Volume 39 (1879) (446 pages)

MINING AND SCIENTIFIC PRESS. [July 5, 1879. 5 {GorresPonDeENce. of corrospondents.—Eps We admit, dorsed, opini Shasta County. Epirors Press:—At Mad Ox, seven miles above Whisky Town, we find the quartz mill owned by Messrs. Grotafend, Brickford & Co., in fine running order, with its double turbine water wheel, from A. Myers, San Francisco. The mill is running day and night, the partics are confident of a good thing in their mine, which is well located with a large body of finelooking quartz now in sight. The extension of tbis mine known as the Peckham mine, now owned by A, Saulan, Warfield, Scott & Co., is turning out a large amount of good quartz, worked by an arastra, pays from $100 to $140 per ton, ledge from 3 to 54 feet in thickness. On Mad Mule Mr. Banghart is working his seam diggings very quietly, but with satisfactory results. Since 1866 he has bis new tunnel in 500 feet, and is within a few feet of his pay chimuey, or seam, which is very rich. Ex-Sheriff Jackson is working the extension with good prospects. The diggings have heen very rich in the gulches in tbis vicinity in past years. , : The Bell & Knox mine on Grizzly gulch, in same district, bas yielded a large amount of gold during the past two years. The mining interests around French Gulch are very encouraging. Messrs. John, Souter, Simes & Co. are getting the old Washington mill and mine in running order again, as they have found new bodies of ore. The quartz in this district is gold bearing. F. McConnell and H. Dorr have a fine prospect higher up the mountain, their ledge is hetween slate and porphyry, rock averaging from $40 to $70 per ton, worked by an arastraright at tbe mine. V. Kern is also running an arastra on tbe north fork of the creek with equally good results. Passing over the mountain at an altitude of 4,100 feet (into Trinity county), we find Deadwood gulch, on which five arastras are now running—George Keine, two; G. F. Deiner, two; Waver Sehastian, one. Mr. Willey and Mr. Davis are also working very rich ore from their mines. Ores in this district run from $70 to $120 per ton, and some has run even higber than that. There is no doubt but this will prove a fine district, it is well located, formation elate and porphyry, the same as French Gulch district, and the gold of good quality. B. Chrome Mines in San Luis Obispo. Epirors Press:—On the afternoon of Saturday last I had tbe pleasure of visiting with an acquaintance the ‘‘chrome” mines among the hills about eight miles distant. For about five miles the road leads through a picturesque valley, watered by a perennial stream which is fringed with a rich growth of grass and sycamore trees. In passing through we noticed evidences that more than one picnic party bad practically appreciated the inviting ebade. On leaving this valley we ascended the ‘‘grade,” which is a road cut along the side of the mountain eomewhat spirally, and is of just sufficient width for one team only; though there are ‘‘bays” here and tbere for tbe convenience of teams passing one anotber. Where the “grade” was steepest and narrowest, and in every uncomfortable way most suggestive, tbe hill bore nothing to which in an emergency one could cling but wild oats; above this there was a tbick chaparral growtb interpersed with pines and cedars; here too were some large manzanita busbes whose stems were 10 or 11 inches in diameter, Having attained tbe bighest point, and seen four Chinamen just beginning a new miue, we returned, and ou the way halted for water at the house of Mr. Louis G, Flores, of San Luis Obispo, who owns the mines and a large area ofland. We were fortunate enough to fiud him at home, and he at once offered us his hospitalities. Having refresbed ourselves and tbe horses, Mr. Wlores conducted us _ to his most productive mine, Here we found men at work in a tunnel running abont 200 feet into a hill. Mr. Flores described to us tbe cbaracteristica of the chrome ore, and pointed out the dips and leads of tbe various veins, and sbowed ns one vein that bad increased in breadth as the minere followed it, until it developed into a huge eubterraneous mound of pure cbrome, The ore ie eorted, screened, and then hauled to the depot of the S. L. O. andS. M. V. RB. R., whence it is taken hy rail to Port Harford, thence to Baltimore by way of Sau Francisco, The only factory in the country, for using thie chrome ore at present, is at Baltimore. The price paid at the depot here ie $8 per ton, which, in the opinion of those qualified to judge, is not a sufficient compeneation, We returned home after an enjoyahle trip. San Luie Obiepo, Cal., June 16th. Great Western Quicksilver Mine. Eprrors Press:—Among the first, if not the first mine now being worked for mercury, is the Great Western, near Middletown, in Lake county, which bas for several years heen under able management of the experienced mining engineer, Andrew Rocca, now running a force of 250 men, Tbe mine discharges the ores hy tunnel and trains of borse cars rigbt at the furnaces and assorting sheds, Tbe tunnel for main discharge is now in a distance of half a mile, There is also