snowy gypsum and alabaster, including the white or light. colored compact gypsum having a very fine grain. Dif. The foliated gypsum resembles some varieties of Heulandite, stilbite, talc and mica; and the fibrous, -looks like fibrous carbonate of lime, asbestus and some of the fibrous zeolites; but gypsum in all its varieties is readily distinguished by its softness; its becoming an opaque white powder immediately and without fusion before the blowpipe, and by not effervescing nor gelatinizing with acids. Obs. New York, near Lockport, affords beautiful selenite and snowy gypsum in limestone. At Camillus and Manlius, N. Y., and in Davidson county, Tenn., are other localities. Fine crystals of the form represented in figure 1, come from Poland and Camfield, Ohio, and large groups of crystals frorm the St. Marys in Maryland. Troy, N. Y., also affords crys. tals in clay. In the mammoth cave, Kentucky, alabaster occurs in singularly beautiful imitation of flowers, leaves, shrubbery and vines. Alabaster comes mostly from Caste. lino in Italy, 35 miles frbm Leghorn. Massive gypsum occurs abundantly in New York, from Syracuse westward to the western extremity of Genesee county, accompanying the rocks which afford the brine springs; also in Ohio, Illinois, Virginia, Tennessee, Arkansas and Nova Scotia. It is abundant also in Europe. Uses. Gypsum when burnt and ground up forms a white What is the composition of gypsum? What is alabaster? What effect is produced by heat? How is gypsum distinguished from talc, mica and other minerals? 1()0 114 GYPSUTM. powder, which, after being mixed with a little water, be. comes on drying, hard and compact. This ground gypsum is plaster of Paris, and is used for taking casts, making models, and for giving a hard finish to walls. Alabaster is cut into vases and various ornaments, statues, &c. It owes its beauty for this purpose to its snowy whiteness, translucency and fine texture. It is moreover so soft as to be cut or carved with common cutting instruments. Gypsum is ground up and used for improving soils. ANHYDRITE. —Anhydrous Sulphate of Lime. Trimetric. In rectangular prisms, cleaving easily in three directions, and readily breaking into d square blocks. The figure is a side view of a crystal; M: a= 1243 10'; M: ~a= 153~ 50'; M: e= 135~ 15'. Occurs also fibrous and lamellar, often contorted; also coarse and fine granular and compact. Color white or tinged with gray, red, or blue. Luster more or less pearly. Transparent to subtranslucent. H = 2'5 3'0. Gr=29- 3. The crystallized varieties have been called muriacite. Vulpinite is a siliceous variety containing 8 per cent. of silex, and a little above the usual hardness, (3'5.) Cbmposition: lime 41'5, sulphuric acid 58'5. It is a sul. phate of lime like gypsum, but differs in containing no water. Whitens before the blowpipe, but does not exfoliate like gypsum, and finally with some difficulty becomes covered with a friable enamel. No action with acids. Dif. Differs from gypsum in being harder and not ex. foliating when heated; from carbonate of lime and the zeolites which it sometimes resembles, in the non-action of acids, and its action before the blowpipe. Its square forms of crystallization and cleavage are also good distinguishing characters. Obs. A fine blue crystallized anhydrite occurs with gypsum and calcareous spar in a black limestone at Lockport. Foreign localities are at the salt mines of Bex in SwitWhat is plaster of Paris, and how is it used? For what is alabaster used? How is gypsum employed in agriculture.? How does anhydrite differ in composition firom gypsum'? Mention other distinguishing characters. CALCARE OUS SPR. 115 zerland, at Hall in the Tyrol, at Ischil in Upper Austria, Wieliczka in Poland and elsewhere. Uses. The vulpinite variety is sometimes cut and polished for ornamental purposes. CALCITE- Calcareous Spar-Carbonate of Lime. Rhombohedral, (fig. 1.) R: R=105~ 5'. Cleavage easy parallel with the faces of the fundamental rhombohedron. 