Attwood, M. Milling of Gold Quartz, 1882

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State Mining Bureau./ HENR Y G. HANKS, State Mineralogist.CONTRIBUTIONS

TO THE

Geology and MineralogyOF

CALIFORNIA.

ON THE MILLING OF GOLD QUARTZ,By MELVILLE ATTWOOD, R G. S.

SACRAMENTO :J. D. YOUNG, :::::: SUPT. STATE PRINTING1882.


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State Mining BureauHENR Y G. HANKS, State Mineralogist.

CONTRIBUTIONSTO THE

Geology and MineralogyOFCALIFORNIA.

ON THE MILLING OF GOLD QUARTZ,Bv MELVILLE ATTWOOD, F. G. S.

SACRAMENTO :j. D. YOUNG, ::::::: SUPT. STATE PRINTING,1882.


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On the Milling of Gold Quartz.HENRY G. HANKS, State Mineralogist:DEAR SIR : My last paper to the State Geological Societyon The Milling of Gold Quartz, wherein I tried to describethe process of simple amalgamation of the raw pyritic matter

in wooden barrels, appears from the great number of lettersthat I have received respecting it, after its publication in theMining and Scientific Press, to have attracted considerableattention, and has, therefore, encouraged me to resume thesubject, but this time as a contribution to the State MiningBureau ; you having kindly offered to allow the specimensaccompanying this paper, and intended to illustrate what Ihave stated, to remain for a short time at the rooms of theMining Bureau, to give those who feel interested in the mat-ter a chance of examining them. You have also promised toput some very important and interesting specimens fromyour private collection with them.I can only now repeat what I have stated on a formeroccasion, that at the present time I think scarcely anythingcan be of greater importance to the mining interests of thisState, than a simple and cheap mode of extracting the goldfrom low grade veinstone, and the determination of the truecondition of the ores associated with it.

THE FREE GOLD,As it is called, can easily be saved ; indeed, the language ofthe old mill-man, only give it a chance and it will take careof itself, is very true, particularly so when met with, as it isin some of the Bodie veins, carrying scarcely any pyriticmatter. The difficulty in the concentration of the sulphurets(I

use the Californian term, which, as I stated before, was, Ithink, first applied in Nevada County, in 1859, to the pyriticmatter associated with the quartz in the gold-bearing veins242648


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larger portion would be held in suspension by the water, and becarried away by it through all the appliances devised for its retention.In addition to the difficulty of retention arising from the fine state ofdivision which gold so obtained possesses, most of these particleswould beCOATED WITH IRON OXIDE,

and other products of the decomposed mineral, thus offering anotherhindrance to its chance of amalgamating with the mercury. Thislatter difficulty deserves careful consideration, where fine gold has tobe dealt with, as from its fineness it escapes the scrubbing which thelarger grains receive from contact with the quartz whilst crushing,whereby their surfaces are cleaned, and thus rendered extremelysensitive to the influence of mercury placed for their detention. Inreference to the condition of the gold inpyrites, it li,s come to bepretty generally admitted that 'nearly, if not quite, all the gold existsin the metallic state.'

This qui^te agrees with the results of some experiments carried outby 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 comeacross 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 seenupon the planes of cleavage, and upon dissecting the crystals, everycleavage face was found distinctly gilded. Now, from the fact thatthe presence of gold could only be determined by the aid of a goodmicroscope, and that only as a fine gilding, some notion may beformed 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 attemptto mechanically separate gold from pyrite unless aided by theprevious decomposition of its enveloping sulphides must proveineffective from the impossibility of reducing it to its ultimate atoms,for so long as a cluster of sulphide atoms remain unbroken, theymight reasonably be imagined to enclose those of gold. Again, itwas 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 ofrigid experiment on an extended scale, . before receiving them asfundamental truths to guide us in determining the best methodsuitable to our requirements. Two parcels of pyrites of twenty tons


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- 6 -each one roasted, the other unroasted were ground in one of thebest arastras known, with mercury ; a constant stream of water flow-ing through to carry off the finely ground sand, which was thencarried through mercury boxes and over blankets. Each parcelreceived 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 carriedoff with the water as slime. With the roasted mineral more thanhalf the gold was obtained ; the tailings were much poorer thanthose from the raw sand, but still very rich, and a large quantity wascarried 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 washow to best destroy the enveloping sulphides and arsenides, so as toget 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, itwas decided to effect the decomposition of the pyrites by a roastingprocess. To effect this economically, I devised, and, in conjunctionwith Mr. H. A. Thompson, patented, in 1862, the inclined roastingfurnace, 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 endof it, and is separated from it by the fire bridge; between the latterand the hearth is a channel for conveying into the store-pit the sandwhen 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 greatexcess of air passing over the fire for oxydizing the pyrites. Alongeach side of the furnace are five working doors, for the workmen toturn 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 supplyingmineral to the hearth ; the hopper is filled by trucks communicatingwith the puddles by a tramway to the stamp-house. The whole of