a tunnel discharging througb the mountain on the west side to anotber furnace there. The principal extracting of quicksilver is done hy one fine-ore furnace ef the capacity of 13 tons in 24 hours; and three coarse-ore furnaces, each of capacity of 35 tons in 24 hours. Of the coarse-ore furnaces, two are Greene’s excellent furnaces; one of Coult’s—patented in 1867 by Josepb Coult, then of Pope Valley, but now in Texas. This furnace gives the best, easiest and cheapest results; does not cost one-fourth as mucb as tbe others —$5,000 will put up two of them witb condensers. The ine-ore condenser uses,a Livermore condenser. Uses Hercules Giant powder as the best and safest—have tested all kinds—using ahout $600 worth per montb; average about 160 shots or blasts each six hours. Mr, Rocca is a progressive man and has introduced many new, original and practical ideas in his various machines. His glass-roofed condensers are proving a perfect success. The flow of metal from tbe furnaces has not ceased for the last three years, yielding 500 to 600 flasks per month, or about 7,000 to 8,000 flasks per annum, which is sent hy freight teams to Cal. istoga depot at $6 per ton over Lawley’s toll road. Men work 10-hour shifte between 7 a. mu. and 6 p, m., and from 7 P. um. to 6 A. M. The Sulphur Bank and Oat Hill mines are doing well, hut not working up to full capacity. The latter mine is considered an excellent mine and under very successful management. Dr. Baker, below the lake six miles, is doing well for the amount of capital now at hie command, He claims some successful improvements in furnace and condensers, and deserves ample success for his great perseverance where capital was lacking. B. W. C. Middletown, June 9th. The Telluride Ores of Gold.—No. 4. (Thesis by Russeun L. Dunn, College of Mines, University of California.] Special Processes. Smelting with copper oree usually more or less auriferous and argentiferous to a copper matte. Tbie is the process employed at the Boston and Colorado works at present. When first introduced the Ziervogel process was used to part the gold and silver from tbe copper ; this, it is said on account of the expensiveness of the chemicals employed, was abandoned. Since then a secret metbod, invented by Prof Pearce, bas been used, and is claimed to give better and cheaper results than any other yet applied, Tbe Boston and Colorado works have treated the greater portion of tbe telluride ores of Colorado. Smelting with auriferous iron pyrites to an iron matte. Tbie process, so far as I bave information, has never been used with telluride ores, though recommended, Smelting witb lead ores to base bullion is often used and eeems to be fairly successful. Very rich ores are not usually treated by this method. Tbe process is in use in Boyd’s smelting works ‘at Boulder City, Colorado, on oree too poor in gold and silver to be smelted in a lead hath. The base bullion can be refined and parted by the usual methods. As compared with the Copper Matte process described ahove, it is said not to give as high a percentage of return. Smelting in a lead bath. Into a test of melted lead very finely pulverized ore is fed in quantities of from 10 Ibs. to 15 lbs. at a time. The slag is skimmed off from time to time as it accumulates in excess ; as soon as the lead is sufficiently enriched it is removed and a fresh charge of lead introduced, The relning and parting of the enriched lead are done in the usual way. Tbe same lead can be used over and over again, the unrecoverable loss being small, This process isin use in Boyd’s works at Boulder city, Colorado. _ Mr, Boyd has patented what he considers an improvement hy which the ore as it ie fed into the test is forced beneath the surface of the melted lead and retained there until the tellurium minerals are decomposed and the tellurium driven off. ‘Theoretically the principle seems good, how it works practically Iam unable to say as accounts vary, Rich oree are sometimes smelted in cruciblee with litharge and reduciug fluxes. A high per. centage of metal is of course returned, but at a proportionately bigher expenditure, All of the crucible, and the cupellation lead bath procese are quite costly, and with the exception of tbe latter only euitable ae experimental processee on a small ecale. None of them, except under favorable circumetances, can treat other than high gradee of ore. The matte processee are tbe beet on a large ecale. For them and for furnace pro in too fine. At tbe Boston and Colorado works at Denver, the ore ie crusbed by steel rolls so as to pass through sieves of 10 holes to the running inch. For cupel and crucible processes tbe ore must be finely pnlverized. Tbe table will show where smelting is and can be applied, Amalgamation. Very little need be said about tbie branch of the metallurgy, as telluride ores will not amalgamate. Amalgamation ie decidedly the best treatment for gold ores where it can be applied directly to metallic gold in a finely divided condition, No other metbod will yield so high a percentage of the gold in tbe ore at so lowa cost. But mercury will not decompose tellurides so