I 
 
 & EHHHBBBBBB^DBHHBfll 
 

 State Mining Bureau. 
 
 / 
 
 HENR Y G. HANKS, State Mineralogist. 
 
 CONTRIBUTIONS 
 
 TO THE 
 
 Geology and Mineralogy 
 
 OF 
 
 CALIFORNIA. 
 
 ON THE MILLING OF GOLD QUARTZ, 
 
 By MELVILLE ATT WOOD, R G. S. 
 
 SACRAMENTO : 
 
 J. D. YOUNG, :::::: SUPT. STATE PRINTING 
 1882. 
 
State Mining Bureau 
 
 HENR Y G. HANKS, State Mineralogist. 
 
 CONTRIBUTIONS 
 
 TO THE 
 
 Geology and Mineralogy 
 
 OF 
 
 CALIFORNIA. 
 
 ON THE MILLING OF GOLD QUARTZ, 
 
 Bv MELVILLE ATT WOOD, F. G. S. 
 
 SACRAMENTO : 
 
 j. D. YOUNG, ::::::: SUPT. STATE PRINTING, 
 1882. 
 

 
 
On the Milling of Gold Quartz. 
 
 HENRY G. HANKS, State Mineralogist: 
 
 DEAR SIR : My last paper to the State Geological Society 
 on " The Milling of Gold Quartz," wherein I tried to describe 
 the process of simple amalgamation of the raw pyritic matter 
 in wooden barrels, appears from the great number of letters 
 that I have received respecting it, after its publication in the 
 Mining and Scientific Press, to have attracted considerable 
 attention, and has, therefore, encouraged me to resume the 
 subject, but this time as a contribution to the State Mining 
 Bureau ; you having kindly offered to allow the specimens 
 accompanying this paper, and intended to illustrate what I 
 have stated, to remain for a short time at the rooms of the 
 Mining Bureau, to give those who feel interested in the mat- 
 ter a chance of examining them. You have also promised to 
 put some very important and interesting specimens from 
 your private collection with them. 
 
 I can only now repeat what I have stated on a former 
 occasion, that at the present time I think scarcely anything 
 can be of greater importance to the mining interests of this 
 State, than a simple and cheap mode of extracting the gold 
 from low grade veinstone, and the determination of the true 
 condition of the ores associated with it. 
 
 THE "FREE GOLD," 
 
 As it is called, can easily be saved ; indeed, the language of 
 the old mill-man, " only give it a chance and it will take care 
 of itself," is very true, particularly so when met with, as it is 
 in some of the Bodie veins, carrying scarcely any pyritic 
 matter. The difficulty in the concentration of the sulphurets 
 (I use the Californian term, which, as I stated before, was, I 
 think, first applied in Nevada County, in 1859, to the pyritic 
 matter associated with the quartz in the gold-bearing veins 
 
 242648 
 
- 4 - 
 
 of this State), appears now to be, in a great measure, over- 
 come by the use of the ' " Frue concentrator," which, with 
 comparatively little attention, and at one operation, makes 
 very clean work. I have served a very long apprenticeship 
 in the "dressing" of different kinds of ores, but in all my 
 experience never remember any machine which pleased me 
 better than the " Frue." The rubber surface of the revolving 
 cloth appears to greatly assist the operation. 
 
 The question of concentration being now so far solved, it 
 renders it desirable, indeed necessary, for isolated mills to 
 have some cheap and easy mode, which they can use at their 
 own works, to extract the gold from the concentrations. 
 
 TREATING PYRITES FOR THE EXTRACTION OF ITS GOLD. 
 
 The following is a copy of a paper on " Iron Pyrites," read 
 before the Royal Society of New South Wales, in 1874, by 
 J. Latta, Esq., which contains much valuable information : 
 
 MR. PRESIDENT AND GENTLEMEN : At the request of some of 
 the members of the Royal Society, I have ventured to occupy part 
 of your time this evening in describing the method of treating pyrites 
 for the extraction of its gold, as carried out by the Port Phillips 
 Company, at Clunes. 
 
 In 1 86 1 I was engaged by that company as their chemist and 
 assayer, with special instructions to devise, if possible, a process for 
 profitably extracting the gold from their pyrites, which was then but 
 little better than a waste product. Except processes inapplicable to 
 our circumstances, such as smelting, etc., the only known means for 
 extracting gold from such mineral was that practiced in South 
 America and the United States " of exposing the auriferous sul- 
 phides to the action of air and moisture for a year or so, whereby a 
 portion of the mineral became oxidized, liberating the gold previously 
 inclosed by the sulphides ; the mineral was then passed through the 
 stamping battery with quartz, and whatever portion of the sulphides 
 remained undecomposed was retained, as well as the then rude 
 machinery for that purpose admitted, to undergo another term of 
 oxidation, and so on whilst any remained." I scarcely need to point 
 out how extravagantly wasteful of time and gold such a process must 
 have been. Yet even at the present time this process is occasionally 
 practiced in Victoria. At some claims the blanketings that is, the 
 pyritous sand, with a little free gold caught upon the blankets are, 
 after a time, again put through the batteries with the quartz, for the 
 purpose of extracting its gold. Any one practically acquainted with 
 the treatment of mineral containing fine gold by the battery process, 
 will at once recognize the impossibility of retaining a fair proportion 
 of such minutely divided gold as oxidized pyrites affords ; by far the 
 
larger portion would be held in suspension by the water, and be 
 carried away by it through all the appliances devised for its retention. 
 In addition to the difficulty of retention arising from the fine state of 
 division which gold so obtained possesses, most of these particles 
 would be 
 