1 2 3 4 5 Figure 1, is the fundamental rhombohedron; figure 2, is a flat rhombohedron with the lateral angles removed, sometimes called nail-head spar; figure 3, is a six-sided prism; figure 4, an acute rhombohedron; figure 5, a scalene dodecahedron, the form of the variety called dog-tooth spar. Figures 28, 28a, 30, 31, page 32; 62, 63, page 39; and 66, page 40, are other forms. Calcareous spar also occurs fibrous with a silky luster, sometimes lamellar, and often coarse or fine granular and compact. The purest crystals are transparent with a vitreous luster; the impure massive varieties are often opaque, and without luster, or even earthy. The colors of the crystals are either white or some light grayish, reddish or yellowish tint, rarely deep red; occasionally topaz yellow, rose or violet. The massive varieties are of various shades from white to black, generally dull unless polished. H1=3. Gr —25-'2-8. Composition: lime 56'3, carbonic acid 43'7: sometimes impure from mixture with iron, silica, clay, bitumen and other minerals. Infusible before the blowpipe, but gives out an intense light, and is ultimately reduced to quicklime. Effervesces,with the acids. Many varieties phosphoresce when heated. What is the fundamental form of calcite or cale spar? What are its colors and appearance? What is its composition? 116 SALTS OF LIME. This species takes on a great variety of forms and colors, and has received names for the more prominent varieties. Iceland spar.-Transparent crystalline calc spar, first brought from Iceland. Shows well double refraction. Satin spar.-A finely fibrous variety with a satin luster Receives a handsome polish. Occurs usually in veins traversing rocks of different kinds. Chalk. —White and earthy, without luster, and so soft as to leave a trace on a board. Forms mountain beds. N Rock milk.-White and earthy like chalk, but still softer, and very fragile. It is deposited from waters containing lime in solution. Calcareous tufa.-Formed by deposition from waters like rock milk, but more cellular or porous and not so soft. Stalactite, Stalagmite.-The name stalactite is explained on page 54. The deposits of the same origin that covet the floor of a cavern, are called stalagmite. They gen erally consist of different colored layers, and appear banded or striped when broken. The so-called " Gibraltar rock" is stalagmite from a cavern in the rock of Gibraltar. Limestone is a general name for all the massive varieties occurring in extensive beds. Oolite, Pisolite. —Oolite is a compact limestone, consisting of small round grains, looking like the spawn of a fish; the name is derived from the Greek ion, an egg. Pisolite, a name derived from pisum, the Latin for pea, differs from oolite in consisting of larger particles. Argentine.-A white shining limestone consisting of laminae a little waving, and containing a small proportion of silica. Fontainebleau limestone.-This name is applied to crystals, of the form in figure 4, containing a large proportion of sand, and occurring in groups. They were formerly obtained at Fontainebleau, France, but the locality is exhausted. Granular limestone.-A limestone consisting of crystalline grains. It is called also primary limestone. The coarser varieties when polished constitute the common white and clouded marbles, and the material of which marble buildings are made. The finer are used for statuary, and What is Iceland spar? Whatis chalk? How does satin spar under this species differ from that which is a variety of gypsum? What is calcareoustufa? Howarestalactites and stalagmiteformed? Whais limestone? What is oolite? What is said of granular limestone? CALCAREOUS SPAIR 117 called statuary marble. The best is as clear and fine grained as loaf sugar, which it much resembles. Compact limestone.-The common secondary limestones, breaking with a smooth surface, without any appearance of grains. The rock is very variously colored, sometimes of a uniform tint) and frequently in bands, blotches or veinings, and always nearly dull until polished. The varieties form marbles of as many kinds. Stinkstone, Anthraconite.