as to amalgamate tbe gold and silver in tbem. Iam informed tbat the mercury cuts up and blackens, acting very much as with base metal cblorides and sulphates. In attempting to mill some extremely rich ore from the Stanislaus mine in California, it was found tbat only from 5% to 10% of the gold was saved; attempts since made in Colorado bave succeeded no better. Where there is much free gold and few tellurets and sulpburets in the rock, it is possihle to crush tbe ore wet, run it through the amalgamation plent, and thence to concentrators which will save tbe tellurets and sulpburets and concentrate tbem to second class ore. I know of no inetance in which tbis process is employed at the present time, and frora general principles it is only to bo recommeuded in the case i above, where it is obviously more economical, Roaeting. The roasting of telluride ores is the most interesting as well as the moet important point in connection with their metallurgy. It is true that roasting is now practically abandoned on account of the large loss of metal by volatilization, but if some economical mode were discovered by which the ore could be perfectly roasted without loss, it would become used to the almost entire exclusion of smelting. Roasting is the only economical way of preparing mineralized gold ores for amalgamation, All kinds of fur. naces have been tried on these ores, reverberatory, Bruckner’s cylinders, and in fact almost every roasting device which tbe ingenuity of the metallurgist could invent,’and thue far, none of them, judging from the length of time they were used, are more than partially euccessful at the best. The principal reason why roasting has not been successful ie the volatility of gold, and in a less degree silver, with tellurium and tellurous acid, Mr. Kustel, who in 1865 said that the ores could be roasted in a reverberatory furnace euccessfully, made eome experiments on ores from Colorado a few yearsago. He roasted them himself in tbe sulphuret roasting furnace connected with the cblorination plant at Grass Valley, paying the most careful attention to the rate of roasting and the regulation of the draft, and the best result he was able to obtain showed a loss by volatilization of 97%. This peculiar volatilization of gold is one of the unsolved problems of chemistry. It is said to occur in roasting sulphurets, but some careful experimente by Mr. Kustel convinced him that in tbis case the loss was mecbanical and caused by a too rapid roasting. Arsenic and antimony seem to have more or less of the same power (doubtful) of causing gold to vaporize. It is, bowever, most marked with tellurium. Whetber the gold vaporizes as gold or volatilizes as a telluride of gold has not yet been discovered, but the latter eupposition would seem to be the most probable, although it may be both. Gold is slightly volatile at high temperatures. A rather curious instance of this property occurred in the Boston and Colorado works at Black Hawk, Colorado, eeveral yeare ago. In breaking up a hearth from a reverberatory furnace used for roasting iron matte, flakes and wires of pure bright gold were found in the quartz bed at some distance below the eurface ofthe same. How the gold got there from ahove is a mystery even under the supposition (most probable) of vaporization and condensation. It is necessary that telluride ores should be crushed dry and very fine for thorough roasting. The usual plant for roasting and the method of carrying on the process are the same as are used for roasting ordinary auriferone iron pyrites, only considerahle more attention must be given to the manipulation, as the roasting is much more delicate. As the ordinary roasting furnace is well known, it is not necessary for me to give any description of it. Willard’e furnace is peculiar both in construction and manner of working. Heat is applied to the exterior by a fire underneath, and the roasting goes on inside supported by sawdust or some other finely divided oarbonaceoue matter which is mixed with the ore, A hlast is used to supply air to tbe inside of tbe furnace. The roasted ore can be treated in three ways, viz., dry amalgamation, wet amalgamation and chlorination. By tbe lirst more or less gold and floured amalgam are unavoidably lost, The fineness of division of tbe gold and eilver ie eo extreme that the particles are liahle to remain euspended in water and pass off with the elimes in wet amalgamation. By chlorination the silver ie of course loet unlees anotber process be subsequently employed to save it, Roasting proceeses as a rule can treat equally well all gradee of ore, hut tbe richer the ore the more careful ehould be the manipulation, Chemical Proceeses, Etc. Under tbie head I include all of the eo-called general tbe telluride ores sbould not be crushed wet pro which bave or can be applied in reducing telluride ores, I can learn of no in“to it by steel springs. etance in which any of tbem bave been applied on alarge scale as practical processes. Acids bave been used to dissolve out tbe tellurium, after which it was easy to extract the metal. Such processes are, bowever, far too costly