—- ' DEPARTMENT OF MINES. GEOLOGICAL SURVEY. J. E. Carne, F.G.S., Government Geologist. MINERAL RESOURCES. No. 29. M : ; the TOLOGV and mining developments OF THE ARDLETHAN TIN FIELD. BY L. F. HARPER, F.G.S., Geological Surveyor. ssued under the direction of the Honorable J. C. L. Fitzpatrick, M.L.A., Minister for Mines. SYDNEY: WILLIAM APPLEGATE GULLICK, GOVERNMENT PRINTER t 71279 1919- [2s. ■ •••• • , ■■ '* * : H «? ' *V, -■ k \ i *V _ ‘ ‘ • / ■ : . ■ • I , f ■ ' ■ , *» t 1 .) - •"? • ’ -ir . .. iJ?‘ / f • I v NEW SOUTH WALES, DEPARTMENT OF MINES. GEOLOGICAL SURVEY, j. E. Carne, F.G.S., Government Geologist. MINERAL RESOURCES. No. 29. FY OF L1BRARX THE MAY 1 3 1920 GEOLOGY AND MINING DEVELOPMENTS OF THE ARDLETHAN TIN FIELD. BY L. F. HARPER, F.G.S., Geological Surveyor. Issued under the direction of the Honorable J. C. L. Fitzpatrick, M.L.A., Minister for Mines. SYDNEY: WILLIAM APPLEGATE GULLICK, GOVERNMENT PRINTER. ✓ t 71279 1910. T2.SJ I % I 3 ) f N4-T^ \^> V • A / r^. I The Geology and Mining Developments of the Ardlethan Tin Field. ■CHAPTER 1.—Introduction and Previous References, History of the Field, Acknowledgments. CHAPTER 2.—General and Detailed Geology. CHAPTER 3.—The Nature and Probable Genesis of the Ore Bodies, with Suggestions as to Prospecting. 'CHAPTER 4.—Past and Present Mining, Treatment Plants, Nature of Ore, Returns, and the Prospects of Obtaining an Adequate Supply of Sub-Artesian Water. ' 3 -j o IN 4 CHAPTER 1. INTRODUCTION AND PREVIOUS REFERENCES. The Ardlethan Tin Field has received much attention from the investing public, and has been the subject of at least three official reports, apart fiom the annual returns of the Mining Warden. As this field had not been discovered at the time Mr. J. E. Carne, F.G.S., Government Geologist, compiled his work on “ The Tin Mining Industry, and the Distribution of Tin Ores in New South Wales,”* no mention is made of it. It is the intention in this work to correlate all the information available, and supplement the original reports in the light of a detailed geological examination, and also express an opinion as to the genesis of the ore bodies, and the best means of prospecting the same. The future prospects of the field are commented upon, but it must be realised that many factors have to be considered and deductions proved, before it would be wise to dogmatise on the subject. The present writer had an opportunity of visiting the field just after the presence of tin had been proved, and the following report was supplied in 1912f:— Report on the Ardlethan Tin Field. (L. F. Harper.) “ Ardlethan is a town on the Temora-Barellan railway line, 337 miles from Sydney, and the tin occurrence is from 24 to 3 miles north-west of the town, in the parishes of Warri and Ramsay, county of Bourke. The geological formation of the country immediately in the vicinity of Ardlethan is Devonian quartzites and silicified slates, largely overlain by deposits of soil. Proceeding in a north-westerly direction, a change is soon noticeable* the soil becoming more sandy, and within 2 miles the Devonian beds give place to a granitic rock. This rock is very weathered, and it is only the more silicified portions which give rise to the low range of hills adjacent to which the tin was discovered. The granite was originally an acid type, and secondary silicification has gone on to such an extent that the present surface exposures consist almost entirely of silica. Crystallised quartz is very plentiful, and apparently the granite on cooling was sufficiently spongy to allow of a subsequent development of small quartz crystals, with veins and masses of quartz. Replacement by silica has also probably taken place to some extent. The original prospector was J. J. Keogh, who discovered tin in this locality in January of the present year. • Mineral Resources, No. 14, Department of Minos, Sydney, 1911. t Annual Report, Department of Minos, 1912, p. ISO. LOCALITY PLAN Scale 4- 4- 4- 4- -i\ 4- 4" 4- 4 4!L_ 2 Miles to/Inch j_ i ] Bald Hil l + 4- 4^t r tin belt 4- 4- 4- -f|- 4- 4- -hr 4- 4j + +/ 4- i Devonian ? 'Sandstones Quartzites Slates' Co nglom e rates e tc. Intrusive Granite * shown thus Intrusive Porphyry *» >) *j 4 - 4 - 4- - Digitized by the Internet Archive in 2018 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/geologyminingdev29harp 0 Up to the present, thirty-five authorities to enter under the Mining on Private Property Act have been issued, and all the ground surrounding the original prospector's claim has been taken up. outside of which, however, practically no work has been done. On Mr. Keogh's claim a few trenches and a shallow circular hole have been sunk, and the presence of tin proved over about a quarter of an acre of ground. The adjacent claim on the west is held by Mr. A. V. Crosby, and on its eastern boundary a shallow trench has been excavated which proved the presence of tin in small quantities, but the work done to date affords little evidence as to the extent of this occurrence. The claims adjoining the above two on the north are held by Chamberlain and Stackpool. The area held by Mr. Chamberlain covers a junction between the granite and Devonian slate, which is seen near the south-west corner. A shallow cut was made near this corner on an outcrop of massive brown iron ore, with cassiterite, but granite is showing in the bottom of the cut. A few chains further east, on the same claim, very siliceous granitic rock occurs, a sample from which was assayed and yielded metallic tin, • >72 per cent. On Apr. Stackpool’s adjoining block a shallow trench has been dug on a similar type of rock, but no tin was noticed in the tip. On Messrs. Jackson and McDonough's authority, which adjoins the prospector's at its north-east corner, a little prospecting has been done, and the following assay return was obtained from a sample taken in the north-east comer :—Xo tin detected; bismuth, 6-51 per cent. This assay proves the presence of bismuth in this locality, but no defined reef has been found, and the bismuth is apparently contained in a small lens of quartz. Xo other work has been done within the areas held, but a sample obtained from Mr. J. Hilley’s authority. Xo. 227. in parish of Ramsay, about half a mile north-west of the prospector's claim, was assayed with the following result :—Metallic tin, 4-64 per cent. The prospector's claim covers 16 acres, and work is being carried on in the centre of the lease. A shallow hole is being sunk on a belt of silicified granite traversed by quartz veins, tinstone being unevenly distributed throughout. Lumps of granular cassiterite (oxide of tin) varying in size up to 12 inches by 6 inches by 4 inches are found, and the quartz and granite are impreg¬ nated by specks, threads, and bunches of the same material. Xo crystallised tinstone was seen, it being all fine-grained and granular. A “ floor ” in the granite is being followed down with the idea that it is a footwall of the ** lode/' but cassiterite is quite as abundant outside this as it is in the channel. The dip of the " floor " is from 50 to 53 degrees to the west. A roughly-dressed sample taken across the bottom of the cut west from the floor, b assayed with the following result :—Metallic tin, 26*32 per cent. A bulk sample of 2 tons of ore has been sent away for treatment, but no return is yet available. For a distance of about 30 feet south of the foregoing excavation, shallow trenches have been sunk which prove the presence of tinstone. Continuing south for a distance of 81 chains into Mr. H. V. Crosby's claim, traces of 6 tin have been found, and a sample obtained from the trench in the latter claim was assayed with the following result:—Metallic tin, less than OlO per cent. In addition to the cassiterite, the following minerals were noted in the granite and quartz veins :—Chlorite, actinolite, crystals of tourmaline and quartz, limonite, hematite, arsenical stainings, native bismuth in minute specks, and a yellow powder, probably carbonate of bismuth. Mode of Occurrence .—Owing to the small amount of prospecting work carried out it is somewhat difficult to form an accurate idea as to the mode of occurrence of the tin deposits. The fact that prospects of tin have been found along a narrow belt striking north and south for 9 chains has led to the assumption that the tin is contained in a true fissure vein. The evidence available does not support this idea, however, for tin has not yet been proved throughout the entire length, but in a series of apparently disconnected patches, and no true channel has been proved. The cassiterite occurs in the granite and in a series of quartz veins and patches, and is indiscriminately distributed along certain belts of granite. In my opinion the occurrences are more in the nature of a series of disconnected pipes, the size of which have yet to be determined. Twenty-four miles north-east of Ardlethan, at Buddigower, similar occur¬ rences were worked some years ago, but are now abandoned. At Mulyan, 44 miles north-north-west, I reported on a tin field (Annual Report, Department of Mines, 1907, p. 173) of the same nature, but very little tin was obtained there. Prospects .—In view of the similarity between the Ardlethan deposits and those worked at the above localities, which proved to be of very limited extent, the outlook for permanency in the Ardlethan deposits is, in my opinion, not too promising. The presence of a permanent cheap water supply is essential for the economic treatment of a low-grade tin proposition, which must of necessity be of large extent. In view of the patchy nature of the tin contents in this granite, and the finely-divided state of the cassiterite, it will prove a difficult matter to economically win tin concentrates in this badly-watered area. It is doubtful if the first requirement could be obtained, whilst it has yet to be proved that an extensive tin-bearing area, even of low grade ore, occurs in this neighbourhood. As regards working the deposits, I would advise the prospectors to paddock out the tin-bearing areas, and handpick the ore sufficiently to produce a marketable standard.’’ At this stage it must be remembered that only a few shallow trenches had been excavated, and that the type of ore found on this tin field is not common. Even at the present time kernels of ironstone, absolutely devoid of any tin contents, are being unearthed in association with similar nodules, partly ironstone, but containing from 2 to 20 per cent, of tin. A further factor in connection with the writer’s first report, and the mines subsequently worked, is that the trenches then opened up remain to this day with no further work done upon them, whilst the present mine workings had not been touched at that stage. T At a later period in the same year, Mr. E. F. Pittman, A.R.S.M., at that time Government Geologist, visited the field, and furnished the following report* :— Report on the Ardlethan Tin Lodes. (E. F. Pittman). “ Although large quantities of tin have been found in New South Wales (over £9,000,000 worth has been won in the State up to the present time), the occurrence of tin-bearing lodes of a permanent character is comparatively rare, and for this reason the accounts which have found their way into the newspapers of the recently discovered stanniferous lodes at Ardlethan have excited a considerable amount of interest amongst mining men. These lodes are situated in the parish of Warri, country of Bourke, about 3J miles to the north-w’est of Ardlethan, which is a small town situated 337 miles from Sydney on the railway line from Temora to Barellan. About eleven or twelve years ago tin was discovered at Buddigower, 12 miles south-west of Wyalong, and about 20 miles north of the present find. The Buddigower lode was described by me in the Annual Report of the Department of Mines for 1891, page 158. Some good ore was obtained from these mines, that occurring on the surface being particularly rich, but the deposits did not prove to be permanently payable, and active operations were abandoned about six years later. The town of Ardlethan is situated upon a belt of thin-bedded slates and sandstones of Silurian (?) age. These sediments dip to the west and south-west, and about a quarter of a mile to the east of the railway station they are overlain unconformably by thick-bedded coarse Devonian (?) sandstones which have a north-westerly strike, and which dip to the north-east at an angle of about 50 degrees. About a mile or two to the westward of the township of Ardlethan, the Silurian slates give place to granite, and it is in the granite, close to its junction with the slates, that the tin-bearing lodes occur. It may be remarked in passing that in this respect the mode of occurrence of the Ardlethan lodes is similar to that of the Buddigower lodes previously referred to. The Silurian slates are clearly the oldest rocks of the district, for the granite has intruded them, and near their junction the slates have been converted into micaceous schists by contact metamorphism. In view of the fact that this is a populous district, it is very remarkable that the Ardlethan tin lodes should have remained undiscovered for so many years, for in some cases large masses of very heavy ore, consisting of cassiterite or tinstone encrusted with a considerable proportion of iron- oxide, have been found on the surface. Occasionally these masses have been found as much as 1 ton in weight, and have yielded from 40 to over 50 per cent, of metallic tin. The lodes are situated in alienated land, and, consequently, it has been necessary for the miners to apply in the first instance to the Warden for authorities to enter and prospect, in virtue of which they can subsequently obtain leases from the Crown. • Annual Report, Department of Mines, Sydney, 1912, pp. 173, 174. 8 The prospector’s claim, or the first in which tin-ore was proved to occur, is now known as the “ White Crystal ” (portion P.M.L. 3, Keogh and party). The only work done on this claim at the time of my visit consisted of two trenches, and a shaft about 30 feet deep. In the latter the lode had a width of about 4 feet, dipping to the west at an angle of about 70 degrees. Some good ore was showing in the shaft, the cassiterite being distributed in grains through a gangue consisting of quartz with some felspar, and I was informed that 22 tons of ore had been sent away, but its value had not been ascertained, as the returns had not been received. Adjoining the White Crystal is the Carpathia Tin Mining Company’s land, surveyed as portion P.M.L. 4, of 16 acres. On the surface of this claim ■ there was a large accumulation, about 20 feet wide, of ferruginous tin stone in boulders and masses ranging up to several feet in diameter, and con¬ taining from 40 to 55 per cent, of tin. The occurrence of this rich deposit of ore appears to have led some people to assume that it was the outcrop of a solid lode of tinstone 20 feet in width. In reality, however, it represented the accumulated ore resulting from the denudation, during past ages, of the upper poraons of the lode. The gangue, after having been decomposed by atmospheric influences, had been washed away, while the tinstone, being heavy and comparatively indestructible, had remained where it had fallen, and formed a concentrated deposit of rich ore covering the lode. The first parcel of 10 tons of this ore despatched from the mine is said to have contained 40 per cent, of tin, and 34J tons realised, I am informed, over £2,500. After clearing away the loose surface ore, the lode immediately below it was found to be 12 feet wide. An excavation of 12 feet by 6 feet in horizontal dimensions had reached a depth of 12 feet at the time of my visit. It showed that at a depth of from 6 to 8 feet below the surface the lode was in three sections, viz. :— (1)3 feet of fairly solid ore on the eastern or foot wall; (2) 2 ft. 6 in. of similar ore on the western or hanging wall, and between these there was (3) a mass 6 ft. 6 in. in width of decomposed gangue with occasional pieces of tin stone scattered through it. Representative samples of these three widths of ore were carefully taken, and were assayed in the laboratory of the Department of Mines. The results showed that the eastern 3 feet averaged 16-63 per cent, of tin; the western 2 ft. 6 in. averaged 17-02 per cent.; and the central 6 ft. 6 in. averaged 9-33 per cent. The average contents of the total width (12 feet) of the lode at this spot, therefore, works out at 12-75 per cent, of tin. This is, of course, an excellent result for such a width, considering the present extremely high price of tin, and if the lode be found to maintain anything like this width and value at a depth, there should be no difficulty in working it at a profit. In the meantime, however, it can only be said that the amount of development work done is so insignificant that it is impossible to express a definite opinion as to its future prospects. There were two other trenches across the lode in this claim, viz., one situated about 36 feet north of the last-mentioned excavation, and the other about 20 feet to the south of it, but the greatest depth attained in either of these was only about 4 feet, and tliev therefore afforded very little indication of how the lode may be expected to develop at a depth. Near the southern boundary of the claim, the outcrop of the lode, showing good ore, was visible, but its dimensions had not been proved, though apparently considerably less than in the excavation previously referred to. The course of the lode in this claim appears to be about north 26 deg. east, and it dips west 26 deg. north, at an angle of 48 degrees. 9 To the south of the Carpathia mine is Baker and party’s claim (surveyed as portion P.M.L. 1), and known as the “ Champion.” The same lode that occurs in the Carpathia has been traced through this block, though here its course has changed more to the south-west. A trench has been cur along the course of the lode for about 50 yards in length, and from 2 to 5 feet deep, and from this, and from a small shaft, which at the time of my visit had reached a depth of 10 feet, about 16 tons of good ore had been extracted and bagged, though none of it had been sent away. In the 10 feet shatt, which was in hard granite, the lode appeared to be about 5 feet wide, while in the trenches it was not more than half that width on the average. The Homeward Bound Mine, Clifford and party, surveyed as P.M.L. 2, is situated about a quarter of a mile to the west of the Carpathia, and it possesses the distinction of having the deepest shaft on the field, though this is only 40 feet. The lode in this mine has a strike of north 24 deg. east, and is nearly vertical. A shaft 8 feet deep, near the eastern end of.the claim, shows the lode less than 1 foot in width, while in the main, or 40-feet shaft it was only 4 inches wide when first met with, but has widened out at the bottom, where it varies from 2 to 3 feet, and in the centre of the shaft bottom there is a “ horse ” or barren portion. I was informed that the following parcels of ore had been sent away from this mine :— 17 tons 17 cwt. of picked ore yielded 18 per cent, of tin. 5 tons of picked ore yielded 10—11 per cent, of tin. There are 20 tons of “ firsts ” still at grass, and also 40 tons of “ seconds ” estimated by the owners to contain 7 per cent, of tin. Wallis’s claim (portion P.M.L. 6) is east of and adjoining the Homeward Bound. The lode at the surface is from 9 to 15 inches in width. Its course is north 20 deg. east, and it is nearly vertical. The amount of work done is insignificant—three potholes—the deepest 6 feet, having been sunk, and no ore has as yet been sent away. Another lode to the west of this, and . approximately parallel with it, is owned by the same party. It is about the same width, and the deepest excavation upon it is about 4 feet. Wallis and party have also another claim (portion P.M.L. 5) to the west of the Homeward Bound. A shaft 21 feet deep shows the lode to have the same bearings as in the Homeward Bound. Its width here varies from 2 to 3 feet, and it is nearly perpendicular. There were, at the time of my visit, about 10 or 15 tons of ore at grass, but none has been sent away, and con¬ sequently its value has not been ascertained. The Wild Cherry claim (portion P.M.L. 9) is situated to the south-east of and adjoining the Homeward Bound Mine. A trench 12 feet deep and 30 feet long has been constructed along the course of the lode, which bears north and south, and dips to the east at an angle of 44 degrees. The lode is seen to vary in width, within the limits of this trench, from 6 inches to 3 feet 3 inches. A parcel of 20 tons of ore was sent away, and yielded 24 tons of concentrates containing 61 per cent, of tin. This works out at about 7*6 per cent, of tin in