-A limestone, either columnar or compact, which gives out a fetid odor when struck. Plumbocalcite, from Cornwall, contains 2'34 per cent. of carbonate of lead. Dif. The varieties of this species are easily distinguished by their being scratched easily with a knife, in connection with their strongly effervescing with acids, and their complete infusibility. Calc spar is not so hard as arragonite, and differs entirely in its cleavage. Obs. Crystallized calcareous spar occurs in magnificent forms in the vicinity of Rossie, New York. One crystal fiom there now at New Haven weighs 165 pounds. Some rose and purple varieties from thisjegion are very beautiful. Splendid geodes of the dog-tooth spar variety occur in lime. stone at Lockport, along with gypsum and pearl spar. Leyden and Lowville, N. Y., are other localities. Bergen Hill, N. J., affords beautiful wine-yellow crystals in amygdaloid. Argentine occurs nea'i Williamsburg and Southampton, Mass. Rock milk covers the sides of a cave at Watertown, N. Y., and is now forming. Stalactites of great beauty occur in Weir's and other caves in Virginia and the Western States; also in Ball's cave at Scoharie, N. Y. Chalk occurs in England and Europe, but has not been met with in the United States. Granular limestones are common in the Eastern and Atlantic States, and compact limestones in the middle and Western, and some beds of the former afflord excellent marble for building and some of good quality for statuary. Uses. Any of the varieties of this mineral when burnt, form quicklime. Heat drives off the carbonic acid and leaves the lime in a pure or caustic state. Some limestones contain a portion of clay disseminated throughout it, and these burn often to hydraulic lime, a kind of lime, of which a What is said of compact limestone? Hew is this species distin. guished from other species? What are the -ises of limestone? 118 SALTS OF LIfIM, cement or plaster is made that "6 sets" under water. See further, the chapter on Rocks, for the uses of limestone. ARRAGONITE, Trimetric. In rhombic prisms, (see fig. 8, page 26); M: M=116~ 10'. Cleavage parallel with M. Usually in compound crystals having the form of a hexagonal prism, with uneven or striated sides, or in stellated forms consisting of two or three flat crystals crossing one another. Also in globular and coralloidal shapes; also in fibrous seams in different rocks. Color white or with light tinges of gray, yellow, green and violet. Luster vitreous. Transparent to translucent. H-1-1 35-4. Gr —2931. In composition, it is identical with calcareous spar, and in its action before the blowpipe it differs only in falling to powder readily when heated. Effervesces also with the acids. Phosphoresces when heated. Some varieties con. tain a few per cent. of carbonate of strontia, but this is not an essential ingredient. Dif: The same distinctive characters as calcareous spar, except its crystalline film and superior hardness, and its falling to powder before the blowpipe. Obs. Arragonite occurs mostly in gypsum beds and deposits of iron ore; also in basalt and other rocks. The coralloidal forms are found in iron ore beds, and are called flos.ferri, flowers of iron. They look like a loosely intertwined or tangled white cord. The Jfos.ferri variety occurs at Lockport with gypsum; also at Edenville, at the Parish iron ore bed in Rossie, and in Chester county, Pennsylvania. Arragon in Spain affords six-sided prisms of arragonite, associated with gypsum. This locality gave the name to the species. 6. DOLOMITE-MlVagnesian Carbonate of Lime. Rhombohedral. R: R=106' 15'. Cleavage perfect parallel to the primary faces. Faces of rhom. bodedrons sometimes curved, as in the annexed figure. Often granular and massive, constitu. ting extensive beds. Color white or tinged with yellow, red, green, What are the usual forms of arragonite? Does it differ in composition from calcite? What are its colors and luster? What effect is produced by the blowpipe? DOLOMITE. 119 brown, and sometimes black. Luster vitreous, o0 a little pearly. Nearly transparent to translucent. Brittle. H3'5-4. Gr —28-2'9. Composition. Dolomite is a compound of carbonate of magnesia and carbonate of lime. The common variety con. sists of 54'2 of the latter to 45'8 of the former. Infusible before the blowpipe. Effervesces with acids, but more slowly than calc spar. The principal varieties of this species are as follows: Dolomite. —White crystalline granular, often not distinguishable in external characters fiom granular limestone, except that it crumbles more readily. Pearl spar.-This variety occurs in pearly rhombohe. drons with curved faces. Rhomb spar, Brown spar.-In rhombohedrons, which become brown on exposure, owing to their containing 5 to 10 per cent. of oxyd of iron or manganese. Miemite.-A yellowish brown fibrous variety from Miemo in Tuscany. Gurhofite.