for any but the ricbest ore. Mr. Stewart made some experiments, or rather teets, with bis modification of the Hunt and Douglas copper reduction process, at Georgetown, Col. Tbey were on a small scale, hut he claims euccessful. His process will treat ore of any grade without previous roasting, Concentration. It is found unprofitable to work low grades of tbese ores by smelting raw, and it is therefore necessary to concentrate first. By concentrating it hae been made possible to reduce all rock coming from the mine with as low a value as $15 or $20 per ton. Tbe thorough concentration of telluride ores ie somewhat difficult. Owing to the complete dissemination of the small particles of mineral the ore must be crushed very fine, and then of course more or less will be lost in tbe tailings and slimes from the macbines. Also in crushing fine, tbe brittle mineral is powdered, while the gangue remaine in comparatively large particles—that is, the gangue and mineral are not crusbed equally, thusmaking a preliminary sizing of tbe crushed ore necessary, with the use of the usual machines. It can be readily seen tbat the German metbods, sieving and jigging, are not applicable to sucb fine ore. The ordinary modes of concentration employed in California and on tbe Pacific coast for eulphurete are mucb better. Buddles, cradles and blankethoxes all do good work, though by no means as perfect as can be desired. A machine has been in use in the last few years in the Telluride dietrict of Colorado, which seems to do better work than any of the others. It is called tbe Frue Vanning machine or ore concentrator. It consists of an endless rubber belt moving upward by tbe revolving of the rollers on which it is stretched, A rapid lateral vibration is given Tbe ore and water are fed continuously on the surface, and the tailings discharged at the foot, while the concentratione are wasbed off in a box filled with water, tbrough which the belt travels. The macbine ie perfectly automatic in action, hand labor only being required from time to time to remove tbe concentrations, As regarde the absolute efficiency of these machines (i. ¢., the percentage of the mineral in a given grade of ore they will eave), accounts . differ, The last described would seem to be tke best, as the otbers bave been discarded almost entirely for it. Even it, however, would not seem to be all tbat is desired, from the fact that it will not treat economically as low grades oftellurides as of other gold ores. Very little more remains to be said of the . beneficiation, except to note that there is still . room for improvement.*: It bas been noticed by . smeltere tbat certain fluxes, more particularly ; limestone, seem to reduce the volatilization of f the metal, and it is possible that some substance . may yet be found which will bave the same in. fluence in the roasting furnace. In wet pro. cesses we may find tbe true metbod of working ; these ores, but roasting, with amalgamation or . chlorination are at present the most available ; for improvement. [Concluded ] The Treatment of Auriferous and Ar gentiferous Pyrites. Tbe trouble experienced in dealing with # sulphurets” is so well known that it will be . unnecessary to say that every new method! which will serve to reduce the cost and tbelosses of extracting gold, silver and copper from ores running high in pyrites, deserves attention, A recent modification of known methods ie that ! proposed by Mr, W, A. Dixon, who has made a: series of experiments to test its value, so far as! laboratory work can accomplish that object, He: roasts the ore on a matte smelted from tbe ore: in a muffle roasting furnace, and utilizes tbe eulpburous acid formed for the manufacture of a dilute sulphuric acid, in suitable combination : chambere and condensation towere. Any arsenious acid formed is deposited in a flue previous to the gases entering the combination chamber, So far the process does notin anys . way differ from existing methods. Before beihg, discharged from the muffle furnace the roasted . I ore is mixed with a proper amount of coal dust or any other carhonaceous matter, and then it is transferred to a reverberatory fnrnace, in which a reducing flame is maintained. Thie reduces the oxides, formed in the preliminary] roasting, to metals. The material is then car. ried into vats, where a large portion of the iron) M ie extracted by means of the acid solution from the towers in tbe shape of asulpbate. The re. sidue, which contains free gold and silver, ig amalgamated, If copper is preeent in coneiderable quantities, the process is somewhat modi. fied. The ore, after baving been roasted in the muffle furnace, ie lixiviated with an acid eolu. fs tion of copper, and then with water. Tbe re. sidue ie mixed with carhon and treated further in the manner deecribed. Tbe procese ir claimed to poseees the advantage of suffering less from poor roasting and of being conducted at a low temperature, witb ite attendant de. Kini creaee of coet of fuel, of plant and of lose by ty volatilization, There ie none of the expense conneoted witb chlorinizing roasting nor any} outlay for precipitants,—Jron Age. Bh