 COATED WITH IRON OXIDE, 
 
 and other products of the decomposed mineral, thus offering another 
 hindrance to its chance of amalgamating with the mercury. This 
 latter difficulty deserves careful consideration, where fine gold has to 
 be dealt with, as from its fineness it escapes the scrubbing which the 
 larger grains receive from contact with the quartz whilst crushing, 
 whereby their surfaces are cleaned, and thus rendered extremely 
 sensitive to the influence of mercury placed for their detention. In 
 reference to the condition of the gold inpyrites, it li,s come to be 
 pretty generally admitted that 'nearly, if not quite, all the gold exists 
 in the metallic state.' " 
 
 This qui^te agrees with the results of some experiments carried out 
 by myself in conjunction with Mr Daintree, late of the Victoria geo- 
 logical staff. Our researches ended in obtaining but the barest pos- 
 sible evidence of 
 
 GOLD EXISTING IN A MINERALIZED STATE IN PYRITES. 
 
 As a matter bearing somewhat in support of this result, and whilst 
 engaged in these investigations, I had the good fortune to come 
 across some fine specimens of cubical pyrites, which upon examina- 
 tion with a pocket lens, seemed to indicate the presence of gold ; 
 upon transferring them to a good microscope, gold was distinctly seen 
 upon the planes of cleavage, and upon dissecting the crystals, every 
 cleavage face was found distinctly gilded. Now, from the fact that 
 the presence of gold could only be determined by the aid of a good 
 microscope, and that only as a fine gilding, some notion may be 
 formed of the excessively fine state of its division, and how unsatis- 
 factory would be the task of separating such liberated films from* 
 water in motion. 
 
 Guided by these considerations it became evident that any attempt 
 to mechanically separate gold from pyrite unless aided by the 
 previous decomposition of its enveloping sulphides must prove 
 ineffective from the impossibility of reducing it to its ultimate atoms, 
 for so long as a cluster of sulphide atoms remain unbroken, they 
 might reasonably be imagined to enclose those of gold. Again, it 
 was equally clear that, when such gold was liberated from its enve- 
 lope, water concentration alone was inapplicable. To test the cor- 
 rectness of these conclusions, each of them was made the subject of 
 rigid experiment on an extended scale, . before receiving them as 
 fundamental truths to guide us in determining the best method 
 suitable to our requirements. Two parcels of pyrites of twenty tons 
 
- 6 - 
 
 each one roasted, the other unroasted were ground in one of the 
 best arastras known, with mercury ; a constant stream of water flow- 
 ing through to carry off the finely ground sand, which was then 
 carried through mercury boxes and over blankets. Each parcel 
 received the same amount of grinding and treatment in every detail. 
 The results are as follows : 
 
 Twenty tons raw sand containing 3 oz. 6 dwts. per ton: 
 
 Gold obtained 29.21 per cent. 
 
 Gold in tailings 42.84 per cent. 
 
 Gold carried off in water 27.95 per cent. 
 
 Twenty tons roasted sand, 1 oz. 7 dwts. 10 grs. of gold per ton: 
 
 Gold obtained 51.57 per cent. 
 
 Gold in tailings 27.21 per cent. 
 
 Gold carried off by water 21.22 percent. 
 
 Here it will be observed that, with the raw sand, only a small por- 
 tion of the gold was obtained a very much larger was left in the 
 tailings, although finely ground, and a large proportion was carried 
 off with the water as slime. With the roasted mineral more than 
 half the gold was obtained ; the tailings were much poorer than 
 those from the raw sand, but still very rich, and a large quantity was 
 carried off by the water. 
 
 After carefully considering the merits of the various methods sug- 
 gested for extracting gold from pyrites, our first problem to solve was 
 how to best destroy the enveloping sulphides and arsenides, so as to 
 get rid of the deleterious action of these minerals upon the mer- 
 cury used for amalgamating and detaining the liberated gold; and, 
 secondly, the best method of extracting the gold from the decom- 
 posed pyrites. After a number of experiments on a large scale, it 
 was decided to effect the decomposition of the pyrites by a roasting 
 process. To effect this economically, I devised, and, in conjunction 
 with Mr. H. A. Thompson, patented, in 1862, the inclined roasting 
 furnace, which is now used in many places throughout the Colonies. 
 It consists of an inclined roasting hearth, usually about 30 feet long 
 'by 5 feet wide; the fire-hole for heating the hearth on the lower end 
 of it, and is separated from it by the fire bridge; between the latter 
 and the hearth is a channel for conveying into the store-pit the sand 
 when roasted. In the foot wall of the furnace are 6 tubes, from i^ 
 to 2 inches diameter, for supplying heated air to the roasting sul- 
 phides; scarcely any air is admitted through the fire bars, the gas- 
 eous vapors from the fuel being completely burned by the great 
 excess of air passing over the fire for oxydizing the pyrites. Along 
 each side of the furnace are five working doors, for the workmen to 
 turn and rake down the mineral. Above the upper end of the fur- 
 nace a large hopper is constructed, capable of holding 24 hours' 
 supply of sand; in the floor of this hopper is a trap for supplying 
 mineral to the hearth ; the hopper is filled by trucks communicating 
 with the puddles by a tramway to the stamp-house. The whole of 
 