-A compact white rock, looking like porcelain and containing a few per cent. of silica. Dif. Distinctive characters, nearly the same as for calcareous spar. It is harder than that species, and differs in the angles of its crystals, and effervesces less freely; but chemical analysis is often required to distinguish them. Obs. Massive dolomite is common in the Eastern States, and constitutes much of the coarse white marble used for building. Crystallized specimens are obtained at the Quarantine, Richmond county, N. Y. Rhomb spar occurs in talc at Smithfield, R. I., Marlboro, Vt., Middlefield, Mass.; pearl spar in crystals of the above form at Lockport, Rochester, Glen's Falls; gurhofite on Hustis's farm, Phillipstown, N. Y. Dolomite was named in honor of the geologist and traveler, Dolomieu. Uses. Dolomite burns to quicklime like calc spai, and af. fords a stronger cement. The white massive variety is used extensively as marble. The magnesian lime has been sup. posed to injure soils; but this is believed not to be the case if it is air-slaked before being used. It is also employed in the manufacture of Epsom salts or sulphate of magnesia. What is the composition of dolomite? How does it differ from calcite? What are its uses? 120 SALTS OF LIVIPE. The mineral is subjected to the action of sulpha:lic acid; the sulphate of lime being insoluble is deposited, leaving the sul phate of magnesia in solution. A more economical method is to boil the calcined stone in proper proportions in bittern; the muriatic acid of the bittern takes up the lime. Ankerite. This species resembles brown spar, and like that becomes brown on exposure. The primary is a rhombohedron of 1060 12'. It consists of the carbonates of lime, magnesia, iron, and manganese. The Styrian iron ore beds and Saltzburg are some of its foreign localities. It is said. to occur in veins at Quebec and at West Springfield, Mass. 7, APATITE.-Phosphate of Lime. In hexagonal prisms. The annexed figure represents a crystal from St. Lawrence county, New York. Cleavage imperfect. Usually occurs in crystals; but occasionally massive; sometimes mammillary with a compact fibrous structure. Small crystals are occasionally transparent and colorless, but the usual color is green, often yellowish-green, bluish-green, and grayish-green; sometimes yellow, blue, reddish or brownish. Coarse crystals nearly opaque. Luster resinous, or a little oily. H=5. Gr —-3 —3-25. Brittle. Some varieties phosphoresce when heated, and some become electric by friction. Composition: phosphate of lime 92'1, fluorid of calcium 7'0, chlorid of calcium 0'9. Infusible before the blowpipe except on the edges. Dissolves slowly in nitric acid without effervescence. Its constituents are contained in the bones and ligaments of animals, and the mineral has probably been derived in many cases from animal fossils.* Asparagus stone is a translucent wine-yellow variety occurring in talc at Zillerthal in the Tyrol. Phosphorite is a massive variety from Estremadura in Spain, and Schlackenwald in Bohemia. Moroxite is a greenish-blue variety from Arendal. Eupyrchroite (Emmons) is a fibrous mammillary variety from Crown Point, Essex county, N. Y. What is the common form of apatite? is colcrs and appearance? Is it harder than calc spar? What is the principal constituent in its composition? What is a probable origin of this mineral in many cases? a Bones contain 55 per cent. of phosphate of lime, with some fluorid of calcium, 3 to 12 per cent. of carbonate of lime, some phosphate of magnesia and chlorid of sodium, besides 33 per cent. of animal matter, FLUOR SPAR. 121 Dif. Distinguished by its inferior hardness fron beryl, it being easily scratched with a knife; by dissolving in acids without effervescence from carbonate of lime and other carbonates; by its difficult fusibility, and giving no metallic reaction before the blowpipe from phosphate of lead and other metallic species. Its phosphorescence is also an important characteristic. Obs. Apatite occurs in gneiss and mica slate, granular limestone, and-occasionally in ancient volcanic rocks. The finest localities in the United States occur in granular limestone. The crystals from the limestone of St. Lawrence county, N. Y., are among the largest yet discovered in any part of the world. One from Robinson's farm measured a foot in length and weighed 18 pounds. But they are nearly opaque and the edges are usually rounded. They occur with scapolite, sphene, &c. Edenville and Amity, Orange county, N. Y., afford fine crystals from half an inch to twelve inches long. At Westmoreland, N. H., fine crystals are obtained in a vein of feldspar and quartz; also at Blue Hill bay in Maine. Bolton, Chesterfield, Chestel, Mass., are other localities. A beautiful blue variety is obtained at Dixon's quarry, Wilmnington, Delaware. The name apatite, from the Greek apatao, to deceive, was given in allusion to the mistake of early mineralogists re. specting the nature of some of its varieties. 