MINING AND SCIENTIFIC PRESS. [July 5, 1879. 5 {GorresPonDeENce. of corrospondents.—Eps We admit, dorsed, opini Shasta County. Epirors Press:—At Mad Ox, seven miles above Whisky Town, we find the quartz mill owned by Messrs. Grotafend, Brickford & Co., in fine running order, with its double turbine water wheel, from A. Myers, San Francisco. The mill is running day and night, the partics are confident of a good thing in their mine, which is well located with a large body of finelooking quartz now in sight. The extension of tbis mine known as the Peckham mine, now owned by A, Saulan, Warfield, Scott & Co., is turning out a large amount of good quartz, worked by an arastra, pays from $100 to $140 per ton, ledge from 3 to 54 feet in thickness. On Mad Mule Mr. Banghart is working his seam diggings very quietly, but with satisfactory results. Since 1866 he has bis new tunnel in 500 feet, and is within a few feet of his pay chimuey, or seam, which is very rich. Ex-Sheriff Jackson is working the extension with good prospects. The diggings have heen very rich in the gulches in tbis vicinity in past years. , : The Bell & Knox mine on Grizzly gulch, in same district, bas yielded a large amount of gold during the past two years. The mining interests around French Gulch are very encouraging. Messrs. John, Souter, Simes & Co. are getting the old Washington mill and mine in running order again, as they have found new bodies of ore. The quartz in this district is gold bearing. F. McConnell and H. Dorr have a fine prospect higher up the mountain, their ledge is hetween slate and porphyry, rock averaging from $40 to $70 per ton, worked by an arastraright at tbe mine. V. Kern is also running an arastra on tbe north fork of the creek with equally good results. Passing over the mountain at an altitude of 4,100 feet (into Trinity county), we find Deadwood gulch, on which five arastras are now running—George Keine, two; G. F. Deiner, two; Waver Sehastian, one. Mr. Willey and Mr. Davis are also working very rich ore from their mines. Ores in this district run from $70 to $120 per ton, and some has run even higber than that. There is no doubt but this will prove a fine district, it is well located, formation elate and porphyry, the same as French Gulch district, and the gold of good quality. B. Chrome Mines in San Luis Obispo. Epirors Press:—On the afternoon of Saturday last I had tbe pleasure of visiting with an acquaintance the ‘‘chrome” mines among the hills about eight miles distant. For about five miles the road leads through a picturesque valley, watered by a perennial stream which is fringed with a rich growth of grass and sycamore trees. In passing through we noticed evidences that more than one picnic party bad practically appreciated the inviting ebade. On leaving this valley we ascended the ‘‘grade,” which is a road cut along the side of the mountain eomewhat spirally, and is of just sufficient width for one team only; though there are ‘‘bays” here and tbere for tbe convenience of teams passing one anotber. Where the “grade” was steepest and narrowest, and in every uncomfortable way most suggestive, tbe hill bore nothing to which in an emergency one could cling but wild oats; above this there was a tbick chaparral growtb interpersed with pines and cedars; here too were some large manzanita busbes whose stems were 10 or 11 inches in diameter, Having attained tbe bighest point, and seen four Chinamen just beginning a new miue, we returned, and ou the way halted for water at the house of Mr. Louis G, Flores, of San Luis Obispo, who owns the mines and a large area ofland. We were fortunate enough to fiud him at home, and he at once offered us his hospitalities. Having refresbed ourselves and tbe horses, Mr. Wlores conducted us _ to his most productive mine, Here we found men at work in a tunnel running abont 200 feet into a hill. Mr. Flores described to us tbe cbaracteristica of the chrome ore, and pointed out the dips and leads of tbe various veins, and sbowed ns one vein that bad increased in breadth as the minere followed it, until it developed into a huge eubterraneous mound of pure cbrome, The ore ie eorted, screened, and then hauled to the depot of the S. L. O. andS. M. V. RB. R., whence it is taken hy rail to Port Harford, thence to Baltimore by way of Sau Francisco, The only factory in the country, for using thie chrome ore at present, is at Baltimore. The price paid at the depot here ie $8 per ton, which, in the opinion of those qualified to judge, is not a sufficient compeneation, We returned home after an enjoyahle trip. San Luie Obiepo, Cal., June 16th. Great Western Quicksilver Mine. Eprrors Press:—Among the first, if not the first mine now being worked for mercury, is the Great Western, near Middletown, in Lake county, which bas for several years heen under able management of the experienced mining engineer, Andrew Rocca, now running a force of 250 men, Tbe mine discharges the ores hy tunnel and trains of borse cars rigbt at the furnaces and assorting sheds, Tbe tunnel for main discharge is now in a distance of half a mile, There is also a tunnel