the ore. There are about 7 or 8 tons of similar ore in bags at the mine. There is quite a number of other claims in the vicinity; but in no case has sufficient work been done to justify a definite opinion as to the prospects of these lodes at a depth. It is clear, however, that the lodes are lenticular in form; in other words, they will be found to vary in width from an inch or two to several feet (or in exceptional cases even more), and the variation 10 in width will occur in a vertical as well in a horizontal direction. Moreover, there can be very little doubt that the tin-ore will be found to occur in chutes , as is the case in all other tin-bearing lodes, and that the productive chutes will be separated by more or less barren or unproductive portions. The country rock must also be expected to become harder as depth is attained, with a corresponding increase in the cost of mining, and, further¬ more, it must not be forgotten that tin is at present at a phenomenally high price, at which it cannot be expected to remain permanently. It seems necessary to make these remarks in the public interest, because there seems to be a somewhat unjustifiable excitement on the Ardlethan Field at the present time. The claim-holders there have a tendency to “ talk in thousands,” and as a matter of fact claims have changed hands for very large sums of money, although I must confess that the amount of work performed upon them was totally inadequate to enable me to form a reliable estimate of their value. The most that one is justified in saying at the present time is that the surface indications are favourable for the occurrence of payable chutes of ore in some of these lodes, but a very considerable amount of work will require to be done before it can be confidently stated that any of them will be permanently payable. Small quantities of bismuth and wolfram have been found associated with the tin. There is a decided similaritv in the mode of occurrence of these tin-bearing lodes of Ardlethan and the auriferous lodes of Wyalong; both occur in granite close to its junction with Silurian slates, and both are distinctly lenticular in shape. It will be interesting to see whether the analogy is further borne out in the matter of the depth to which payable ore extends. Judging by the amount of ferric oxide present in the tin ore found at the surface, it is probable that below the water-level the tin will be found‘associated with much arsenical pyrites, as is so frequently the case with lodes of this character. The Bygoo Lodes .—Another group of tin-bearing lodes has recently been found in granite rocks at a locality known as Bygoo, situated about 6 or 7 miles in a north-west direction from the town of Ardlethan. In their mode of occurrence the Bvsroo lodes differ somewhat from those of Ardlethan. They are of considerable size, 10 to 20 feet in width, and have bold outcrops of quartz, in which the tin is disseminated in small grains, and in which it is also associated with a little wolfram and much tourmaline. The lodes appear to be more or less parallel to one another, the prevailing strike being about E. 20 deg. X. There has been very little work done upon these lodes, the deepest pothole being about 6 feet deep, and although 5 tons of picked ore have been sent away, no return has yet been received. It is evident that a considerable amount of concentrating will be necessary with the ore from these lodes, as the cassiterite which occurs as small crystals is more or less sparsely scattered through hard white quartz.” During 1915, Mr. J. R. Godfrey, Inspector of Mines, thoroughly inves¬ tigated the various mines and prospecting shows. His report* deals essentially with the mode of occurrence of the ore bodies, and their actual assay value at the time of sampling same, with an expression of opinion as to the probable tonnage and value of the ore more or less actually in sight. Since that report was published, the tonnage and values has been greatly exceeded in many cases, but this is largely due to further development work • Mineral Resources, No. 20, Geological Survey, New South Wal s Sydney, 1915. 11 having exposed ore bodies, the value and tonnage of which could not be considered in a Mining Engineer’s report dealing with present and not potential makes of pay ore. This report should prove of considerable interest to the student of ore bodies and be of great value to future prospectors and mining companies on this field. It will be noticed on perusing the reports by Mr. Pittman and the present writer, that whilst the latter considered the sedimentary rocks in the neighbourhood of Ardlethan to be referable entirely to the Devonian period, Mr. Pittman expressed the opinion that both Devonian and Silurian sediments were represented. No fresh concrete evidence was obtained during the recent geological survey, so that the geological age of either beds •still remains in doubt. The question is discussed in another part of this report, but the specific geological age of these beds has no importance with regard to the tin occurrences, and so may remain a matter of opinion until palaeontological evidence is forthcoming. HISTORY OF THE FIELD. Mr. George James, Mining Warden, who in his administrative capacity has been intimately associated with the field since its opening, has supplied the following historical record. The first application in connection with the Ardlethan Tin Field was made by Mr. J. J. Keogh, in May, 1912, and at the Warden’s Court, on the 24th of May of that year, authorities to enter covering, among others, the Carpathia and White Crystal Mines were granted. The mines, excepting those at Little Bygoo, are entirely on “ private land ” in the parishes of Warri and Ramsay, and county of Bourke, and the land on w^hich tin was discovered, viz., part of portion 40, parish of Warri (now the Carpathia), was part of Warri Station. Reports are common that numbers of people had from time to time remarked on the extreme weight of loose stones and boulders at this spot, and the owner of Warri Station, Mr. Wellman, claims to have known that t'n ore existed; but if so he seems to have considered it not worth while bothering about, while no one else seems to have known of its identity or value. Mr. J. J. Keogh was, therefore, the first to send some of the ore contained in the loose boulders for assay, and followed it up by taking up and prospecting the ground, thereby becoming the discoverer and pioneer of the field. The outcropping boulders and stones on the Carpathia lease, on being bagged and sent to a Sydney buyer, proved to be extremely rich, so that the syndicate of six, of which Mr. Keogh was the principal, speedily had a dividend of some hundreds apiece, but some doubt was felt lest this ore should prove to be an isolated patch remaining from a denuded zone, and for some months it could not be realised that bodies of rich tin ore were awaiting development. The ground was gradually prospected, however, and the ore where the Carpathia shaft now is was exposed. At this time it engaged the attention of Mr. W. W. Young, then on a visit of inspection to the “ Mallee Hen,"’ a gold mine in the district, and presently the lease was sold for £7,000 cash and something like 10,000 paid-up shares in a company being formed to acquire and develop the property. 12 The area of the lease, P.M.L. 4, was about 15 acres. This sale was ollowed by that of the White Crystal leases, some five in number, having an area of about 70 acres, the principal being P.M.L. 4, held by Mr. Keogh, for £26,000 cash and a number of paid-up shares. Shortly followed a “ boom ” period when shares, paid up to a few shillings only, rose to nearly thirty shillings each, and during which several other companies were formed to acquire and develop other leases. These will be mentioned in turn. For some reason or other, and without the value of the mines or the shares being either proved or disproved, the investing public became alarmed and lost confidence, and share market values depreciated to such an extent that many speculators who bought in a high market lost heavily. This had the effect of causing the field and the mines to be looked on generally with disfavour for some years after, and although the progress made was generally good, and sound work was done giving a valuable output each year, it was long before even a section of the public realised that the Ardlethan field held promise of sound mining propositions and was worthy of attention. The value of the output, collectively and of the various mines, as published each year in the Annual Report and mentioned later on shows that those immediately connected did their best, and much credit is due to the indi¬ vidual lessees who prospected and developed a considerable number of leases. During 1913 a tremendous activity in the taking up of authorities to enter and leases was manifested, and at each fortnightly Warden’s Court for some months an average of eighty or ninety applications were dealt with. The Department detailed a special Warden's Clerk, with two Warden's Bailiffs to meet public requirements, and up to the present time nearly 2.000 applications for authority to enter have been made. A number of Crown Lands leases, principally on stock routes and reserves at Bygoo, have also been taken up, and a total of nearly 600 lease applications have been made, the majority of which have been granted. The principal mining companies formed were as follows :—The Carpathia and White Crystal, already mentioned, the Wild Cherry, the Southern Cross, Big Bygoo, and Drumlish Hill. The Ardlethan Options also acquired rights over a number of leases, and various svndicates or individuals held and worked leases, such as the Homeward Bound, Champion, Wallace Brothers, Outcast. Outcast Extended, Central Options, Commonwealth, Perseverance, Black and White, Kiora, Vulcan, Killarney, Lone Hand, Dumbrell's Bvgoo, Corner’s Bygoo, Sholtz's Bygoo, and others. The Wild Cherry is now known as the New Venture, while the Southern Cross, Drumlish Hill, and Ardlethan Options are either defunct or are not prominent at present. But in every case except that of the Southern Cross, the leases are being worked by later holders with considerable success, and developments appear to justify the hopes entertained when the companies were formed. The following details relating to some of the various mines may now be recorded :— The Carpathia has so far been the leading producer, and at the end of 1918 the output amounted in value to over £150.000, the sum of £40.000 having been distributed in dividends; this amounted to a great deal more than the capital laised to purchase and equip the mine. The New Venture (formerly the Wild Cherry) has contributed tin to the value of £23,000 odd, and has pioneered in the matter of boring for water, • a good supply having been found at a depth of something over 200 feet. 13 The White Crystal’s output has realised a total of £35,906 during the year, and favourable developments have occurred which may greatly increase the supply of concentrates. The Southern Cross erected a 10-head battery and plant, but failed to find tin in payable quantities on its leases. The plant has, however, been of incalculable value in the development of the field, as it has regularly treated ore for the public for some years past, and has thus proved the value of numbers of holdings. It has been a tremendous boon to numbers of lease holders and prospectors. The Homeward Bound, and also Wallis mine, lying west of the New Venture, were highly payable in the early days, and are both promising mines at the present time. The Bygoo end of the field, though retarded by want of water, distance from battery, and the fact that the majority of the mines were retained and worked by the original finders, is now being developed, and promises favourable developments. Foremost is Big Bygoo, which languished for some five years, but during the last two years has produced concentrates to the value of nearly £20,000. A plant is now being erected on the mine, and the outlook is particularly encouraging. Dumbrell’s Bygoo has produced 1,000 tons, averaging 5 per cent., some of the ore being over 60 per cent. Corner’s Bygoo and Scholz’s Block 5 have also produced consistently in the past, but at the present further development work is needed to prove their permanency. The total production of the field to the end of 1918 had a value of about £343,000, and the output of some of the individual mines was— Tons. £ Carpathia . . 17,435 156,965 White Crystal . . 8,000 35,906 New Venture . . 14,000 23,574 Homeward Bound. . 1,350 9,570 Wallis . . 600 6,695 Big Bygoo . Dumbrell’s Bygoo . . 2,500 18,644 . 1,000 6,350 ACKNOWLEDGMENTS. It is not necessary to specify individually those who rendered the writer «very possible assistance during the field examinations and preparation of this work. All were willing to render every facility for gleaning information, and assist in every way possible. Mr. Godfrey’s report on the field proved of great help, as also did infor¬ mation supplied by Mr. Warden James regarding past operations and yields. Mr. Ellis, manager of the Carpathia, was in a position to supply much useful information as to costs, and working or prospecting conditions, whilst special thanks are due to Mr. Terry, manager of the New Venture Mine, for pointing out the surface exposures of porphyry, and underground provings of the same rock. 14 CHAPTER 2. GENERAL GEOLOGY. The accompanying geological sketch plan indicates the relative positions of the three principal tin belts in the neighbourhood of Ardlethan, together with the associated geological formations. The latter may be divided into two groups, namely, sedimentary and igneous, but there is a considerable area of each which is entirely covered with a waste sheet of soil, so that it is only possible to determine the actual contact in a few places. In addition to the waste sheet above referred to, a considerable accumu¬ lation of shed material occupies a depression on the south-west side of Carpathia Hill. This deposit has been proved to be of considerable economic importance on account of its tin contents, and is referred to locally as the “ Alluvial Ground.” That it is not a true alluvial deposit is evidenced by the angular and sub- angular nature of the whole of the contained material, and it is best classed as an accumulation of detrital material. Sedimentary .—The sedimentary rocks consist mainly of quartzites, fine¬ grained micaceous sandstones, slates, and a coarse breccia formed of frag¬ ments of similar rocks, all more or less altered. Known exposures of the latter are not numerous, and are always found in juxtaposition to the granite, the most noticeable exposure being on the Carpathia Hill, where it forms quite an attractive rock type. East from Ardlethan itself, and extending for many miles north and south of that village, sandstones, in places pebbly, predominate, all dipping at from 20 to 60 degrees to the westward. Igneous. Granite .—At a period subsequent to the folding of the sedimentary rocks an extensive granitic intrusion forced its way into the belt of country lying some 3 miles west of the village of Ardlethan. This intrusion consists of alternating belts of coarse and fine grained granite or aplite, and can be traced many miles north from Ardlethan, whilst it was followed south as far as Bald Hill, some 8 miles to the south-west. The width ranges from 5 to 8 miles, but as a large part of the land surface is covered with a waste sheet, its actual boundaries are for the most part obscured. Porphyry .—At a still later stage, the granite was intruded along its eastern edge by a dense quartz-felspar,-porphyry. Five surface exposures of this rock were located in the vicinity of the Carpathia group of mines, and it has been exposed in several of the mine workings. Most of the surface exposures resemble dyke outcrops, that is, are relatively much longer than they are wide, but about 1 mile west from Carpathia Hill an outcrop occupying some six or seven acres is to be seen. 15 DETAILED GEOLOGY. Sedimentary .—As already pointed out, no palaeontological evidence as to the geological age of the sedimentary beds has yet been obtained, but, on lithological grounds, the writer strongly favours referring them all to the Devonian period. Some 10 or 12 miles south from Ardlethan, at Murril Creek, in the neighbourhood of the Mallee Hen Gold Mine, a belt of steeply dipping, highly fessile clay slates occurs. These beds differ entirely from the sedimentary rocks found adjacent to the Ardlethan tin belt, and are of a lithological type nearly always associated with beds of Silurian age. On the other hand, the sedimentary rocks near to Ardlethan have all the charac¬ teristics of proved Devonian beds in the State of New South Wales. The present writer’s opinion as to the age of the sedimentary rocks adjacent to the Ardlethan tin belt is arrived at in the light of the foregoing evidence, and it' is considered that any local variation in proximity to the granite in¬ trusion is due to contact metamorphism. These views, however, yet remain to be confirmed by palaeontological evidence, of which none was obtained during the recent examination. In the writer’s opinion prospecting in these beds is not likely to lead to important mineral finds, unless it be in proximity to the granite or porphyry contact. It may be, however, that apophyses of the latter intrusion will be found at no great depth beneath the surface along the western boundary of the sedimentary rocks, in which case mineral deposits (tin, wolfram, &c.) may occur, but these would undoubtedly be mainly confined to the porphyry. The breccia referred to has probably been partly formed at the close of the granite intrusion, bv more or less open spaces being left in places between the surface of the granite and the overlying sedimentary rocks, for wherever the contact could be observed, a sharp line of demarcation exists between the two. This would lead to a shelling off of the latter and aloose accumula¬ tion of angular fragments in the shrinkage cavities. The solutions accompanying the porphyry intrusion then deposited their mineral contents in the loosely packed fragments, thus forming a compact rock mass. The breccia in places is charged with tin oxide and copper car¬ bonates, and this, in the writer’s opinion, goes far to substantiate the theory that the mineral contents of the Ardlethan tin field are attributable to the porphyry intrusion. In the large open cut within the Champion leases, an excellent exposure of breccia is to be seen. The cut started in granite the intrusive nature of which is well seen here, but soon passed through it into the brecciated sedimentary rocks. A pronounced fault is seen close to the contact, striking north 30 deg. east, and dipping north 60 deg. west at an angle of 42 degrees, but the amount of displacement could not be determined. A prominent outcrop of porphyry is to be seen adjacent to the open cut, and the writer attributes the fault to the intrusion of that rock, for similar fault planes were identified in the granite itself, thus proving that faulting took place subsequent to the intrusion of that rock. Granite. Intrusive .—The geological age of this intrusion is apparently post-Devonian, for it is seen intruding rocks to which that age has been assigned, and it appears reasonable to assume that it took place during the Carboniferous period in common with many other granite masses in New South Wales. 16 There has been considerable magmatic differentiation, and several distinct types were observed. These occur in belts from a few feet up to many yards in width, with a more or less meridional strike. As the mass is crossed from east to west, the most noticeable features are that the eastern periphery consists largely of a highly acid type over much of the exposed area, that is, the comparative absence of felspar is very marked, and mica is only sparsely dessiminated through the rock, or occurs in isolated bunches. Secondary silieiiication has undoubtedly played a large part in the present composition of this granite type, apart from its original composition. The writer is of the opinion that the porphyry intrusion was accompanied by highly-charged mineral solutions, which impregnated the rock mass within their scope of influence, and also replaced portion of the original constituents. In other words, they not only dissolved out most of the felspar constituents, but replaced them by amorphous silica, metalliferous deposits, and, in some cases, by topazisation and other alteration products. Continuing west, the granite is found to become more holocrystalline,and to contain a comparatively high percentage of felspar, with an equivalent increase in the ferro-magnesian constituents. These belts alternate with either semi-acid or a fine-grained variety of rock. In the latter, a marked association of tourmaline is present. All the available evidence points to the more acid type of granite being most favourable for the occurrence of payable deposits of tin ore, and this should be a sound guide to prospectors. Porphyry .