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- 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 thisfurnace the whole of the hearth is covered with pyrites to the depthof between 2 and 3 inches, kept at a gentle red heat, with frequentstirring, until the mineral nearest the fire, and about 6 feet beyondit, is found no longer to give off sulphur fumes. An experiencedworkman can determine when this condition has been attained by itsappearance in the furnace. It is then raked into the discharge chan-nel and the mineral lying upon the hearth immediately above thatremoved, is brought into its place ; again, that still further up isbrought a stage lower, until the whole has been shifted, when thevacant place at the upper part is refilled from the hopper. Thesulphurous and arsenical vapors, together with the products of com-bustion and dust from the pyrites, pass jnto a tunnel between 200and 300 feet long, 4 feet high, and 3 feet wide, carried up the sideof a hill, terminating in a chimney 30 feet high. Nearly all the sandand dust carried over by the draft is deposited within 40 feet of thefurnace, and is periodically removed for retreatment, as it contains anotable quantity of gold; beyond 40 feet the sand is worthless. Fromthe size of the tunnel the vapors move slowly onward, and have,consequently, time to deposit any heavy particles; continuing theircourse, the vapors pass through 6 cellular brick screens, down whicha 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 anythingescaping from the chimney but the foul vapors. Some alarm wasfelt by the Town Council lest any

ARSENICAL VAPORSShould escape and prove injurious to the inhabitants, as the workswere close upon the township, and they placed the matter in thehands of Mr. Johnson, the Government analytical chemist, for inves-tigation, who reported as follows: I drew five gallons of the vaporsfrom the chimney of the roasting furnace, and, by the application ofone of the most delicate tests known to science, viz., Reinck's test,discovered but the merest trace of arsenic. I may remark thatwhen this investigation took place we were condensing over two tonsof 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, withdue 'precautions, such operations can be safely carried on. in theneighborhood of habitations.In carrying out the roasting operations the work is divided intothree shifts of eight hours each, one man being able to attend a fur-nace, and finally to cover up the hot sand discharged with dampsand and spray it with water. This quenching was found to be amatter of some importance, as the quartz sand always found with


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- 8 -the pyrites is thereby broken up and rendered friable, by which theafter process of grinding is greatly facilitated. The quantity of sandwhich a furnace of the above-mentioned size can treat, will average4 tons per 24 hours, with a consumption of 3-10 of a cord of woodper ton. Having determined upon a

MECHANICAL PROCESS FOR EXTRACTING THE GOLDFrom the roasting mineral, it became necessary to discover the bestcondition for accomplishing it. In this, also, we were greatly assistedby the knowledge gained of the physical condition of the gold inpyrites. Consequently, after our earlier experiments already men-tioned, we carefully avoided a current of water, and ground withmercury without an overflow until it was considered the gold hadbecome amalgamated. By cautiously varying the experiments, andascertaining the proportion of gold obtained in each case, we wereled up to the present method of working. From the results of agreat number of experiments, it was shown that the quantity of waterused in the grinding process was a matter of considerable importance,the success of the operation to a great extent depending upon thesand being in a damp condition only; by this means the mercurybecomes thoroughly diffused, and every grain of sand has a particleof mercury in contact with it ; consequently there is afforded abun-dant opportunity for the gold to amalgamate. On the other hand, ifsufficient water has been used to convert the mass into a semi-fluidstate, the mercury remained at the bottom of the mill, the surfaceonly being in contact with the sand; consequently the opportunityfor amalgamation was considerably lessened, and the quantity of goldextracted very much less than when working damp sand only. Asthe result of these experiments, the following process has beenadopted : The sand, after being roasted, is ground only moderatelydamp with an equal weight of mercury for three quarters of anhour, under the rollers of an ordinary Chilean mill; water is thenallowed to flow into the basin, the mill still revolving, until nearly allthe finely ground sand has been carried off in the overflow to theconcentrator; the mill is then stopped, the water drained off fromthe unground sand and mercury, again started, and recharged withfresh sand, and so on until it is necessary to clear out the amalgam-generally once a week, depending upon the richness of the mineraltreated. The finely ground sand passed into the concentrator is keptslowly stirred for a quarter of an hour, to keep the sand in suspen-sion in the water, and allow the mercury and any amalgam whichmight 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 thefirst, and is then .considered sufficiently impoverished to be allowedto run away.The quantity of roasted mineral the company treat by this process,