discharging througb the mountain on the west side to anotber furnace there. The principal extracting of quicksilver is done hy one fine-ore furnace ef the capacity of 13 tons in 24 hours; and three coarse-ore furnaces, each of capacity of 35 tons in 24 hours. Of the coarse-ore furnaces, two are Greene’s excellent furnaces; one of Coult’s—patented in 1867 by Josepb Coult, then of Pope Valley, but now in Texas. This furnace gives the best, easiest and cheapest results; does not cost one-fourth as mucb as tbe others —$5,000 will put up two of them witb condensers. The ine-ore condenser uses,a Livermore condenser. Uses Hercules Giant powder as the best and safest—have tested all kinds—using ahout $600 worth per montb; average about 160 shots or blasts each six hours. Mr, Rocca is a progressive man and has introduced many new, original and practical ideas in his various machines. His glass-roofed condensers are proving a perfect success. The flow of metal from tbe furnaces has not ceased for the last three years, yielding 500 to 600 flasks per month, or about 7,000 to 8,000 flasks per annum, which is sent hy freight teams to Cal. istoga depot at $6 per ton over Lawley’s toll road. Men work 10-hour shifte between 7 a. mu. and 6 p, m., and from 7 P. um. to 6 A. M. The Sulphur Bank and Oat Hill mines are doing well, hut not working up to full capacity. The latter mine is considered an excellent mine and under very successful management. Dr. Baker, below the lake six miles, is doing well for the amount of capital now at hie command, He claims some successful improvements in furnace and condensers, and deserves ample success for his great perseverance where capital was lacking. B. W. C. Middletown, June 9th. The Telluride Ores of Gold.—No. 4. (Thesis by Russeun L. Dunn, College of Mines, University of California.] Special Processes. Smelting with copper oree usually more or less auriferous and argentiferous to a copper matte. Tbie is the process employed at the Boston and Colorado works at present. When first introduced the Ziervogel process was used to part the gold and silver from tbe copper ; this, it is said on account of the expensiveness of the chemicals employed, was abandoned. Since then a secret metbod, invented by Prof Pearce, bas been used, and is claimed to give better and cheaper results than any other yet applied, Tbe Boston and Colorado works have treated the greater portion of tbe telluride ores of Colorado. Smelting with auriferous iron pyrites to an iron matte. Tbie process, so far as I bave information, has never been used with telluride ores, though recommended, Smelting witb lead ores to base bullion is often used and eeems to be fairly successful. Very rich ores are not usually treated by this method. Tbe process is in use in Boyd’s smelting works ‘at Boulder City, Colorado, on oree too poor in gold and silver to be smelted in a lead hath. The base bullion can be refined and parted by the usual methods. As compared with the Copper Matte process described ahove, it is said not to give as high a percentage of return. Smelting in a lead bath. Into a test of melted lead very finely pulverized ore is fed in quantities of from 10 Ibs. to 15 lbs. at a time. The slag is skimmed off from time to time as it accumulates in excess ; as soon as the lead is sufficiently enriched it is removed and a fresh charge of lead introduced, The relning and parting of the enriched lead are done in the usual way. Tbe same lead can be used over and over again, the unrecoverable loss being small, This process isin use in Boyd’s works at Boulder city, Colorado. _ Mr, Boyd has patented what he considers an improvement hy which the ore as it ie fed into the test is forced beneath the surface of the melted lead and retained there until the tellurium minerals are decomposed and the tellurium driven off. ‘Theoretically the principle seems good, how it works practically Iam unable to say as accounts vary, Rich oree are sometimes smelted in cruciblee with litharge and reduciug fluxes. A high per. centage of metal is of course returned, but at a proportionately bigher expenditure, All of the crucible, and the cupellation lead bath procese are quite costly, and with the exception of tbe latter only euitable ae experimental processee on a small ecale. None of them, except under favorable circumetances, can treat other than high gradee of ore. The matte processee are tbe beet on a large ecale. For them and for furnace pro in too fine. At tbe Boston and Colorado works at Denver, the ore ie crusbed by steel rolls so as to pass through sieves of 10 holes to the running inch. For cupel and crucible processes tbe ore must be finely pnlverized. Tbe table will show where smelting is and can be applied, Amalgamation. Very little need be said about tbie branch of the metallurgy, as telluride ores will not amalgamate. Amalgamation ie decidedly the best treatment for gold ores where it can be applied