—That there has been an intrusion of porphyry subsequent to the granitic intrusion is evidenced both on the surface and underground in mine workings. Five surface exposures were located, as shown on the accompanying geological sketch map, and a number of occurrences are to be seen in the underground workings. These are best seen in the ** alluvial ground of the New Venture mine, but other occurrences noted were in a shaft on a lease held by the Ardlethan Options, at present being worked on tribute by Mathieson and party (P.M.L. 157, parish Warri). One or two exposures were examined in the Carpathia mine workings, which probablv represent the porphyry, but here advanced alteration renders a definite identification impossible, even under the microscope. In other cases certain highly altered rocks have been classed as porphyry by mining men on the field, but it appears probable that these represent phases of the original granite intrusion, probably in close proximity to the later intrusion, and consequently much altered. The surface exposures of porphyry have all the appearance of comparatively narrow dvkes, or might even be attributed to magmatic differentiation, but underground work proves that a large mass of porphyry underlies the granite in this neighbourhood, and has intruded it. In other words, the surface exposures represent narrow apophyses of porphyry extending upwards beyond the main mass. 17 The bulk of the exposures disclose a typical quartz porphyry, the porphyritic crystals consisting of glassy quartz, which are embedded in a light-grey base, probably more silicious than felspathic. In places the outcrops disclose a much pitted rock, due to the quartz crystals becoming detached from the surrounding base. The exposure in the south-west corner of portion 19, parish Ramsay, about half a mile north-west of the Ardlethan Mines Public School, consists of a dark-blue felspar porphyry, with an almost entire absence of visible quartz, but the writer considers this to represent a portion of the porphyry intrusion in which the felspar has developed at the expense of the quartz. The relative age of the porphyry intrusion is incapable of proof, but the writer inclines to the opinion that it took place at no great period after the granite intrusion, and represents renewed activity in the original magma basin. Mr. E. C. Andrews, B.A., Geological Surveyor, in dealing with the ore deposits associated with the New England granites(*) points out that “ into the late Palaeozoic strata a number of granitic rocks were thrust, the earlier ones being basic varieties, the younger members being of much more acid types.” This, in the writer’s opinion, premises the genealogical conditions which pertained on the Ardlethan tin field, and a post-Devonian age must be assigned to both the granite and the porphyry, with the latter intrusion post¬ dating the former. Although the presence of porphyry was only observed in the positions men¬ tioned, the writer holds the view that the secondary silicification of the granite, with accompanying metallic mineral deposition found along the eastern periphery of the granite at the Bald Hill, Carpathia, and Bygoo groups of mines, is due to that intrusion. The reason for this assumption is based on evidence that is more or less intangible, but may be summarised as follows :— 1. The tin deposits have already been traced down into the porphyry in several instances, thus establishing a genetic connection. 2. The ore bodies are almost entirely associated with an altered acid type of granite. This alteration is most marked in the neighbour¬ hood of the porphyry outcrops, or along the belt of country likely to be affected by that intrusion, i.e., the junction between the granite and sedimentary rocks. 3. If the origin assigned to the breccia be correct, it naturally attributes its silicification and mineralisation to a later period than the granite intrusion. True, there are no direct evidences of the porphyry at either the Bald Hill or Bygoo ends of the field, but the geological horizon, i.e., the contact line between granite and sedimentary rocks is the same in each case, and the alteration products are identical. * “ The Geology of the New England Plateau, with special reference to the Granites of North New England,” Geological Survey Records, Vol. VIII, part 2, p. 110. 18 CHAPTER 3. THE NATURE AND PROBABLE GENESIS OF THE ORE BODIES. The ore bodies on this field may be divided broadly into two classes, namely :— A. Deposits in situ ; and B. Deposits of shed tin, referred to locally as the “ alluvial ground.” Class A. consists of : 1. “ Bungs,” pipes, and irregular-shaped bunches or lenses. These are found lving at all angles to the horizon, and are apparently indiscriminately disseminated through the belt of country affected by the porphyry intrusion. The ore bodies vary in size from small isolated kernels to pipes over 40 feet long, 30 feet wide, and a vertical height of upwards of 100 feet, with average tin values up to over 20 per cent. tin. 2. Impregnated zones containing finely disseminated cassiterite, which merge imperceptibly into the surrounding country, and are common along fault planes. 3. Face tin, consisting of crystalline cassiterite deposited upon joint faces of the altered granite, which in itself carries practically no tin. 4. Veins of tin-bearing material (mainly silica), deposited actually in fault planes and along parallel zones of stress, whereby permeation by the tin-bearing solutions was facilitated. Class B.—Deposits of shed tin, or the so-called “ alluvial ground,” have so far only been found along the drainage system lying between the main Carpathia group of mines, and a range of hills upon which the Southern Cross battery is situated, the locality being indicated on the accompanying geolo¬ gical map. Many thousand pounds worth of tin have been recovered from this ground, the nature of which is somewhat unique in the writer’s experience. The following sketch transverse section illustrates the nature of the deposit:— fast West 13 rid _ Str&ce n aL - - " ~ ' • nr'?'' "Southern Cross Hill Sketch section of Alluvial Ground (Showing associated formations) Alluvial Ground shown thus Sedimentary »» •• «o ^ * * ^ . <7 y - --- - Granite shown thus Porphyry » •• \'^-n / ^1 v 1 Alluvial Ground ” from New Venture Mine. 19 With regard to the genesis of tin deposits in general, the reader is advised to refer to “ The Tin Mining Industry, and the Distribution of Tin Ores in New South Wales.”* In that publication Mr. J. E. Carne, F.G.S., Government Geologist, gives a concise epitome of the view r s held by the world’s leading authorities regarding the genesis of tin deposits. The following are the opinions held by the present writer regarding the. genesis of the Ardlethan tin deposits :— As already stated, the mineral deposits of this field are, in the writers’ opinion, intimately associated with the porphyry intrusion, for not only do we find the ore bodies extending down into that rock, but in every instance they are associated with the alteration and replacement products which were undoubtedly the result of that intrusion. It is considered that the vapours and solutions accompanying the porphyry intrusion were heavily charged with mineral contents, which were deposited within the cooling zone, both of the porphyry itself, and the overlying rocks.. The importance of this, in the writer’s opinion, cannot be over-estimated, for not only does it offer a guide in carrying out prospecting work, but also points to a far greater degree of permanency for the ore bodies than might have otherwise been attributed. For instance, the proving by the manager of the New Venture mine, that high tin values extend down into the porphyry for at least 50 feet, shows that conditions for the precipitation of tin ore were favourable in the parent or genetic rock. Other conditions being equal, such as precipitating agents in the presence of solutions capable of in part replacing the original rock, it is what might be expected, for the cooling zone in a large intrusive mass coming from unknown depths, would not be confined to rocks immediately surrounding it, but also extend downwards into that rock itself, possibly to a considerable depth. Eight here it might be advisable to point out that not only would the tin contents of the solutions by which it was introduced be more or less limited, but also that favourable conditions for tin precipitation did not exist over the whole zone referred to. Hence extensive blanks are inevitable, and the miner must expect to have to carry out considerable dead work between makes of pay ore. Origin of the Deposits of Shed Tin. There is no doubt that bodies of running water did not cause this accumu¬ lation, for the recorded annual rainfall of this district (19 inches per annum) precludes the possibility of any large accumulation of truly water-borne material during recent times, and there is no evidence in this district of an accumulation of water-borne material during the Tertiary period. The Ardlethan “ alluvial ” occurrences are, in the writer’s opinion, due entirely to accumulations of shed material, derived from a more or less vertical escarpment or cliff line. In other words, that during Post-Tertiary * Mineral Resources, No. 14, Geological Survey of New South Wales, by J. E. Carne, F.G.S., Assistant Government Geologist, Sydney, 1911, pp. 20-26. 