- 7 - 
 
 the furnace is carefully braced with vertical, longitudinal, and trans- 
 verse ties. The present furnace has been working about ten years, 
 and, with fair treatment, will last many years more. In working this 
 furnace the whole of the hearth is covered with pyrites to the depth 
 of between 2 and 3 inches, kept at a gentle red heat, with frequent 
 stirring, until the mineral nearest the fire, and about 6 feet beyond 
 it, is found no longer to give off sulphur fumes. An experienced 
 workman can determine when this condition has been attained by its 
 appearance in the furnace. It is then raked into the discharge chan- 
 nel and the mineral lying upon the hearth immediately above that 
 removed, is brought into its place ; again, that still further up is 
 brought a stage lower, until the whole has been shifted, when the 
 vacant place at the upper part is refilled from the hopper. The 
 sulphurous and arsenical vapors, together with the products of com- 
 bustion and dust from the pyrites, pass jnto a tunnel between 200 
 and 300 feet long, 4 feet high, and 3 feet wide, carried up the side 
 of a hill, terminating in a chimney 30 feet high. Nearly all the sand 
 and dust carried over by the draft is deposited within 40 feet of the 
 furnace, and is periodically removed for retreatment, as it contains a 
 notable quantity of gold; beyond 40 feet the sand is worthless. From 
 the size of the tunnel the vapors move slowly onward, and have, 
 consequently, time to deposit any heavy particles; continuing their 
 course, the vapors pass through 6 cellular brick screens, down which 
 a powerful spray of water passes; here they get cooled and scrubbed, 
 the sulphurous and sulphuric acids dissolved out, whilst the arsen- 
 ious acid is deposited on the floor of the tunnel, scarcely anything 
 escaping from the chimney but the foul vapors. Some alarm was 
 felt by the Town Council lest any 
 
 ARSENICAL VAPORS 
 
 Should escape and prove injurious to the inhabitants, as the works 
 were close upon the township, and they placed the matter in the 
 hands of Mr. Johnson, the Government analytical chemist, for inves- 
 tigation, who reported as follows: "I drew five gallons of the vapors 
 from the chimney of the roasting furnace, and, by the application of 
 one of the most delicate tests known to science, viz., Reinck's test, 
 discovered but the merest trace of arsenic." I may remark that 
 when this investigation took place we were condensing over two tons 
 of arsenic per month in the tunnel. I have dwelt somewhat length- 
 ily upon this part of my subject, as I am desirous to show that, with 
 due 'precautions, such operations can be safely carried on. in the 
 neighborhood of habitations. 
 
 In carrying out the roasting operations the work is divided into 
 three shifts of eight hours each, one man being able to attend a fur- 
 nace, and finally to cover up the hot sand discharged with damp 
 sand and spray it with water. This quenching was found to be a 
 matter of some importance, as the quartz sand always found with 
 
- 8 - 
 
 the pyrites is thereby broken up and rendered friable, by which the 
 after process of grinding is greatly facilitated. The quantity of sand 
 which a furnace of the above-mentioned size can treat, will average 
 4 tons per 24 hours, with a consumption of 3-10 of a cord of wood 
 per ton. Having determined upon a 
 
 MECHANICAL PROCESS FOR EXTRACTING THE GOLD 
 
 From the roasting mineral, it became necessary to discover the best 
 condition for accomplishing it. In this, also, we were greatly assisted 
 by the knowledge gained of the physical condition of the gold in 
 pyrites. Consequently, after our earlier experiments already men- 
 tioned, we carefully avoided a current of water, and ground with 
 mercury without an overflow until it was considered the gold had 
 become amalgamated. By cautiously varying the experiments, and 
 ascertaining the proportion of gold obtained in each case, we were 
 led up to the present method of working. From the results of a 
 great number of experiments, it was shown that the quantity of water 
 used in the grinding process was a matter of considerable importance, 
 the success of the operation to a great extent depending upon the 
 sand being in a damp condition only; by this means the mercury 
 becomes thoroughly diffused, and every grain of sand has a particle 
 of mercury in contact with it ; consequently there is afforded abun- 
 dant opportunity for the gold to amalgamate. On the other hand, if 
 sufficient water has been used to convert the mass into a semi-fluid 
 state, the mercury remained at the bottom of the mill, the surface 
 only being in contact with the sand; consequently the opportunity 
 for amalgamation was considerably lessened, and the quantity of gold 
 extracted very much less than when working damp sand only. As 
 the result of these experiments, the following process has been 
 adopted : The sand, after being roasted, is ground only moderately 
 damp with an equal weight of mercury for three quarters of an 
 hour, under the rollers of an ordinary Chilean mill; water is then 
 allowed to flow into the basin, the mill still revolving, until nearly all 
 the finely ground sand has been carried off in the overflow to the 
 concentrator; the mill is then stopped, the water drained off from 
 the unground sand and mercury, again started, and recharged with 
 fresh sand, and so on until it is necessary to clear out the amalgam- 
 generally once a week, depending upon the richness of the mineral 
 treated. The finely ground sand passed into the concentrator is kept 
 slowly stirred for a quarter of an hour, to keep the sand in suspen- 
 sion in the water, and allow the mercury and any amalgam which 
 might have been carried over from the mill to gravitate through it; 
 the water with its sand is then slowly run through a smaller concen- 
 trator, to retain any valuable particles which might have escaped the 
 first, and is then .considered sufficiently impoverished to be allowed 
 to run away. 
 
 The quantity of roasted mineral the company treat by this process, 
 
- 9 - . 
 
 when working, averages 18 tons per week the duty of two mills 
 worked in eight-hour shifts, one man attending them, alternately 
 changing and discharging. 
 