8. FLUOR SPAR —Fluorid of Calcium, Fluate of Lime. Monometric. Cleavage octahedral, perfect. Secondary forms, the following: Rarely occurs fibrous; often compact, coarse or fine granular. Colors usually bright; white, or some shade of light green, purple, or clear yellow are most common; rarely rose-red and sky-blue; colors of massive varieties often How is apatite distinguished from beryl? how from carbonates? how from phosphate of lead? What is said of the crystalline form and cleavage of fluor spar? What is said of its colors and appearance? 11 122 SALTS OF LElME. banded. The crystals are transparent or translucent. H1 —4 Gr —314 -318. Brittle. Composition: fluorine 47-7, calcium 52'3. Phosphoresces on a hot iron, giving out a bright light of different colois; in some varieties the light is emerald green; in others, purple, blue, rose-red, pink, or an orange shade. Before the blowpipe it decrepitates, and ultimately fuses to an enamel. Pulverised and moistened with sulphuric acid, a gas is given off which corrodes glass. The name chlorophane has been given to the variety that affords a green phosphorescence. Dif. In its bright colors, fluor resembles some of the gems, but its softness at once distinguishes it. Its strong phosphorescence is a striking characteristic; and also its affording easily, with sulphuric acid and heat, a gas that corrodes glass. Obs. Fluor spar occurs in veins in gneiss, mica slate, clay slate, limestone, and sparingly in beds of coal. It is the gangue in some lead mines. Cubic crystals of a greenish color, over a foot each way, have been obtained at Muscolonge Lake, St. Lawrence county, N. Y. Near Shawneetown on the Ohio, a beautiful purple fluor in grouped cubes of large size is obtained from limestone and the soil of the region. At Westmoreland, N. H., at the Notch in the White Mountains, Blue Hill Bay, Maine, Putney, Vt., and Lockport, N. Y., are other localities. The chlorophane variety is found with topaz at Huntington, Conn. In Derbyshire, England, fluor spar is abundant, and hence it has received the name of Derbyshire spar. It is a common mineral in the mining districts of Saxony. Fluorid of calcium is also found in the enamel of teeth, in bones and some other parts of animals; also in certain parts of many plants; and by vegetable or animal decomposition it is afforded to the soil, to rocks, and also to coal beds in which it has been detected. Uses. Massive fluor receives a high polish and is worked into vases, candlesticks and various ornaments, in Derbyshire, England. Some of the varieties frbm this locality, consisting of rich purple shades banded with yellowish white, are very What is said of the phosphorescence of calc spar? Of what does it colsist? What is chlorophane? Howjs fluor spar distinguished from the gems? What are its uses? FLUOR SPAR. 123 beautiful. The mineral is difficult to work on account of be. ing brittle. It is usually turned in a lathe, and worked down first with a fine steel tool; then with a coarse stone, and afterwards with pumice and emery. The crevices which occur in the masses are sometimes concealed by filling them with galena, a mineral often found with the fluor. Fluor spar is also used for obtaining fluoric acid, which is employed in etching. To etch glass, a picture, or whatever design it is desired to etch, is traced in the thin coating of wax* with which the glass is first covered; a very small quantity of the liquid fluoric acid is then washed over it; on removing the wax, ill a few minutes, the picture is found to be engraved on the glass. The same process is used for etching seals, and any siliceous stone will be attacked with equal facility. Fluor spar is also used as a flux to aid in reducing copper and other ores, and hence the name