directly to metallic gold in a finely divided condition, No other metbod will yield so high a percentage of the gold in tbe ore at so lowa cost. But mercury will not decompose tellurides so as to amalgamate tbe gold and silver in tbem. Iam informed tbat the mercury cuts up and blackens, acting very much as with base metal cblorides and sulphates. In attempting to mill some extremely rich ore from the Stanislaus mine in California, it was found tbat only from 5% to 10% of the gold was saved; attempts since made in Colorado bave succeeded no better. Where there is much free gold and few tellurets and sulpburets in the rock, it is possihle to crush tbe ore wet, run it through the amalgamation plent, and thence to concentrators which will save tbe tellurets and sulpburets and concentrate tbem to second class ore. I know of no inetance in which tbis process is employed at the present time, and frora general principles it is only to bo recommeuded in the case i above, where it is obviously more economical, Roaeting. The roasting of telluride ores is the most interesting as well as the moet important point in connection with their metallurgy. It is true that roasting is now practically abandoned on account of the large loss of metal by volatilization, but if some economical mode were discovered by which the ore could be perfectly roasted without loss, it would become used to the almost entire exclusion of smelting. Roasting is the only economical way of preparing mineralized gold ores for amalgamation, All kinds of fur. naces have been tried on these ores, reverberatory, Bruckner’s cylinders, and in fact almost every roasting device which tbe ingenuity of the metallurgist could invent,’and thue far, none of them, judging from the length of time they were used, are more than partially euccessful at the best. The principal reason why roasting has not been successful ie the volatility of gold, and in a less degree silver, with tellurium and tellurous acid, Mr. Kustel, who in 1865 said that the ores could be roasted in a reverberatory furnace euccessfully, made eome experiments on ores from Colorado a few yearsago. He roasted them himself in tbe sulphuret roasting furnace connected with the cblorination plant at Grass Valley, paying the most careful attention to the rate of roasting and the regulation of the draft, and the best result he was able to obtain showed a loss by volatilization of 97%. This peculiar volatilization of gold is one of the unsolved problems of chemistry. It is said to occur in roasting sulphurets, but some careful experimente by Mr. Kustel convinced him that in tbis case the loss was mecbanical and caused by a too rapid roasting. Arsenic and antimony seem to have more or less of the same power (doubtful) of causing gold to vaporize. It is, bowever, most marked with tellurium. Whetber the gold vaporizes as gold or volatilizes as a telluride of gold has not yet been discovered, but the latter eupposition would seem to be the most probable, although it may be both. Gold is slightly volatile at high temperatures. A rather curious instance of this property occurred in the Boston and Colorado works at Black Hawk, Colorado, eeveral yeare ago. In breaking up a hearth from a reverberatory furnace used for roasting iron matte, flakes and wires of pure bright gold were found in the quartz bed at some distance below the eurface ofthe same. How the gold got there from ahove is a mystery even under the supposition (most probable) of vaporization and condensation. It is necessary that telluride ores should be crushed dry and very fine for thorough roasting. The usual plant for roasting and the method of carrying on the process are the same as are used for roasting ordinary auriferone iron pyrites, only considerahle more attention must be given to the manipulation, as the roasting is much more delicate. As the ordinary roasting furnace is well known, it is not necessary for me to give any description of it. Willard’e furnace is peculiar both in construction and manner of working. Heat is applied to the exterior by a fire underneath, and the roasting goes on inside supported by sawdust or some other finely divided oarbonaceoue matter which is mixed with the ore, A hlast is used to supply air to tbe inside of tbe furnace. The roasted ore can be treated in three ways, viz., dry amalgamation, wet amalgamation and chlorination. By tbe lirst more or less gold and floured amalgam are unavoidably lost, The fineness of division of tbe gold and eilver ie eo extreme that the particles are liahle to remain euspended in water and pass off with the elimes in wet amalgamation. By chlorination the silver ie of course loet unlees anotber process be subsequently employed to save it, Roasting proceeses as a rule can treat equally well all gradee of ore, hut tbe richer the ore the more careful ehould be the manipulation, Chemical Proceeses, Etc. Under tbie head I include all of the eo-called general tbe telluride ores sbould not be crushed wet pro which bave or can be applied in reducing telluride ores, I can learn of no in“to it by steel springs. etance in which any of tbem bave been applied on alarge scale as practical processes. Acids bave been used to dissolve out tbe tellurium, after which it was easy to extract the metal. Such processes are, bowever, far too costly for any but