 THE AVERAGE PROPORTION OF GOLD EXTRACTED 
 
 During the last year, from 294 tons of pyrites, amounted to 95.19 
 per cent, of the assays, the sand averaging 4^ ounces of gold per 
 ton. Some of the parcels returned as high as 98 per cent, during 
 that period. The cost of extraction amounted to 2 2s. 4d. per 
 ton, without estimating wear and interest on capital. The above 
 charge is rather high, as fuel during that period was unusually dear, 
 and the furnace being but 4 feet wide, instead of 5 feet, increased 
 the labor cost, as less work is done at the same cost than would be 
 incurred in working a larger furnace. Another element in the cost 
 is the mercury which is lost, amounting to i pound and 13 ounces 
 per ton a large proportion of which, I think, might be saved by 
 improved appliances for that purpose, together with the gold con- 
 tained in it. The immediate cause of this loss of mercury is the 
 severe trituration to which it is subjected with the sand. This was 
 found indispensable, for whenever, through oversight or experiment, 
 a less degree of trituration was applied than that now used, or the 
 sand ground too wet, th return of gold was invariably diminished 
 by several per cent. 
 
 In carrying out these operations, I found that a Targe proportion 
 of galena in the mineral seriously interfered with the extraction of 
 the gold, but a small proportion of the sulphides of copper, zinc, 
 or lead produced no appreciable effect. 
 
 Taking the process as it stands, we have been unable to find one 
 that would at less cost extract the same proportion of gold, or could 
 be safely trusted in unskilled hands with only occasional supervision. 
 
 Mr. Thompson also read the following return : 
 
 Returns of pyrites treated at the Port Phillip Company's works, 
 Chines, since October, 1866. Minerals treated: 1867, 215 tons, 17 
 cwt; 1868, 366 tons, 9 cwt.; 1869, 401 tons, n cwt; 1870, 431 
 tons, 9 cwt.; 1871, 561 tons, 2 cwt.; 1872, 368 tons, 6 cwt.; 1873, 
 294 tons. Gold, contents per ton, per assay: 1867, 4 ozs. 16 dwts. 
 6.93 grs.; 1868, 3 ozs. 18 dwts. 6.56 grs.; 1869, 4 ozs. i dwt. 19.15 
 grs.; 1870, 3 ozs. n dwts. 4.34 grs.; 1871, 4 ozs. 7 dwts. 10.99 g rs -j 
 1872, 5 ozs. 18 dwts. 19.36 grs.; 1873, 4 ozs. 10 dwts. 16.30 grs. 
 
 Total gold obtained: 1867, 960 ozs. 13 dwts.; 1868, 1,322 ozs. 
 13 dwts.; 1869, 1,515 ozs. IT dwts.; 1870, 1,370 ozs. 4 dwts.; 1871, 
 2,290 o_s. i dwt.; 1872, 2,031 ozs. 9 dwts.; 1873, 1,268 ozs. 17 
 dwts. 12 grs. 
 
 Gold extracted, per ton: 1867, 4 ozs. 9 dwts.; 1868, 3 ozs. 12 
 
- IO - 
 
 dwts. 4 grs.; 1869, 3 ozs. 15 dwts. 11.60 grs.; 1870, 3 ozs. 3 dwts. 
 12.60 grs.; 1871, 4 ozs. i dwt. 15.20 grs.; 1872, 5 ozs. n dwts. 
 22.56 grs.; 1873, 4 ozs. 6 dwts. 7.63 grs. 
 
 Percentage of gold extracted: 1867, 92.43; 1868, 91.71; 1869, 
 92.28; 1870,89.24; 1871,93.34; 1872,94.22; 1873,95.19. 
 
 The results obtained by Mr. Latta appear to have been 
 exceedingly close and satisfactory, though rather costly 
 about ten dollars per ton which, I think, could have been 
 much lessened had the stuff been reduced finer, and the con- 
 centration been carried a little further, so as to have freed 
 the pyrites from the excess of gangue or quartz sand pre- 
 vious to calcination. 
 
 It is now generally admitted by metallurgists of any note, 
 that the gold in pyrites exists in a metallic state, and it is 
 with no little pleasure that I am enabled to practically cor- 
 roborate the statements of Mr. Latta on this subject, having 
 procured for your inspection a number of crystals, and frag- 
 ments of crystals, of auriferous pyrites, obtained from different 
 parts of this State. They are mounted on glass slides for 
 microscopic examination, as with a common lens the pres- 
 ence of the gold can hardly be detected ; but with a good 
 microscope, using an inch or half inch objective, it will be 
 found that the faces of some of the crystals are, in places, 
 most finely and beautifully gilded, and that here and there 
 are seen little specks or drops of gold partially imbedded in 
 the pyrite. The mill-man, after looking at these specimens, 
 will not be surprised at the loss sustained in the wet stamping 
 of auriferous pyrites. 
 
 SAMPLING AND ASSAYING GOLD QUARTZ. 
 
 In Phillip's Metallurgy, pages 166 and 167, very good 
 directions are given for sampling and assaying gold quartz. 
 For assaying, he says: "The most accurate results are 
 obtained by carefully washing a four-pound sample in the 
 batea. After having in this way concentrated the gold in 
 about an ounce of sand and pyrites, this residue may be 
 either subjected to assay, or the sulphides dissolved by nitric 
 acid, and the gold extracted by amalgamation with mercury, 
 which is subsequently volatilized, and the gold weighed. In 
 either case, calculations are made on the four-pound sample, 
 and when the residue has been subjected to fusion, very 
 accurate results are obtained." 
 
- 1 1 - 
 
 BARREL AMALGAMATION. 
 