fluor. Ilayesine or Hydrous Borate of Lime. Occurs in snowy white interwoven fibers, with gypsum and alum on the plains of Iquique, S. A. Hydroboracite. A hydrous borate of lime and magnesia resembling somewhat a white fibrous gypsum. It is of Caucasian origin. Oxalate of Lime. Observed on calc spar in small oblique crystals. Locality unknown. Nitrate of Lime. In white delicate efflorescences; deliquescent. Also in solution in some waters. The salt is formed in calcareous caverns and covered spots of earth where the soil is calcareous. It is extensively used in the manufacture of saltpeter, (nitrate of potash.) Occurs in the caverns of Kentucky and other Western States. 7. MAGNESIA. The sulphates and nitrate of magnesia are soluble, and are distinguished by their bitter taste. The other native mag. nesian salts are insoluble. The presence of magnesia when no metallic oxyds are present is indicated by a blowpipe experiment: after heating a fragment, moisten it with a solu. tion of nitrate of cobalt, and then subject it again to the heat How is glass etched by means of fluor spar? What is the origin of the name fluor? What is said of the occurrence and uses of nitrate of lime? What is the taste of soliuble salts of magnesia? What blowpipe test distinguishes them? * The best material is a mixture of bees wax and turpentine resin melted together. 124 SALTS OF MAGNESItA of the blowpipe, and it will become pale-red, and deepen in color by fusion. Specific gravity of the species in this family, below 3. Hardness of some species as high as 7. EPSOM sALT.-Sulphate of Magnesia. Trimetric. In modified rhombic prisms, (fig. 8, page 26.) M: M — 900 38'. Cleavage perfect parallel with the shorter diagonal. Usually in fibrous crusts, or botryoidal masses, of a white color. Luster vitreous-earthy. Very soluble, and taste bitter and saline. Composition: magnesia 16'7, sulphuric acid 32'4, water 50'9. Deliquesces before the blowpipe. Does not effervesce with acids. Dif. The fine spicula-like crystalline grains of Epsom salt, as it appears in the shops, distinguish it fiom Glauber salt, which occurs usually in thick crystals. Obs. - The floors of the limestone caves of the West often contain Epsom salt in minute crystals mingled with the earth. In the Mammoth Cave, Ky., it adheres to the roof in loose masses like snow-balls. It occurs as an efflorescence on the east face of the Helderberg, 10 miles from Coeymans. The fine efflorescences suggested the old name hair salt. At Epsom in Surrey, England, it occurs dissolved in mineral springs, and from this place the salt derived the name it bears. It occurs at Sedlitz, Arragon, and other places in Europe; also in the Cordilleras of Chili; and in a grotto in Southern Africa, where it forms a layer an inch and a half thick. Uses. Its medical uses are well known. It is obtained for the arts from the bittern of sea-salt works, and quite largely from magnesian carbonate of lime, by decomposing it with sulphuric acid. The sulphuric acid takes the lime and magnesia, expelling the carbonic acid; and the sulphate of magnesia remaining in solution is poured off from the sulphate of lime, which is insoluble. It is then crystallized by evaporation. MAGN-EsITE.- Carbonate of Magnesia. Rhombohedral; R: R = 101~ 22'. Cleavage rhombohedral, perfect. Often in fibrous plates the surface of which Of what does Epsom salt consist?- Where does it occur? Whence the name Epsom? CARBONATE OF MAGNESIA. 125 frequently consists of minute acicular crystals; also granular and compact and in tuberous forms. Color white, yellow. ish or grayish-white or brown. Luster vitreous; fibrous varieties often silky. Transparent to opaque. H=3-4. Gr-2.8-3. Composition: carbonic acid 51-7, and magnesia 48'3. Infusible before the blowpipe. Dissolves slowly with little effervescence in nitric or sulphuric acid. Dif. Resembles some varieties of carbonate of lime and dolomite; but effervesces more feebly in acids, does not burn to quicklime, and the light before the blowpipe is less intense. The fibrous variety is distinguished fi'om amianthus and other fibrous minerals associated with it, by its greater hardness and more vitreous luster, and from siliceous minerals gen. erally by its complete solubility in acids. Obs. Magnesite is usually associated with magnesian rocks, especially serpentine.