20 and geologically recent times, there existed a steep declivity to the west of Oarpathia Hill, and also in places on the Southern Cross hillside. The waste material from this escarpment was shed into a drainage channel with a gentle southerly fall, as evidenced by present-day mine workings. There was apparently not sufficient flow of water to remove the material, hence its accumulation practically where it had fallen. At the top or northern end, the detrital material consists almost entirely of decomposing granite fragments embedded in a red clay, with occasional fragments of sedimentary rock, porphyry, and tinstone, whilst much of the clay itself carries tin values. The rock fragments range in size from an inch or two to several feet in diameter, and are so bound together by the clay matrix, that practically no timbering is required in the workings. The above material rests on an uneven floor of either granite or porphyry, the former being more or less decomposed, but the latter only showing slight signs of weathering. As the 44 lead ” is followed down, the detrital material consists essentially of fragments of sedimentary rock, all of smaller dimensions than the granite detritus, embedded in clay, and resting on a floor of decomposed slate. With the above are associated a fair percentage of angular and subangular frag¬ ments of cassiterite, more or less in layers. The depth of sinking ranges from 25 feet at the southern end up to 86 feet at the northern end (New Venture workings), or head of the 44 lead." This appears somewhat anomalous, but is explained by the fact that the present land surface falls more rapidly than the ancient one. The payable tin contents in the lower portion of the 44 lead ” is confined to two or three horizons, the top layer being about 15 feet from the surface, No. 2 about 25 feet, and the other just above the bed rock. At the northern end the values are found to be more or less indiscriminately distributed throughout the entire occurrence. 44 Spuds,” or nodules, rich in tin contents, have been unearthed up to 301b. in weight, but the bulk of the tin contents ranges in coarseness from the consistency of granular sugar to that of walnuts. The whole of the material from the New Venture leases is sent direct to the battery, and averages just over 1 per cent, tin, whilst lower down (Winter's leases) the layers of payable tin-bearing material, ranging in thickness from a few inches to over a foot, is passed through wire-netting screens, up to one and a quarter inches in diameter, the screenings being sluiced in ordinary riffle boxes, Whilst the coarser material is hand-picked, and the best of it sent to a battery for treatment. The sluiced concentrates average about 69 per cent, of metallic tin, and returns from the battery show a recovery of from 5 to 10 per cent. From the lower portion of the lead, the yield ranges up to three hundred¬ weight of tin oxide per load (22 cub. ft. of dirt), but it is not found profitable to handle the material if the tin contents is below from 15 to 25 lb. per load, depending upon the price of tin and working conditions. 21 SUGGESTIONS AS TO PROSPECTING. An effort is made in this portion of the paper to use terms, or to so qualify them, that they may be readily understood by the ordinary prospector, to whom the following suggestions may prove useful. If the deductions arrived at as to the origin of the tin deposits on this field be correct, and there appears good grounds for accepting them, not only from the evidence obtained on the Ardlethan field, but from the generally accepted nature of tin deposits all over the world, the following suggestions should apply. The most favourable belt of country to prospect is, in the writer’s opinion, along the eastern edge of the granite mass, and within this belt attention should be devoted to makes of an acid type of granite, that is, one in which silica (quartz) predominates, or to zones in which the granite contains a preponderance of mica over felspar. Particular attention should be devoted to locating occurrences of quartz porphyry, that is a more or less compact rock containing separated grains of glassy quartz. Even if the porphvritic (readily distinguishable as com¬ pared with the ground mass) grains be felspar, favourable developments may take place. In underground work the same factors apply, and whilst it is not possible to definitely indicate the position of makes of pay ore, pronounced joints, or makes of “ channel material,” veins of ironstone, &c., might be followed with advantage. The miner is advised to become acquainted with the porphyry referred to, and once it is proved in mine workings, to keep in touch with it. Ur' t llUKO'S 1 IB’ " I may y ^ 1^20 22 CHAPTER 4. PAST AND PRESENT MINING, TREATMENT PLANTS, NATURES OF, ORE, RETURNS. There is no doubt that the nature of the tin occurrences within this area were not fully realized in the early days of the field, and the original identi¬ fication of the tinstone was arrived at from shed material, so that an expression of opinion upon the evidence then available was difficult. The prospecting results were so encouraging, however, that enthusiasts like Mr. J. J. Keogh and others persevered, and eventually succeeded in introducing capital into mining ventures, which were practically unknown quantities, but with potentialities at that stage undemonstrated, There ensued a boom time, when fabulous prices were offered and paid for various properties, many of which never showed any justifiable induce¬ ments for their flotation. In the past some of the companies floated were fortunate enough to be able- to operate on rich bungs of tin ore, which yielded handsome returns right from the start, but in a short time these “ bungs ” were worked out, and it became necessary to undertake underground prospecting work in search of new makes of payable ore. In many cases there was no available capital to carry out the necessary dead work, and many claims were abandoned. The early returns of tin produced, as published in the Annual Reports of the Department of Mines, are as follows :— Year. Returns. From June, 1912 . 500 tons (379£ tons sold for £7,741). 1913 . £42,536. 1914 . £25,332. 1915 . £53,771. 1916 . £29,593. 1917 . £62,069. 1918 . £77,383. It is not possible at this period to give the returns from each individual mine or claim, but there is no doubt that the Carpathia Company has been the largest and most consistent tin producer, and whilst the production at the Bygoo end of the field has been good, very little tin has been recovered from either Bald Hill, at the southern end, or Taylor's Hill, to the west of the Carpathia group. Particulars of the various claims worked or prospected are published in the comprehensive report by Mr. J. R. Godfrey, already mentioned, and the reader should refer to that publication for details. During the present year, some eight or ten properties have been producing tin, but the bulk of the ore won has come from the following mines :— Carpathia, New Venture, White Crystal, the “ Alluvial ” Claims, and Big and Little Bygoo. There are at present (June, 1919) five.batteries engaged crushing ore in the Ardlethan field, namely :—The White Crystal, Carpathia, New Venture, Southern Cross, and Little Bygoo, whilst the Carpathia Company also have a battery at Barmedman. Carpathia Mine. 23 The following mines were actively engaged during the inspection of the field :— The Carpathia Mine. The Carpathia leases apparently embrace an area very much affected by the porphvry intrusion, for not only are surface exposures of that rock found on three sides and in the centre of the leases, but underground work has proved that there are probably occurrences of it at the 200-feet level. The main shaft has reached a depth of 200 feet, with a drive south .for 150 feet, from which there is a crosscut 120 feet to the west. From the same level a drive extends 200 feet to the north, thus connecting No. 1 and No. 4 shafts. From the foot of the shaft at this level, a crosscut has been driven 44 feet in a southerly direction, from the end of which a winze has been sunk to a depth of 102 feet below the shaft. During June of the present year the winze was passing through a very rich pipe of ore, the proved dimensions of which were 35 feet long, 26 feet wide, and 75 feet deep, the average tin yield being from 18 to 20 per cent., with patches yielding up to 60 per cent. ore. In what is known as No. 4 shaft, the country penetrated consists mainly of a coarse breccia, containing both tin and copper values, and from rock speci¬ mens collected at the 200-feet level there is every reason to believe that the porphyry is very adjacent if not actually cut. Somewhat similar conditions are to be seen at the south end of the 200-feet level, and as the presence of both the porphyry and breccia is considered a favourable indication, prospecting work in the neighbourhood of either is likely to prove makes of pay ore. The large chute of ore proved in the 44-feet winze was located by following a make of soft granite heavily charged with iron pyrites, manganese oxide, chlorite, &c., but for the most part practically devoid of tin values. The following particulars regarding the plant of this mine were kindly supplied by the secretary of the company:— At Barmedman we have 15 head of stamps, small reverberatory roasting furnace, Wilfley tables, Frue vanners, rotary tables, grinding pans and buddle; whilst at Ardlethan the battery consists of 10 head of, say, 800 lb. stamps. The screens used are 12 and 14 mesh. There are also a rock-breaker, May jig, 1 set of Spit-Kasten classifiers, 4 Wilfley tables, 3 Frue vanners, 1 Krupp ball mill, 1 Edwards Duplex roasting furnace, and 1 small reverbatorv roasting furnace. The mill has been erected this year and will, we hope, soon be completed. The following returns of the output from this mine were supplied by the same authority :—- Period eridiri nr 31 at .Till v. 1913 . Tons Ore raised. . 1,357 Tons Concentrates produced. 202 Value. a 21,765 32,129 13,675 18,014 16,702 31,827 26,530 - - 0 -- - -j 7 -— . Year ending 31st July, 1914 . 31 st .Tnlv 1915 . . 5,430 . 1 674 367 154 198 152 99 31st July, 1916 . 31st July, 1917 . . 2,998 . 3 410 31st July, 1918 . . 2,102 182 99 31st July, 1919 . 203 Ore sold— 31st July, 1913—62 tons ore realised 31st July, 1914—11 ,, ,, 31st July, 1917—18 3lst July, 1918—12 „ ,, £8,997 £160,642 £ 4,132 763 2,113 1.989 24 The accompanying longitudinal section of the mine workings was kindly supplied by the management, and affords valuable information as to the extent of ore bodies proved to date. The ore won is classified as follows *— •7 to 3 per cent, tin . “ Seconds.” 3 to 14 ,, . “ Millings.” 