 During the time I was engaged in gold mining in Brazil, I 
 stayed for some time at the St. John del Rey mine, and there 
 witnessed the barrel amalgamation which I described in my 
 last paper to the State Geological Society, and which is repro- 
 duced here: 
 
 Their process of amalgamation is nearly perfect, but the stamping 
 and concentration very defective, the stamps doing but little duty 
 only \y^ tons per head during the 24 hours; their plan of concen- 
 tration being principally what is called "straking," consisting of a 
 number of fixed inclined trays 30 feet in length and 18 inches wide, 
 with a fall of one inch to the foot. The trays are covered for the first 
 1 6 feet with bullocks' skins tanned with the hair on them, and in 
 lengths of 2 feet 2 inches; below these are series of blankets or 
 baize cloths of the same length. The deposit of sulphurets on 
 the first three skins contains nearly all the gold, and amounts to 
 about 0.42 of a cubic foot per ton of veinstone stamped. It con- 
 tains about 30 ounces of gold per ton, all of which, with the 
 exception of one ounce, is in a free state; the ounce of gold being 
 mechanically mixed with the coarser grains of pyrites. 
 
 It is estimated that in stamping and straking, 10 per cent, of 
 the total amount of the gold is carried off in suspension by the 
 water. 
 
 Their loss in amalgamation is comparatively trifling, as far as I 
 can gather from their numerous reports, and will average less than 
 4 per cent.; the loss of mercury is 0.45 ounces per cubic foot of sul- 
 phurets amalgamated. The apparatus employed for amalgamation 
 of the sulphurets consists of wooden barrels 4 feet in length and 2 
 feet 5 inches in diameter, having a capacity of 20 cubic feet. The 
 charge of sulphurets for each barrel is one ton and a half, free from 
 decomposition, and 60 pounds of mercury. There is also a sufficient 
 amount of clean water at the same time introduced to give the slimes 
 the necessary degree of fluidity to enable the globules of quicksilver 
 formed to become properly incorporated, without allowing them to 
 become sufficiently mobile to admit of the settling of the mercury 
 and amalgam at the bottom. The barrels, when charged, are allowed 
 to rotate from 20 to 30 hours, making 18 revolutions per minute, in 
 accordance with the state of the atmosphere. 
 
 The contents of the barrels are afterwards washed in an appa- 
 ratus called a " saxe," which is used to separate the gold amalgam 
 from the refuse. In this country it might be perhaps better to 
 employ separators the same as those used in the different pan 
 mills. 
 
 In their report of 1880 the results of their trials of 
 
- 12 - 
 THE COMSTOCK PAX SYSTEM 
 
 Was anything but satisfactory ; indeed, in the milling for gold that 
 system appears to be too costly for low-grade ores, and not fit for the 
 rich. It is better calculated for the treatment of veinstone which 
 contains in the ton from five to ten ounces of silver, and that iri a 
 suitable mineralized condition as chlorides, etc. 
 
 The attempts to grind the sulphurets when they contain upwards 
 of 50 per cent, of pyritic matter, and to amalgamate the mechanic- 
 ally combined gold inclosed in the particles of pyrites, at the same 
 time and in the same pan, has not been attended with success from 
 the earliest attempts, some of which I witnessed in Brazil in 1832, 
 which was then made in an apparatus being a modification of the 
 Hungarian bowl. The St. John del Rey sulphurets when ready for 
 the barrel contain about 95 per cent, of pyritic matter, and are 
 reduced so fine that 90 per cent, of it will pass through a sieve 
 having 100 holes to the linear inch. 
 
 What I have tried of the California sulphurets the pyritic matter 
 varies from 70 per cent, to 90 per cent., and about 75 per cent, of it 
 will pass through a sieve of 100 holes to the linear inch. 
 
 The following analyses were made by John A. Phillips, F. G. S., 
 and published in his Metallurgy of Gold and Silver. I lately 
 received a letter from him, wherein he tells me he is going to pub- 
 lish another work on gold : 
 
 ANALYSES OF AURIFEROUS CALIFORNIA PYRITES CONCENTRATED 
 FROM TAILINGS BY JOHN A. PHILLIPS. 
 
 
 From 
 Grass Valley. 
 
 From 
 Near Sonora. 
 
 North Star, 
 Grass Valley. 
 
 Sulphur 
 
 46.700 
 
 37.250 
 
 43.720 
 
 Arsenic _ _ 
 
 .310 
 
 8.490 
 
 1.360 
 
 Iron 
 
 41.650 
 
 36.540 
 
 39.250 
 
 Copper 
 
 trace. 
 
 trace. 
 
 .220 
 
 T 1 
 
 Lead 
 
 trace. 
 
 .400 
 
 trace. 
 
 Gold 
 
 .037 
 
 .302" 
 
 .026 
 
 Silver 
 
 .OS6 
 
 ) 
 
 .012 
 
 Cobalt 
 
 .036 
 
 y Not determined. 
 
 .150 
 
 Silica 
 
 10.970 
 
 17.150 
 
 14.230 
 
 
 
 
 
 Totals. 
 
 99.703 
 
 100.162 
 
 98.968 
 
 Gold__ 
 Silver 
 
 PER TON OF 20 CWT. 
 
 Oz. 
 12 
 11 
 
 Dwt. Gr. 
 
 2 
 
 16 
 
 Oz. 
 93 
 
 Dwt. 
 13 
 
 Gr. 
 
 
 Oz. Dwt. Gr. 
 8 10 
 
 3 18 
 
- 13 - 
 
 By careful analysis their concentrations differ but little 
 from those of some of the mines near Sonora, Tuolumne 
 County, CaL, the amount of arsenic varying from one to ten 
 per cent., though in the upper part of the St. John del Rey 
 mine it did not contain so much arsenic as the following 
 analysis, made by John A. Phillips in 1847, shows. 
 