- At Hoboken, N. J., it occurs in this rock in fibrous seams; similarly at Lynnfield, Mass.; and at Bolton, imperfectly fibrous, traversing white limestone. Uses. When abundant it is a convenient material for the manufacture of sulphate of magnesia or Epsom salt, to make which, requires simply treatment with sulphuric acid. a3RUCITE.-Hydrate of Magnesia. In foliated hexagonal prisms and plates. Structure th;t, foliated, and thin laming easily separated and translucent' flexible but not elastic. Color white and pearly, often grayish or greenish. H_=15. Gr=2'35. Composition: magnesia 69'7, water 30'3. Infusible be. fore the blowpipe, but becomes opaque and friable. Entirely soluble in the acids without effervescence. Dif. It resembles talc and g) psum, but is soluble in acids; it differs firom heulandite and stilbite, also by its infusibility. Obs. Occurs in serpentine, at Hoboken, N. J., and Richmond Co., N. Y., also at Swinaness in Unst, one of the Shetland Isles. Nemalite is a fibrous hydrate of magnesia or brucite. The following are its charicters; Of what does magnesite consist? How is it distinguished from most earthy minerals? How from calc spar? For what use is it fitted?What is the appearance of nemalite? its composition 7 its locality? 11* 126 SALTS OF MAGNESIA. Neatly fibrous and silky; fibres brittle and easily sepera. ble. Color whitish, grayish or bluish white; transparent, but becomes opaque and crumbling on exposure. H = 2. Gr-2'35 —24. Composition: magnesia 62'0; protoxyd of iron 4'6; water 28'4; carbonic acid 4'1; —(Whitney.) In the flame of a candle the fibres become opaque, brownish and rigid, and in this state easily crumble in the fingers. Phosphoresces with a yellow light when rubbed with a piece of iron. Dif. Resembles abestus or amianthus, but differs in becoming brittle before the blowpipe. Obs. Occurs in serpentine at IHoboken, N. J., in greenstone at Piermont, Rockland Co., N. Y., and Bergen Hill, N. J. Hydromagnesite. This name is given to an earthy white pul2 verulent hydrous carbonate ofmagnesia, from Hoboken, N. J. Bo0RAcITE.-Borate of M~agnesia. Monometric. Cleavage octahedral; but only in traces. Usual in cubes with only the alternate angles replaced; or P P having all replaced, but four P of them different from the oth- I er four. The crystals are translucent and seldom more than a quarter of an inch through. Color white or grayish; sometimes yellowish or greenish. Luster vitreous. H=7. Gr=2'97. Becomes electric when heated, the opposite angles of the cube becoming of opposite poles, one north and the other south. Composition:. boracic acid 62'8, magnesia 37'2. Intu. mesces before the blowpipe and forms a glassy globule, which becomes crystalline and opaque on cooling. Dif. I Distinguished readily by its form, high hardness, and pyro-electric properties. Obs. Boracite is found only with gypsum and common salt. It occurs near Luneberg in Lower Saxony, and near Kiel in the adjoining dutchy of Holstein. Nitrate of mJagnesia. Occurs in white deliquescent efflorescences, having a bitter taste, associated with nitrate of lime, in limestone cavWhat is Brucite? What is its appearance? How is it distinguished from talc, gypsum, and other minerals? What is said of the crystals of boracite? What is stated of its electric properties? What is its composition X What is its mode of occurrence? SALTS OF ALUMINA. 127 erns. It is used, like its associate, in the manufacture of saltpeter (see page 102.) Polyhalite. A brick-red saline mineral, with a weak bitter taste, occurring in masses which have a somewhat fibrous appearance. Consists of the sulphates of lime; potash and magnesia, with six per cent. of water. Wagnerite. A fluo-phosphate of magnesia, occurring in yellowish or grayish oblique rhombic prisms. Insoluble. H=I5 —55. Gr-31. From Saltzberg, Germany. Rhodizite. Resembles boracite in its crystals, but tinges the blowpipe flame deep red. Occurs with the red tourmaline of Siberia. 