the ricbest ore. Mr. Stewart made some experiments, or rather teets, with bis modification of the Hunt and Douglas copper reduction process, at Georgetown, Col. Tbey were on a small scale, hut he claims euccessful. His process will treat ore of any grade without previous roasting, Concentration. It is found unprofitable to work low grades of tbese ores by smelting raw, and it is therefore necessary to concentrate first. By concentrating it hae been made possible to reduce all rock coming from the mine with as low a value as $15 or $20 per ton. Tbe thorough concentration of telluride ores ie somewhat difficult. Owing to the complete dissemination of the small particles of mineral the ore must be crushed very fine, and then of course more or less will be lost in tbe tailings and slimes from the macbines. Also in crushing fine, tbe brittle mineral is powdered, while the gangue remaine in comparatively large particles—that is, the gangue and mineral are not crusbed equally, thusmaking a preliminary sizing of tbe crushed ore necessary, with the use of the usual machines. It can be readily seen tbat the German metbods, sieving and jigging, are not applicable to sucb fine ore. The ordinary modes of concentration employed in California and on tbe Pacific coast for eulphurete are mucb better. Buddles, cradles and blankethoxes all do good work, though by no means as perfect as can be desired. A machine has been in use in the last few years in the Telluride dietrict of Colorado, which seems to do better work than any of the others. It is called tbe Frue Vanning machine or ore concentrator. It consists of an endless rubber belt moving upward by tbe revolving of the rollers on which it is stretched, A rapid lateral vibration is given Tbe ore and water are fed continuously on the surface, and the tailings discharged at the foot, while the concentratione are wasbed off in a box filled with water, tbrough which the belt travels. The macbine ie perfectly automatic in action, hand labor only being required from time to time to remove tbe concentrations, As regarde the absolute efficiency of these machines (i. ¢., the percentage of the mineral in a given grade of ore they will eave), accounts . differ, The last described would seem to be tke best, as the otbers bave been discarded almost entirely for it. Even it, however, would not seem to be all tbat is desired, from the fact that it will not treat economically as low grades oftellurides as of other gold ores. Very little more remains to be said of the . beneficiation, except to note that there is still . room for improvement.*: It bas been noticed by . smeltere tbat certain fluxes, more particularly ; limestone, seem to reduce the volatilization of f the metal, and it is possible that some substance . may yet be found which will bave the same in. fluence in the roasting furnace. In wet pro. cesses we may find tbe true metbod of working ; these ores, but roasting, with amalgamation or . chlorination are at present the most available ; for improvement. [Concluded ] The Treatment of Auriferous and Ar gentiferous Pyrites. Tbe trouble experienced in dealing with # sulphurets” is so well known that it will be . unnecessary to say that every new method! which will serve to reduce the cost and tbelosses of extracting gold, silver and copper from ores running high in pyrites, deserves attention, A recent modification of known methods ie that ! proposed by Mr, W, A. Dixon, who has made a: series of experiments to test its value, so far as! laboratory work can accomplish that object, He: roasts the ore on a matte smelted from tbe ore: in a muffle roasting furnace, and utilizes tbe eulpburous acid formed for the manufacture of a dilute sulphuric acid, in suitable combination : chambere and condensation towere. Any arsenious acid formed is deposited in a flue previous to the gases entering the combination chamber, So far the process does notin anys . way differ from existing methods. Before beihg, discharged from the muffle furnace the roasted . I ore is mixed with a proper amount of coal dust or any other carhonaceous matter, and then it is transferred to a reverberatory fnrnace, in which a reducing flame is maintained. Thie reduces the oxides, formed in the preliminary] roasting, to metals. The material is then car. ried into vats, where a large portion of the iron) M ie extracted by means of the acid solution from the towers in tbe shape of asulpbate. The re. sidue, which contains free gold and silver, ig amalgamated, If copper is preeent in coneiderable quantities, the process is somewhat modi. fied. The ore, after baving been roasted in the muffle furnace, ie lixiviated with an acid eolu. fs tion of copper, and then with water. Tbe re. sidue ie mixed with carhon and treated further in the manner deecribed. Tbe procese ir claimed to poseees the advantage of suffering less from poor roasting and of being conducted at a low temperature, witb ite attendant de. Kini creaee of coet of fuel, of plant and of lose by ty volatilization, There ie none of the expense conneoted witb chlorinizing roasting nor any} outlay for precipitants,—Jron Age. Bh