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- 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 costlyabout ten dollars per ton which, I think, could have beenmuch lessened had the stuff been reduced finer, and the con-centration been carried a little further, so as to have freedthe 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 iswith 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 differentparts of this State. They are mounted on glass slides formicroscopic examination, as with a common lens the pres-ence of the gold can hardly be detected ; but with a goodmicroscope, using an inch or half inch objective, it will befound that the faces of some of the crystals are, in places,most finely and beautifully gilded, and that here and thereare seen little specks or drops of gold partially imbedded inthe pyrite. The mill-man, after looking at these specimens,will not be surprised at the loss sustained in the wet stampingof 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 areobtained by carefully washing a four-pound sample in thebatea. After having in this way concentrated the gold inabout an ounce of sand and pyrites, this residue may beeither subjected to assay, or the sulphides dissolved by nitricacid, and the gold extracted by amalgamation with mercury,which is subsequently volatilized, and the gold weighed. Ineither case, calculations are made on the four-pound sample,and when the residue has been subjected to fusion, veryaccurate results are obtained.


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- 1 1 -BARREL AMALGAMATION.

During the time I was engaged in gold mining in Brazil, Istayed for some time at the St. John del Rey mine, and therewitnessed the barrel amalgamation which I described in mylast paper to the State Geological Society, and which is repro-duced here:

Their process of amalgamation is nearly perfect, but the stampingand concentration very defective, the stamps doing but little dutyonly \y^ tons per head during the 24 hours; their plan of concen-tration being principally what is called straking, consisting of anumber 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 first1 6 feet with bullocks' skins tanned with the hair on them, and inlengths of 2 feet 2 inches; below these are series of blankets orbaize cloths of the same length. The deposit of sulphurets onthe first three skins contains nearly all the gold, and amounts toabout 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 theexception of one ounce, is in a free state; the ounce of gold beingmechanically mixed with the coarser grains of pyrites.It is estimated that in stamping and straking, 10 per cent, ofthe total amount of the gold is carried off in suspension by thewater.

Their loss in amalgamation is comparatively trifling, as far as Ican gather from their numerous reports, and will average less than4 per cent.; the loss of mercury is 0.45 ounces per cubic foot of sul-phurets amalgamated. The apparatus employed for amalgamationof the sulphurets consists of wooden barrels 4 feet in length and 2feet 5 inches in diameter, having a capacity of 20 cubic feet. Thecharge of sulphurets for each barrel is one ton and a half, freefromdecomposition, and 60 pounds of mercury. There is also a sufficientamount of clean water at the same time introduced to give the slimesthe necessary degree of fluidity to enable the globules of quicksilverformed to become properly incorporated, without allowing them tobecome sufficiently mobile to admit of the settling of the mercuryand amalgam at the bottom. The barrels, when charged, are allowedto rotate from 20 to 30 hours, making 18 revolutions per minute, inaccordance 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 amalgamfrom the refuse. In this country it might be perhaps better toemploy separators the same as those used in the different panmills.

In their report of 1880 the results of their trials of


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THE COMSTOCK PAX SYSTEMWas anything but satisfactory ; indeed, in the milling for gold thatsystem appears to be too costly for low-grade ores, and not fit for therich. It is better calculated for the treatment of veinstone whichcontains in the ton from five to ten ounces of silver, and that iri asuitable mineralized condition as chlorides, etc.The attempts to grind the sulphurets when they contain upwardsof 50 per cent, of pyritic matter, and to amalgamate the mechanic-ally combined gold inclosed in the particles of pyrites, at the sametime and in the same pan, has not been attended with success fromthe earliest attempts, some of which I witnessed in Brazil in 1832,which was then made in an apparatus being a modification of theHungarian bowl. The St. John del Rey sulphurets when ready forthe barrel contain about 95 per cent, of pyritic matter, and arereduced so fine that 90 per cent, of it will pass through a sievehaving 100 holes to the linear inch.What I have tried of the California sulphurets the pyritic mattervaries from 70 per cent, to 90 per cent., and about 75 per cent, of itwill 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 latelyreceived a letter from him, wherein he tells me he is going to pub-lish another work on gold :ANALYSES OF AURIFEROUS CALIFORNIA PYRITES CONCENTRATEDFROM TAILINGS BY JOHN A. PHILLIPS.