 Analysis of uncrushed ores from the St. John del Rey 
 mines, made by J. Arthur Phillips, in 1847 : 
 
 Silica 16.87 
 
 Carbonate magnesia 12.17 
 
 Carbonate lime 3.01 
 
 Sulphur (iron pyrites) ^ 16.78 
 
 Iron (iron pyrites) 14.65 
 
 Peroxide of iron 32.84 
 
 Peroxide of manganese 3.63 
 
 Arsenic and gold Traces. 
 
 99.94 
 N. B. Gold per ton equal 1 oz. 2 dwt. 20 gr. 
 
 The reason I have said so much about these mines, and 
 called your attention so frequently to them, is from the fact 
 of their successful treatment of such a difficult veinstone for 
 so many years. To properly understand the magnitude of 
 the work, suppose we estimate the yield of the veinstone in 
 California, from all the mines in pyritic matter, to be, say five 
 per cent, of all that is worked (which is rather high), it will 
 hardly equal that treated daily at the St. John del Rey 
 works. 
 
 The results of years of experience in working such a mine 
 ought to be interesting even if it were not exceedingly valu- 
 able, as it really is ; yet there are not wanting those who 
 object to any information obtained from the reports of such 
 as the St. John del Rey Company, on the (not very wise) 
 grounds of the mine being worked in Brazil, and the reports 
 printed and published in London ; and, may be worse than 
 all, that the dividends are, and have been for the last forty 
 years, paid there. In the 
 
 MILLING OF CALIFORNIA GOLD QUARTZ, 
 
 I would advise, for low grade rock, the stamping of it as 
 coarse as such a machine as the "Frue," or other improved 
 concentrator can treat to advantage. The size of the aper- 
 ture in the screens should gradually increase, and be the larg- 
 est in the upper part, which would in a great measure prevent 
 what is termed "dead stamping," and, at the same time, add 
 
greatly to the duty of the stamps. Screens having 12 holes 
 to the linear inch in the bottom and 10 in the upper part, 
 are not too coarse for low grade rock. As a stamp-head 
 weighing 8 cwt. will then, on an average, reduce 4 tons in the 
 24 hours,. and those of 6 cwt. about 3 tons, and any trifling 
 loss of free gold will amply be made up by what is saved in 
 the sulphurets so that a "Ten Stamp Mill" with heads weigh- 
 ing 8 cwt., can be made to ivork to advantage 4.0 tons of rock 
 per day. The fineness of the stamping, however, is in part 
 regulated by the position of the screen, that is, their hori- 
 zontal distance from the stamp-head and the vertical height of 
 the bottom of the screen above the level of the die. For 
 example, the finest work is done by splash-stamping, that is, 
 without using any screens, and allowing the pulp to be dis- 
 charged over the front side of the mortar, which is purposely 
 made lower than the back or feed part of the mortar. 
 
 The Port Phillip Company, in Australia, I believe, use 
 them with 10 holes to the linear inch. Steel wire-cloth is the 
 best and will, I am told, last better than any other. 
 
 Some years ago, in a communication to the State Geolog- 
 ical Society on the subject, I recommended fine stamping for 
 low grade rock containing a large proportion of sulphurets ; 
 but recent improvements in concentrators, and a closer exam- 
 ination of the condition of the gold in the iron pyrites, of 
 which I find so large a proportion is in thin films, and which, 
 with a rapid flow of water, would be carried away, and a 
 greater part, of it lost, have altered my opinion on this point. 
 
 It is not generally known, but nevertheless, from numerous 
 and very careful tests, it is proved that in fine stamping, 
 when the speed of the stamps is above seventy-five blows per 
 minute, that the loss of gold, when blankets or raw hides are 
 used, is much greater than at a speed of fifty blows per min- 
 ute; though I am not aware that any tests have been made 
 when the amalgamation was done in the battery. The sys- 
 tem of 
 
 AMALGAMATION IX THE BATTERIES, 
 
 However, I have always considered a mistake and as entails 
 ing a great loss of gold, particularly so, when the rock con- 
 tains a large proportion of sulphurets; besides, if precaution- 
 are not taken, a low degree of temperature will render the 
 amalgamated silver plates nearly useless. To understand 
 this correctly let the mill-man put two or three barrowfuls of 
 rock very rich in sulphurets through the stamps and then 
 watch the effect on the amalgamated plate, and at the same 
 
- 15 - 
 
 time collect some of the pulp after passing over the plates, 
 and have it carefully tested, and he will then better under- 
 stand why I prefer the blanket system. 
 
 Prof. W. W. Smyth, in one of his lectures on gold, with 
 respect to stamping, says : " Take a large hammer and gently 
 crack a nut with it, and you have an illustration^of what a 
 stamp ought to do; it ought, if possible, to crack the envel- 
 oping shell of stone, and set free the kernel of metallic min- 
 eral unbroken'."- 
 
 Or, for instance, take a piece of veinstone from the Bodie 
 district the same as marked No. 26 one half of it pound 
 very fine, using a grinding action with the pestle, then wash 
 out the gold in a batea, or horn spoon, and you will find that 
 a large proportion of the gold will float away, in spite of 
 every care, even using ammonia to destroy the grease on the 
 ends of the fingers. 
 
 Then take the other half, pound it very coarsely, and in 
 washing out the gold you will see very little float, and two or 
 three turns of the batea will bring all the gold into the center. 
 
 IN THE BLANKET SYSTEM, 
 
 Where improved concentrators are used, after the pulp has 
 passed over the blankets, only two lengths of trays of about 
 four feet each, and two sets to each five stamps are required. 
 They should be so arranged that the inclination can be 
 altered, say from 3 to 5, to suit the stuff being treated. 
 