15 to 30 ,, . “ Special milling.” Anything over this, and some of the ore goes as high as 63 per cent, tin, is termed selected. The seconds and selected ore are treated on the ground, and the milling and special milling at the Barmedman battery. The concentrates are sold to Mr. T. H. Kelly, of Sydney, and the following information from account sales placed at my disposal by the manager affords interesting information as to the nature and value of the concentrates. In April, 1918, sixty-eigh + bags of ore, weighing 4 tons 19 cwt. 2 gr. 15 lb., showed an assay value per unit of 58/9, the toal value per ton being £176 5s. The impurities as determined by assay are as follow Material. Sulphur. Arsenic. Copper. Bismuth. Le&d.f Wolfram. Ore . 2-90 1*55 042 . 0-35 0-55 0-70 per cent. Concentrates . 2-75 1-45 0-38 0*50 1-20 100 „ Calcined concentrates 0-20 0-18 010 010 0-35 V The above may be considered a fair average of the percentage of impuri¬ ties present, but a casual examination of crude ore on the trucks would lead one to expect them to be much higher. The White Crystal Mine. No outcrops or exposures of true porphyry were found on this company's property, but it was located on the surface a chain or two beyond the most northerly corner of the leases held. There is strong evidence, however, that an extensive intrusion of that rock will be found at no great depth, for the granite over much of the area held, particularly on Crosby’s or the White Crystal Hill, show secondary silifieation and replacement to a majked extent, such, in the writer’s opinion, being due to the action of the vapours and solutions which accompanied the intrusion of porphyry. The proving of a pronounced fault plane along the 40-feet intermediate level (which is 308 feet long), striking north and south and dipping west at 60 degrees, may also be taken as evidence of the presence of ^ body of porphyry at no great depth. Admitting that surface conditions represent a zone affected by the porphyry intrusion, but further away vertically from the mass of that rock than is the case in the Carpathia and New Venture leases, then the deduction is obvious that by deeper sinking, larger and more concentrated ore bodies may be expected.. The main shaft on this property is down to a depth of 240 feet (vertical). An intermediate level has been driven south for 308 feet at the 40-feet level, but the main levels are only driven 100 feet and 156 feet, the former being known as No. 1 and the latter as No. 2. Section N°2Shatt No.tth* Sooth Situated 444 booth of N®1 Shaft Scale 1 to SO PHOTO-LITHOGRAPHED BY W. A. GULLICK, GOVT. PRINTER, M&W The White Crystal Mine. At the time of inspection, a shallow winze from No. 2.level was exposing a nice chute of pay ore, but insufficient work had been done to enable an estimate to be formed as to its probable dimensions. Portion of the ore at present being won from the shaft workings is somewhat dirty, and has to be roasted, as is the practice of other mines on the field. This is rendered necessary by the presence of iron and arsenical pyrites, bismuth, &c., and an analysis of a typical sample of roasted ore is as follows :— Sulphur. Arsenic. Lead. Bismuth. Copper. Wolfram. 0-5 03 0-2 0-1 trace 3-2 The occurrence of wolfram within the area held is more pronounced than in other parts of the field, and may prove somewhat of a disadvantage, for it is found that the bulk of the concentrates sold contain from 2 to 3 per cent, of wolfram. An attempt was made to work Crosby’s Hill by means of an open cut, the whole of the material won being treated, but values appear to have "been too low to pay. A tunnel was then driven into the hill for a distance of 75 feet, on the left-hand side of the open cut, following a make of pay ore. At 50 feet, crosscuts have been driven in an easterly and westerly direction, the faces now being about 40 feet apart. This work has proved the existence of an extensive make of ore, all of which it is expected will pay to treat. About halfway along the tunnel, a rise has been put up for 70 feet to the floor of an excavation near the crest of the hill, and the material won is all sent to the battery. No definite infor¬ mation as to the value of the ore now being raised from Crosby's Hill is available, but it is estimated to yield in the neighbourhood of 2 per cent, of tin. The total production of the White Crystal Tin Mining Company, as published in the Annual Reports of the Department of Mines, is as follows :— 1913. —235 tons of ore sold for £3,132 early in the year. Total ore raised, 750 tons. 1914. —200 tons of ore raised. 1915. —Production valued at £17,386. 1916. —32 tons of concentrates, valued at £2,560. 1917. —2,500 tons of ore raised, and concentrates produced to the value of £8,107. 1918. —Production valued at £2,971, whilst tributors recovered over £3,000 worth of tin. During the first six months of 1919, 2,452 tons of ore yielded 45 tons of concentrates, according to the manager. The plant installed at the White Crystal mine is both up-to-date and efficient, but more power is desirable, whilst the water supply is adequate for all requirements, namely, a tank capable of storing twenty million gallons; so that given a continuous supply of payable ore for treatment, the company should be in a position to justify the capital expended, although developments prior to the present geological survey do not appear to have been too encouraging. There is reason to expect more favourable develop¬ ments at a greater depth, however, should the writer’s views prove correct. 26 The plant consists of two suction gas engines of 50 and 30 h.p. respectively^ An electric generator is installed for the purpose of driving a pump at the main dam, also a complete lighting plant. The ore is first passed through a Jake's rock-breaker, and fed thence to 10 head of stampers, weighing 1,250 lb. each, discharging through a 10-mesh screen. After passing through a classifier, it is treated by three jigs, the coarser material being fed to a grinding pan and thence to two Wilfley concentrating tables, whilst the overflow passes into Callow tanks. After treatment on two Frue vanners, it passes through the roasting chamber, and the former treatment is again repeated. The New Venture Mine. A portion of the present New Venture Company’s leases were originally known as the Wild Cherry Mine, and whilst a few rich “ bungs ” of tin ore were worked in the early days of the field, the original company eventually got into difficulties, and the new company was formed. On field evidence, there is good reason to expect favourable results from the leases now held, for not only does the porphyry outcrop prominently, but underground workings have cut it in many places, and payable tin ore has been followed down for over 50 feet in that rock. Mr. Terry, manager for the company, has realised the importance of the porphyry intrusion, and much of his prospecting work has been carried out with a view to prove the occurrence of ore bodies actually in the porphyry, and the significance of its proximity with regard to the likely occurrence of payable deposits of ore. The present company has acquired additional areas of tin-bearing for¬ mations, particularly within the “ alluvial ” belt, the importance of which had not hitherto been realised, with the result that they now hold an exten¬ sive tin-bearing area which promises to yield satisfactory returns if handled as a large low-grade proposition. The main shaft on the lode tin deposits is down to a depth of 150 feet, and considerable driving, crosscutting, and sloping has been done, but at the time the writer w r as on the field very little ore was being recovered here, as work was confined mainly to prospecting and winning ore from an adjoining shaft known as Hough’s. This shaft is down to a depth of 100 feet, and yielded some very rich ore during the early days of the field. The present company are driving towards the porphyry, an outcrop of which is seen on the surface some two chains easterly from the shaft. The “ alluvial ground ” is at present worked by means of an inclined shaft, which leads to workings up to 86 feet below the surface, but there is no doubt that open cut methods must eventually be adopted if safe and economic working conditions are considered. According to the manager, from twelve to thirteen thousand tons of material have been treated from this ground for a return of from f to 1 per cent, of tin, which, whilst not yielding any profit to the investors, paved all expenses, and provided a sinking fvnd, wisely to be devoted to the erection of a more adequate and economical treatment plant. The New Venture Mine. 27 The following returns for the four half-years, 1917-18, were supplied by the manager :— , q - 7 f First Half-year \ Second Half-year I oi ft / First Half-year \ Second Half-year 'ons of Ore Treated. Concentrates. Average Yield from Concentrates. 1,238 21 per cent. 1-7 2,812 37 1-3 3,000 27 •9 3,183 27 •8 From the foregoing it will be seen that the bulk of the ore treated was low- grade, but by economical management, despite unfavourable working con¬ ditions, and a practically worn-out plant, all working costs were met, and a sinking fund provided for an up-to-date and extensive plant. Mr. Terry gives his working costs as follows :— Mining, &c. £1 Os. 5d. per ton. Crushing . 5s. 9d. ,, Two shifts were worked, and the crushing was done by the battery referred to. The plant consists of a rock-breaker and denny grinder, 10 head of 1,000 lb. stamps discharging through a 10-mesh screen, feeding to five Card concentrating tables (one used for slimes only). The plant is driven by a 10 h.p. Jackass boiler, whilst another 10-15 h.p. boiler is used for winding. The new treatment plant is now in course of erection, and should be com¬ pleted by the end of the year. Provision has been made for an adequate water supply, and in addition to two large dams, a bore was sunk to a depth of 460 feet, adjacent to the main shaft, from which 10,000 gallons of water are now being pumped in the two shifts worked per day, the water rising in the bore to the 360-feet level. Other “ Shows ”—Carpathia Group. In addition to the foregoing companies in the Carpathia group of mines, there are several smaller companies or syndicates occupied in prospecting leases held. None of these are at present producing tin ore to any extent, but in the case of those adjacent to the porphyry intrusions shown on the accompanying map, the writer is of the opinion that the possibilities of locating makes of pay ore are favourable. There is little doubt that several of these shows have possibilities, but unless they are worked as low-grade propositions, i.e ., economic bulk treatment, considerable dead work must be expected if rich “ bungs ” are to be located. None of these shows are equipped with a treatment plant, but a public battery, known as the Southern Cross, is situated within a mile of any of them, and here parcels of ore can be treated at what appears to be a reasonable cost. This plant is provided with a Blake rock-breaker, a 10-head stamper battery (1,000 lb. stamps) discharging through 8 and 10 mesh screens. 