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By careful analysis their concentrations differ but littlefrom those of some of the mines near Sonora, TuolumneCounty, CaL, the amount of arsenic varying from one to tenper cent., though in the upper part of the St. John del Reymine it did not contain so much arsenic as the followinganalysis, made by John A. Phillips in 1847, shows.

Analysis of uncrushed ores from the St. John del Reymines, made by J. Arthur Phillips, in 1847 :Silica 16.87Carbonate magnesia 12.17Carbonate lime 3.01Sulphur (iron pyrites) ^ 16.78Iron (iron pyrites) 14.65Peroxide of iron 32.84Peroxide of manganese 3.63Arsenic and gold Traces.

99.94N. 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 factof their successful treatment of such a difficult veinstone forso many years. To properly understand the magnitude ofthe work, suppose we estimate the yield of the veinstone inCalifornia, from all the mines in pyritic matter, to be, say fiveper cent, of all that is worked (which is rather high), it willhardly equal that treated daily at the St. John del Reyworks.The results of years of experience in working such a mineought to be interesting even if it were not exceedingly valu-able, as it really is ; yet there are not wanting those whoobject to any information obtained from the reports of suchas the St. John del Rey Company, on the (not very wise)grounds of the mine being worked in Brazil, and the reportsprinted and published in London ; and, may be worse thanall, that the dividends are, and have been for the last fortyyears, paid there. In the

MILLING OF CALIFORNIA GOLD QUARTZ,I would advise, for low grade rock, the stamping of it ascoarse as such a machine as the Frue, or other improvedconcentrator 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 preventwhat is termed dead stamping, and, at the same time, add


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greatly to the duty of the stamps. Screens having 12 holesto the linear inch in the bottom and 10 in the upper part,are not too coarse for low grade rock. As a stamp-headweighing 8 cwt. will then, on an average, reduce 4 tons in the24 hours,. and those of 6 cwt. about 3 tons, and any triflingloss of free gold will amply be made up by what is saved inthe sulphurets so that a Ten Stamp Mill with heads weigh-ing 8 cwt., can be made to ivork to advantage 4.0 tons of rockper day. The fineness of the stamping, however, is in partregulated by the position of the screen, that is, their hori-zontal distance from the stamp-head and the vertical height ofthe bottom of the screen above the level of the die. Forexample, 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 purposelymade lower than the back or feed part of the mortar.The Port Phillip Company, in Australia, I believe, usethem with 10 holes to the linear inch. Steel wire-cloth is thebest 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 forlow 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, ofwhich I find so large a proportion is in thin films, and which,with a rapid flow of water, would be carried away, and agreater part, of it lost, have altered my opinion on this point.

It is not generally known, but nevertheless, from numerousand very careful tests, it is proved that in fine stamping,when the speed of the stamps is above seventy-five blows perminute, that the loss of gold, when blankets or raw hides areused, is much greater than at a speed of fifty blows per min-ute; though I am not aware that any tests have been madewhen the amalgamation was done in the battery. The sys-tem of

AMALGAMATION IX THE BATTERIES,However, I have always considered a mistake and as entailsing 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 theamalgamated silver plates nearly useless. To understandthis correctly let the mill-man put two or three barrowfuls ofrock very rich in sulphurets through the stamps and thenwatch the effect on the amalgamated plate, and at the same


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- 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, withrespect to stamping, says :

Take alarge

hammer and gentlycrack a nut with it, and you have an illustration^of what astamp 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 Bodiedistrict the same as marked No. 26 one half of it poundvery fine, using a grinding action with the pestle, then washout the gold in a batea, or horn spoon, and you will find thata large proportion of the gold will float away, in spite ofevery care, even using ammonia to destroy the grease on theends of the fingers.Then take the other half, pound it very coarsely, and inwashing out the gold you will see very little float, and two orthree turns of the batea will bring all the gold into the center.