 The trays should be about 16 inches wide, and the fall from 
 the battery box to the head tray the same as from one tray 
 to another, about 4 inches, with a board placed across the end 
 that the fall of the water or pulp will be so broken as to strike 
 the blanket in the tray below nearly at right angles. The 
 blankets should be in 3-feet lengths, and made of coarse wool 
 with a long nap. The double sets of trays are for the con- 
 venience of changing and washing the blankets. The blanket 
 washings can be passed through a simple machine like that 
 described in Phillips' Metallurgy (see page 185), and the tail- 
 ings from it ground with the coarse concentrations in a Chil- 
 ean mill. 
 
 It is not so much the length of the blankets that separates 
 the gold from the gangue, but the fall, or jump, on them. 
 
 Where the mill has a limited supply of water, and they do 
 not like to go to the expense of a number of concentrators, a 
 coarse concentrator may be made with a " Tye Buddie," the 
 
- 16 - 
 
 plans and directions for the use of which will be found in 
 "Phillips' Metallurgy of Gold and Silver," page 187. 
 
 The concentrations from the "Tye" can be passed over the 
 "Frue," one of which would then be sufficient for a large mill; 
 though I am not prepared to say by such means they can 
 work as closely as by using the "Frue" alone. 
 
 In case the mill is not situated at a very great altitude, 
 where the frost might interfere with this working, 
 
 AMALGAMATED PLATES, 
 
 In 3-feet lengths and 2 feet deep, on a fixed frame at an 
 angle of about 3, to which a slow lateral movement backward 
 and forward of orfe foot, together with a slight shake, is given, 
 in the same direction, with a sprinkling of clean water from a 
 perforated pipe falling on the upper part above where the 
 pulp strikes, might be placed with advantage between the 
 blankets and concentrators. 
 
 THE CONCENTRATIONS 
 
 Should be sifted through a seive having 80 holes to the linear 
 inch, and any particles that were not fine enough should- be 
 ground in a Chilean mill, the same as described by Mr. Latta, 
 but without using the mercury; and afterwards charged into 
 wooden barrels for amalgamation; but, before charging, the 
 sulphurets should be soaked in water, to free them from all 
 decomposition. I feel confident that larger results will be 
 obtained by thus treating the raw ore than if it was roasted. 
 The great difference between a wooden surface and a metal 
 one in amalgamation can easily be shown by washing out, say, 
 about one dwt. of Bodie or Grass Valley gold in a batea and 
 then adding, with a dropping bottle, just sufficient mercury 
 for it to amalgamate jvith too much or too little will lengthen 
 the result ; but if the proper quantity be used, by rubbing it 
 with the finger in the center of the bowl it will amalgamate 
 rapidly in less than a minute. Try the same experiment with 
 an iron pan, and you will find how much longer it takes to 
 get the same result. I would strongly recommend any mine 
 adventurer, before erecting any quartz mill, or adopting any 
 particular process, to have some 20 or 30 tons of the rock or 
 veinstone stamped, and to save, during that operation, a fair 
 sample of the battery pulp from it, which should be carefully 
 concentrated in a batea, or any other utensil used for washing 
 on a small scale. The condition and quantity of the gold, 
 
and other ores and minerals, should be tested and examined. 
 The percentage of the sulphurets can also be roughly esti- 
 mated at the same time, and all afterwards compared with 
 the gross results from stamping. 
 
 TEST FOR TELLURIUM. 
 
 Mr. Edward Booth, analytical chemist, has kindly furnished 
 me with directions for making a simple test for tellurium, in 
 case telluric gold is suspected to be mixed with the sulphu- 
 rets. It is as follows : 
 
 "Place in a test tube, or other vessel capable of resisting 
 the action of acids, a small amount of the suspected material; 
 which has been separated as thoroughly as possible from the 
 accompanying gangue. Add enough sulphuric acid to well 
 cover the sample and heat to boiling. If tellurium is present 
 the liquid becomes colored a clear purplish red." 
 
 I have only found, as yet, telluric gold in two mines in 
 Nevada County one near Grass Valley, and the other, the 
 Murchie mine, near Nevada City. - 
 
 In my private collection I found a specimen marked 
 "Meadow Lake Ore." I do not /ecollect who gave it to me, 
 but it contains both gold and telluric gold. 
 
 REBELLIOUS GOLD ORES. 
 
 A great deal has been written and said about the so-called 
 rebellious gold ores of the Meadow Lake District, and what 
 the different process-m'en were going to do with them, but I 
 never remember having heard of any careful analysis being 
 made, either of the veinstone or the concentrations. I .would 
 therefore respectfully suggest to those who have any samples 
 of the Meadow Lake ores to donate them to the State Mining 
 Bureau, as the examination and determination of them would 
 be of the greatest importance to the mining interests of the 
 State. The mines were discovered, I think, in 1862, and in 
 1865 and 1866 eight quartz mills were erected; a large 
 town built, estimated to contain 5,000 inhabitants. Now the 
 place is quite deserted. 
 
 In the published reports of the Geological Survey, 1864, 
 by Professor Whitney, no mention is made of the mines or 
 district, so that little could have been known about them at 
 that time. 
 
- i8 - 
 
 THE PAN SYSTEM. 
 
 I can only now add, that had I years ago acted upon what 
 I now suggest to others, I would have saved large sums of 
 money for, my partners and myself. For instance, what is the 
 difference between the gold and sulphurets in the Mammoth 
 lode, Mono County, and in the Sierra Buttes lode? Is not 
 the gold in the latter much more difficult to save, and would 
 not the Comstock soda, salt, and pan system, if introduced at 
 the Sierra Buttes mine, soon close it up like the former? For 
 my own part, I firmly believe that' if the same pan system 
 were used in the Victoria District, Australia, all the mines 
 using it would soon cease to pay dividends; and, also, if the 
 Idaho mines at Grass Valley were to try it, that their divi- 
 dends would soon be reduced one half. 
 