8. ALUMINA. The compounds of alumina may often be distinguished by a blowpipe experiment. If a fiagment of alumina after having been heated to redness be moistened with a solution of nitrate of cobalt and again heated, it assumes before fusion a blue color. This is a good test, and distinguishes aluminous from magnesian minerals, except when the oxyds of the metals are present. The sulphates, fluorids and some of the phosphates, (the salts included in this family,) are soluble with more or less difficulty, in the acids; and some of the sulphates (tho various alums) dissolve readily in water. The solution in acids takes place without effervescence, and without forming a jelly like many silicates of alumina (the zeolites, &c.) Specific gravities of the species below 3'1. Hardness of some species as high as 6. NATIVE ALUM. Monometric. Cleavage octahedral. Occurs in octahbe drons; but usually in silky fibrous masses, or in efflorescent crusts. Taste sweetish astringent. There are several kinds of native alum, dif- f / AA fering in one of the ingredients in theirconstitution, but resembling one another in crystalli- N zing in octahedrons, and in containing the ingredients in exactly the same proportions. They all contain What blowpipe experiment distinguishes alumina? What is said of the snlphates of alumina? What is the composition of the alumrns? 128 SALTS OF ALUMINA. 24 parts of water to 1 part of sulphate of alumina, and I part of some other sulphate. In potash-alum, this sulphate is a sulphate of potash. This is the common alum of the shops. The corresponding sulphate in the other alums is as fol lows:Soda-alum, sulphate of soda; Magnesia-alum, sulphate of magnesia; Ammonia-alum, sulphate of ammonia; Iron-alum, sulphate of iron; Manganese-alum, sulphate'of manganese. Besides these there is also a hydrous sulphate of alumina without any other sulphate; it is called feather-alum, and is even of more common occurrence than any of the true alums. These alums are formed from the decomposition of pyrites, in contact with clay. Iron pyrites is a compound of sulphur and iron; in decomposition, its sulphur and iron unite with oxygen derived from the moisture present, and it then be. comes sulphate of iron, or a compound of sulphuric acid and oxyd of iron. This sulphuric acid, or part of it, by uniting with the alumina of the clay rock, produces a sulphate of alumina. To form a true alum, a little potash, or soda, &co must be present in the clay. The iron of the iron alum proceeds from the pyrites which undergoes the decomposition. These compounds differ but little in taste and appearance. Obs. Potash alum and more abundantly the sulphate of alumina (or feather alum), and sulphate of alumina and iron, impregnate frequently clay-slates, which are then called aluminous slates or shales. These alum rocks are often quarried and lixiviated for the alum theycontain. The rock is first slowly heated after piling it in heaps, in order to decompose the remaining pyrites and transfer the sulphuric acid of any sulphate of iron to the alumina and thus produce the largest amount possible of sulphate of alumina. It is next lixiviated in stone cisterns. The lye containing this sulphate is afterwards concentrated by evaporation, and then the requisite proportion of potash (sulphate or muriate, alum containing potash as well as alumina) is added to the lix"What is the composition of common potash alum? What of a soda alum? What are alum shales? Whence the alum or sulphate of alumina they contain? How is alum obtain from alum shale? ALUM STONLE 129 ivium. A precipitate of alum falls which is afterwards washed and re-crystallized. The mother liquor left after the precipitation is also treated for more alum. This process is carried on extensively in Germany, France, at Whitby in Yorkshire, Hurlett and Campsie, near Glasgow, in Scotland. Cape Sable in Maryland, affords large quantities of alum annually.2 The slates of coal beds are often used to advantage in this manufacture, owing to the decomposing pyrites present. At Whitby, 130 tons of calcined schist give one ton of alum. In France, ammoniacal salts are used instead of potash, and an ammoniacal alum is formed. Soda alum has been observed at the Solfataras in Italy, near Mendoza in South America, on the island of Milo in the Grecian Archipelago. Magnesia alum forms large fibrous masses, delicately silky, near Iquique, S. A. This is the Pickeringite of' Mr. A. A. A. Hayes. Ammonia alum occurs at Tschermig in Bohemia. ALUM STONE. Rhombohedral, with a perfect cleavage parallel with a, (fig. 62;p. 39.) R: R=92~ 50'. Also massive. Color white, grayish or reddish. Luster of crystals vitreous, or a little pearly on a. Transparent to translucent. H=5. Gr= 2'58 -275. t4