28 with four classifiers, two Wilfley and two Card concentrating tables for primary treatment, and two Card and one Wilfley for secondary. The middlings are passed through a classifier, whilst the coarser material is treated on a Wilfley table, and the fine on a Card table, the resultant residues being treated by a pulp thickener and then on a Card table. The plant was erected in December, 1914, and, although the water supply is limited, every effort is made to meet the public requirements. Delays naturally occur, due either to the limited water supply, or an extra rush of parcels of ore for treatment, but there is no doubt that this battery is capable of dealing with all public crushings from the field. As the “ alluvial ground ” has been dealt with at some length in the earlier part of this paper, no further mention need be made. Bygoo Group. This end of the Ardlethan field is situated from 3 to 4J miles north-west of the C’arpathia group, Bygoo being the first tin-bearing area, and Little Bygoo, 1J miles further on, the next exposure of stanniferous rock. There is no doubt that some good returns of tin were obtained in the early days of the field from surface “ bungs of ore, but at the present the working propositions appear to be dependent more upon the recovery of tin from belts of comparatively low-grade material. Although the presence of porphyry has not yet been proved at this group of mines, judging by the nature of the occurrences, there is little doubt that they owe their origin to an intrusion of that rock, and the writer fully expects that it will be reached at no great depth. The Big Bygoo property embraces an area of mineral-bearing leasehold which includes the original Big Bygoo leases, the Lone Hand, and adjacent areas. Here w~e find six separate outcrops of a highly siliceous type of granite, surrounded on three sides by a more or less basic type, in which felspars predominate. This company is at present winning ore from several belts of altered granite,, the most easterly one of which has an area of approximately half an acre. Two shafts have been sunk on this to a depth of 90 and 70 feet respectively, and connected by a level 60 feet long. Very little stoping has been done, but good parcels of ore were obtained from the shafts, &c. Much of the material present in this occurrence is almost entirely composed of silica, and in addition to the tin contents, very large makes of tourmaline occur. The ore now mined averages about 5 per cent, tin, and is free from im¬ purities. Up to the present the ore has been carted to the Southern Cross battery, at the C’arpathia group of mines, some 6 miles distant. Under these circumstances only the richer bunches were worked. At the present time a 10-head stamper battery and the necessary concen¬ trating plant (ten tables) is being erected near the centre of this group of tin occurrences, and a tank to conserve water, with a capacity of 3,000.000 gallons has been excavated 1J miles from the battery, but, ow ing to the absence of rain, it is still dry. Some 35 chains south-west of the shafts referred to, a Big Bygoo Mine. L '?'f ^•44 l L. 29 belt of tin-bearing siliceous granite is being worked by open cut. This occurrence is approximately half an acre in extent, and, up to the present, bulk crushings point to the average tin contents being in the neighbourhood of 2 per cent, of metallic tin. About 15 chains south of the open cut, the same company are prospecting a belt of siliceous granite, originally known as Coote’s Lone Hand mine. Two shafts were sunk to a depth of 65 and 50 feet respectively, and now several open cuts are being exploited. In places there is a somewhat high percentage of bismuth present, but large bunches of high-grade tin ore were recovered in the early days, and from the nature of the country rock further makes of payable ore mav be expected. The dimensions of the open cut now being worked are 16 feet by 20 feet, and the average recovery amounts to slightly over per cent, of metallic tin. The following are the returns of tin won from the Bygoo group of mines, as published in the Annual Reports of the Department of Mines :— 1913. —From the Big Bygoo 44 tons of ore yielded 5 tons of concen¬ trates, which returned £541, leaving 33 tons valued at £200 at grass. Dumbrell’s private lands lease (known as Dumbrell's Bygoo) gave some very rich ore, 14J tons realising £400, with a quantity of low- grade ore at grass. G. Coote’s Lone Hand raised 600 tons, estimated at 3 per cent., all now at grass. 1914. —At Bygoo George Corner raised 58 tons, and treated 30 tons for a return of £685. George Coote (Lone Hand mine) raised 300 tons during the year, of which 99 tons produced tin valued at £287. 1915. —Several crushings from Bygoo treated at the Southern Cross battery have been very satisfactory, and encouraged the lessees to do further prospecting. 1916. —The other producers are as follows :—Big Bygoo, £1,000; Lone Hand, £605 ; Dumbrell’s Bygoo, £400. 1917. —At Big Bygoo the developments have been most gratifying. At the end of the year ore to the value of £6,782 had been won. The Lone Hand produced £875 worth of concentrates. At Little Bygoo over £2,000 worth of concentrates have been produced in less than a month. 1918. —During 1918 the Big Bygoo mine yielded 1,303 tons of ore, valued at £10,121, the average value being nearly £8 a ton. The Lone Hand mine has been acquired by W. Litton, and 167 tons returned concentrates realising £650. Little Bygoo has produced nearly £5,000 worth of ore. Drumlish Hill. Within P.M.L. 113, parish of Yalgogrin, about half a mile south-west o Little Bygoo, a lode of tin-bearing material has been w r orked over a short- length down to a depth of 40 or 50 feet, and traced on the surface for about, a quarter of a mile. 30 The main ore body is up to 2 ft. 6 in. wide, and it is understood that good tin returns were obtained from the comparatively small tonnage of ore won. Parallel to the main lode, three veins up to 3 inches wide are exposed in the face of an open cut, over a width of about 6 feet, which also contain tin values. On close examination it is seen that the main lode occurs along a fault plane, the permeating solutions having almost entirely replaced the normal granite on the footwall side. The parallel veins, consisting mainly of dark coloured quartz with a little cassiterite, are considered to be due to deposition along sympathetic lines of stress. This type of occurrence is probably identical with the lode worked by the 40-feet level at the White Crystal mine, and they are the nearest approach to true fissure veins found on the field, but will probably not extend into the porphyry as such, for it is considered that that intrusion was the cause of the faulting. Little Bygoo, or Dumbrell’s Bygoo. This belt lies a little over a mile N.N.W. of Big Bygoo, and here three exposures of tin-bearing highly “ acid ” granite have been located. The largest of these covers about 2 acres, and has been opened up by shafts, trenches, and open cuts. Some rich “ bungs ” of tin ore were worked in the past, but the present holders are now treating low-grade ore recovered from the old open cuts and trenches. The remaining two occurrences are smaller, and up to the present have not yielded much tin. They are not quite so acid in type, but deeper sinking might lead to satisfactory results. In the writer's opinion all are identical with those in other parts of the Ardlethan field, and if bulk parcels of unpicked ore prove that a recovery of even 1J per cent, of tin can be made, there appears to be a large tonnage of ore available which could be worked by open cut. Economic handling, an up-to-date treatment plant, and an adequate supply of water are essential, however. The present treatment plant consists of a 5-head stamper battery (750 lb. per stamp), discharging through a 14-mesh screen on to two concentrating tables, the treatment capacity being 5 tons per shift. The plant was started in August, 1918, but owing to an inadequate water supply, very broken time has been worked. Returns furnished by Mr. Dumbrell (part owner) are as follow :— 1918 (three months’ work).—340 tons treated for a return of 5 tons 17 cwt. 2 qr. 21 lb. of 68 per cent, concentrates. 1919 (24th February to 20th March).— 80 tons treated for a return of 2 tons 5 cwt. 1 qr. (wet) of 67 per cent, concentrates. (19th May to 28th June).—112 tons treated for nearly three tons of con¬ centrates. 31 THE PROSPECTS OF OBTAINING AN ADEQUATE SUPPLY OF SUB-ARTESIAN WATER. Owing to the limited rainfall in the Ardlethan district, the question of an adequate water supply is a continued source of trouble. The evaporation of water from dams or tanks is high, and whilst some of the mining companies have excavated capacious tanks with good catchment areas, it is probable that if large treatment plants are to be kept running, a further source of supply would be necessary. The presence of sub-artesian water in this area has been proved by the New Venture Company’s bore, already referred to, and theoretically there is no reason w T hy other bores should not prove successful if put down in the right places. The site of the present bore was chosen by a divining-rod expert, and is near the top of a hill, so that without realizing the existing geological con¬ ditions, it would appear to be a most unlikely spot. The accompanying diagrammatic section indicates the conditions existing, and should only need a short explanation. Diagram. East West Ideal Section Illustrating probable conditions wth regard to sub-artesian water Sedimentary shown thus Granite " 4 cn i-±. d Porphyry shown thus A and B Bores - e. F.U.S.. Government Geologist. Department of Mines, Sydney, New South Wales, 1919 Scale t. '° 2 .° - 40 50 |° to eo Chains W K8T SECTION ON LINE A B Horizontal Scale 2 £2—22—2° Chains Vertical Scale 0 mo ape 6y Q p ee t Cr an/te shown thus Porphyry * •• IH East shown thus 71270 Alluvium shown thus PHOTO'LITHOQRAPHEO BY W A OULLICK. QOVT PRINTER N W