 If the correct number of tons of mercury, soda, salt, and 
 "other chemicals," as they are called, that have been sent to 
 the Mono County mills were published, I am afraid it would 
 appear to be very large. 
 
 It might be urged that the chemicals used in the Bodie 
 mills were for the extraction of the silver from the ores. In 
 that case, it would be exceedingly interesting to ascertain the 
 expense, and see if it did not, as some think, cost $2 in coin 
 for every $i in silver so obtained. 
 
 CATALOGUE OF SPECIMENS. 
 
 The following is a catalogue of the specimens which I shall 
 place in the State Mining Bureau to illustrate this paper: 
 
 No. i Crystal of pyrite on a glass slide. Some of the faces are 
 very finely and beautifully gilded; so fine indeed that it requires an 
 inch objective to see it to advantage. From the Eureka mine, Grass 
 Valley. 
 
 Nos. 2, 3, and 4 Gold, in little drops or specks, imbedded in the 
 pyrites. From El Dorado County. 
 
 No. 5 A specimen of arsenical pyrites with gold. From a mine 
 near Nevada City. 
 
 Nos. 6 and 7 Sections cut from the same, in which the gold is 
 easily recognized. 
 
 Nos. 8 and 9 Gold, with telluric gold. 
 
 No. 10 Section cut from same. 
 
 No. ii Gold in carbonate of lime. P^ureka mine, Grass Valley. 
 
 No. 12 -Gold in talcose slate. Taquarilla mine, Brazil. 
 
 No. 13 Gold in talc. Placerville. 
 
 No. 14 Gold on talc. Brazil. 
 
- 19 - 
 
 Nos. 15 and 16 Gold in lacotinga (micaceous iron). Gongo 
 Soco mine, Brazil. The lac^irrja veins are from a few inches to 
 many feet in width. 
 
 Nos. 17 and 18 St. John del Rey veinstone; 18 is about the 
 average of what was milled in 1866. 
 
 No. 19 Specimen of killas from St. John del Rey mine; a rock 
 which forms the sides of the lode, but also contains considerable 
 pyrites. 
 
 Nos 20, 21, and 22 Sections cut from St. John del Rey vein- 
 stone for microscopic examination. 
 
 Nos. 23 and 24 Sections cut from the killas. 
 
 No. 25 Yellow dusty matter mixed with gold, taken out of one 
 of the richest pockets ever found at Grass Valley. 
 
 No 26 Veinstone with gold. Bodie District. 
 
 No. 27 Gold in country rock (diorite). From Nicaragua. 
 
 No. 28 Gold in quartz crystal. 
 
 No. 29 Gold in syenite. 
 
 No. 30 Section cut from No. 29. 
 
 I have cut a great number of sections from the St. John 
 -del Rey veinstone, but could not detect the gold in any of 
 them, and unless very great care is taken the batea test will 
 hardly show any gold ; notwithstanding which, on a large 
 scale, they obtain better results from the amalgamation of 
 the raw sulphurets than any other process I have seen tried. 
 
 THE TRIBUTE SYSTEM. 
 
 I have just received a copy of the report of the Port Phillip 
 Company, Australia, published January 13, 1881, by which it 
 appears the tribute system has been introduced there with 
 great success. Too much can hardly be said in favor of such 
 a system, as it places the hard working and intelligent miner 
 on a much more respectable and independent footing; and 
 though he in a measure shares the risks, but only so far as 
 his judgment guides him, he gets the benefit of any discovery 
 he may make. It also encourages him to study the peculiari- 
 ties of the lode and inclosing rocks ; besides which, by that 
 system, all are jointly interested in the welfare of the mine. 
 Many of the mines now idle in this State could be worked 
 profitably under the system, particularly in the Bodie district. 
 
 In the Port Phillip report it says: 
 
 The number of tributes has averaged about 200 during the year, 
 which shows no decrease when compared with the preceding year. 
 The tribute system has been further extended by an arrangement 
 
- 20 - 
 
 with the tributers to drive the levels in the ground let to them, the 
 company assisting them with driving timber and rails, and making 
 an allowance per fathom until the yield reaches 6 dwts. per ton, 
 when no further assistance is given; the company receiving half the 
 gold obtained, and deducting from the allowance the cost of tram- 
 ming. By this means a large amount of driving is done at a com- 
 paratively small cost. 
 
 The number of tons of quartz stamped on tributers' account 
 for the year was 48,184 tons. The average yield of the entire 
 quantity raised was 5 dwts. 5^ grains per ton (say $5). 
 
 Total receipts 82,364 14s 7cl 
 
 Expenditure 26,310 10s 7d 
 
 Leaving a profit of 0,054 4s Od 
 
 In conclusion, so thoroughly am I convinced of the great 
 benefits that would result to this State by a more general 
 introduction of the tribute system in an extended form, both 
 to the placer as well as vein mining, that I wish particularly 
 to call your attention to it, so that, through the influence of 
 the Bureau, the subject may be brought in a proper light 
 before the owners of mines or claims. A fair tribute will 
 secure the muscle of the working miner, who, in too many 
 cases, understands better than the Superintendent (generally 
 a man of business) how to conduct trials for ore, and after- 
 ward to develop them. The muscle of the skilled miner is in 
 every respect better than foreign capital. 
 
 There is no need of the hard-working miner to leave this 
 healthy climate in search of employment, if those who own 
 mines that are now idle would let the fact be known through 
 the press, and at the same time offer a fair tribute for working 
 them. 
 
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