IN THE BLANKET SYSTEM,Where improved concentrators are used, after the pulp haspassed over the blankets, only two lengths of trays of aboutfour feet each, and two sets to each five stamps are required.They should be so arranged that the inclination can bealtered, say from 3 to 5, to suit the stuff being treated.The trays should be about 16 inches wide, and the fall fromthe battery box to the head tray the same as from one tray

to another, about 4 inches, with a board placed across the endthat the fall of the water or pulp will be so broken as to strikethe blanket in the tray below nearly at right angles. Theblankets should be in 3-feet lengths, and made of coarse woolwith a long nap. The double sets of trays are for the con-venience of changing and washing the blankets. The blanketwashings can be passed through a simple machine like thatdescribed 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 separatesthe gold from the gangue, but the fall, or jump, on them.Where the mill has a limited supply of water, and they donot like to go to the expense of a number of concentrators, acoarse concentrator may be made with a Tye Buddie, the


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plans and directions for the use of which will be found inPhillips' Metallurgy of Gold and Silver, page 187.The concentrations from the Tye can be passed over theFrue, one of which would then be sufficient for a large mill;though I am not prepared to say by such means they canwork 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 anangle of about 3, to which a slow lateral movement backwardand forward of orfe foot, together with a slight shake, is given,in the same direction, with a sprinkling of clean water from aperforated pipe falling on the upper part above where thepulp strikes, might be placed with advantage between theblankets and concentrators.

THE CONCENTRATIONSShould be sifted through a seive having 80 holes to the linearinch, and any particles that were not fine enough should- beground in a Chilean mill, the same as described by Mr. Latta,but without using the mercury; and afterwards charged intowooden barrels for amalgamation; but, before charging, thesulphurets should be soaked in water, to free them from alldecomposition. I feel confident that larger results will beobtained by thus treating the raw ore than if it was roasted.The great difference between a wooden surface and a metalone in amalgamation can easily be shown by washing out, say,about one dwt. of Bodie or Grass Valley gold in a batea andthen adding, with a dropping bottle, just sufficient mercuryfor it to amalgamate jvith too much or too little will lengthenthe result ; but if the proper quantity be used, by rubbing itwith the finger in the center of the bowl it will amalgamaterapidly in less than a minute. Try the same experiment withan iron pan, and you will find how much longer it takes toget the same result. I would strongly recommend any mineadventurer, before erecting any quartz mill, or adopting anyparticular process, to have some 20 or 30 tons of the rock orveinstone stamped, and to save, during that operation, a fairsample of the battery pulp from it, which should be carefullyconcentrated in a batea, or any other utensil used for washingon a small scale. The condition and quantity of the gold,


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- 19 -Nos. 15 and 16 Gold in lacotinga (micaceous iron). GongoSoco mine, Brazil. The lac^irrja veins are from a few inches tomany 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 rockwhich 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 oneof 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 ofthem, and unless very great care is taken the batea test willhardly show any gold ; notwithstanding which, on a largescale, they obtain better results from the amalgamation ofthe 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 itappears the tribute system has been introduced there withgreat success. Too much can hardly be said in favor of sucha system, as it places the hard working and intelligent mineron a much more respectable and independent footing; andthough he in a measure shares the risks, but only so far ashis judgment guides him, he gets the benefit of any discoveryhe may make. It also encourages him to study the peculiari-ties of the lode and inclosing rocks ; besides which, by thatsystem, all are jointly interested in the welfare of the mine.Many of the mines now idle in this State could be workedprofitably 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


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with the tributers to drive the levels in the ground let to them, thecompany assisting them with driving timber and rails, and makingan allowance per fathom until the yield reaches 6 dwts. per ton,when no further assistance is given; the company receiving half thegold 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' accountfor the year was 48,184 tons. The average yield of the entirequantity raised was 5 dwts. 5^ grains per ton (say 5).Total receipts 82,364 14s 7clExpenditure 26,310 10s 7dLeaving a profit of 0,054 4s OdIn conclusion, so thoroughly am I convinced of the great

benefits that would result to this State by a more generalintroduction of the tribute system in an extended form, bothto the placer as well as vein mining, that I wish particularlyto call your attention to it, so that, through the influence ofthe Bureau, the subject may be brought in a proper lightbefore the owners of mines or claims. A fair tribute willsecure the muscle of the working miner, who, in too manycases, understands better than the Superintendent (generallya man of business) how to conduct trials for ore, and after-ward to develop them. The muscle of the skilled miner is inevery respect better than foreign capital.

There is no need of the hard-working miner to leave thishealthy climate in search of employment, if those who ownmines that are now idle would let the fact be known throughthe press, and at the same time offer a fair tribute for workingthem.


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14 DAY USERETURN TO DESK FROM WHICH BORROWEDLOAN DEPT.This book is due on the last date stamped below, oron the date to which renewed.Renewed books are subject to immediate recall.

AMar'frSPH


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Attwood, M. Milling of Gold Quartz, 1882

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