Show milling practice at the consolidated mercur mer cur WRITTEN FOR THE MINING REVIEW BY LEROY A PALMER I 1 I 1 from the first day when the management of the old mercur mine realized that I 1 its battery plates would not successfully amala amalgamate amate its ores to the present the history of this interesting company and its successor the consolidated mercur has been a record of struggles against conditions which have been met with a bulldog determination and overcome only to find a tion of payments for about three years it bids fair to emerge from its last period of hard luck and ana r resume i e its onward march few people even among shosoo to whom con mercur is almost a household word know a tenth of the story the opening of the property as a quicksilver quick silver producer the shutdown and the discovery of the little streak streak of gold the sale as a gold mine and aa v 4 1 W mown T V 11 at aa photo b harry Shit ler the consolidated mercur mill mercur utah new difficulty ahead but in spite of all adversity diversity dver sity this grand old mine has always I 1 ahead under a management not daunted auntee by natures obstacles and daring to ake moves along unbroken trails whenever there here was a good prospect of such moves longing it to the desired goal in its periods of prosperity it has paid out dividends P f about and now after a cessa the attempts to mill the ore by the systems then in vogue the tests by the cyanide process then a new thing and the construction of the first mill for commercial treatment of ore by cyaniding cyan iding in america and one of the first in the world then with the new plant built it refused to work a as s the tests had shown that it should and there came another shutdown shut down the difficulty one of c r I 1 arg w was a s to c a fe d 16 I 1 ng S ro oj can P gain until the base ore was struck again the story of tests and experiments and the problem was solved this time by roasting and another reign of prosperity inaugurated until the ore values went down to the point that working could not be conducted at a profit obviously the management could not put more gold into the ore so the only alternative was to take more out of it that is to make mahe a higher percentage of extraction an and d it was just about three years ago that work toward that end was started meantime the mercur by consolidation with other properties had become the con consolidated soli dated mercur and the original mill at manning had been replaced by one in mercur which was for years the largest exclusive cyanide plant in the world and which still holds that position outside of south africa at the homestake Home stake in the black hills of south dakota is a tailings plant part of a combination combi process whose tonnage is greater than that of the mercur mill but the latter is a straight cyanide process and one who takes up the study of cyaniding cyan iding will find that an account of early progress at mercur will give a fairly accurate account of the development of cyaniding cyan iding in america and in almost every text book on the subject one finds a chapter headed mercur practice showing that even yet the metallurgist turns to this plant for an example of the best treatment of its particular class of ores the first sensation the visitor to this plant has is one of bewilderment there are so many different machines and process mine or more correctly speaking from the different mines is all dumped into pockets at the mill two of these compartments carry 24 ton skips working in balance one for each class of ore these when brought to the surface dump automatically into the two crude ore bins bans of steel well braced by columns from here on we shall trace the flow of each class of ore separately beginning with the base this passes a grizzly into a no 6 gates cates crusher dumping into a steel bin from which it is discharged through seven gates to a chute and into a hopper over an incline conveyor enve from here it passes successively ces three sets of gates high grade crushing rolls to an elevator which raises and dumps it into a the undersize from the goes goes to the pulp bin and the oversize to a fourth set of rolls 1 61 ram A all 2 k 0 N r iv A roasting furnace in the refinery of the mercur mill photo b lero A palmer as es that it is only after systematic study that one realizes that each one has its own work and contributes its particular part to a harmonious whole after twelve hours of close and hard study the mining review representative decided he had a general idea of the process which will be embodied in the following description and as he remarked to mr dern bern the manager he could pyo probably bably have gotten a pretty complete description by staying around a year or two character of ore the mine produces two classes of ore the oxidized and the base the latter containing arsenic and sulphur in quantities sufficient to seriously interfere with its treatment in a crude state the oxidized ore also possesses peculiarities of its own which necessitate an almost entirely aifer ent method of treatment theat ment for the two kinds the ore from the various parts of the which discharge to the no 2 elevator dumping into the bin in the chute to each set of rolls is a screen which takes out the fines and sends them to the no 2 elevator to be dumped with the product of the fourth set of rolls this makes a product no particle of which is over one fourth of an inch a desirable feature as all of this base ore must be roasted to expel the objectionable elements As this ore must all go through the furnaces it is crushed dry that the heat may wholly be utilized in driving off the arsenic and sulphur and none expended in drying the ore in cyaniding cyan iding the careful superintendent must watch closely two things his extraction of gold and his consumption of cyanide and he shows his skill in knowing when a further extraction of the precious metal will only be accomplished by such expenditure of cyanide and time as to make the operation unprofitable and in knowing when by spending additional money for this thing or that he can reduce his consumption or increase his extraction to the point that will turn the scale between profit and loss in that particular process roasting base ores in the case of the base ores of mercur it was found to be profitable to install large roasting furnaces to rid the ore of the interfering ter fering elements before subjecting it to the action of the cyanide solutions these furnaces are five in number and all embody the same principle but those giving the best satisfaction are the three designed by D C jackling now manager of the utah copper company who was at one time active in solving the metallurgical problems presented by mercur ores from the pulp bins the crushed ore discharges to a belt conveyor running in front of them which in turn dumps to others at right angles which feed the roasting furnaces A jackling furnace is feet long sixteen feet wide and three feet high with an arched roof of brick with plenty of cast iron doors in the side to allow of access to the interior on each side are two coal fed fire boxes in which the fire is maintained under the blast from a blower and a jet of steam is used to direct the flame downward onto the ore the ore dumps into a hopper at one end and is forced into the furnace by plunger feeders scrapers attached to an endless chain drag it slowly along the bottom of the furnace turning it over as it goes so as to subject every particle to the hot blast by the time the ore is dragged to 3 the other end of the furnace feet the arsenic and sulphur are expelled the roasted product is dumped to a chain elevator and raised to the cooling platform here sim r ilar scrapers drag it back to the end at T which it was fed turning it over and ex 5 posing it to the air and finally to finish the cooling process passing it under a spray of water before it is discharged by a screw to i the belt that conveys it to the bins above the leaching floor ll 11 the roasters asters ro take up the south end ov of 1 three floors the three Jac klings in one bierl A and in another tier two brown and one onela holthoff one of the brown furnaces howa how aa A 1 ever is out of commission and is being disi dis di s q 12 i mantled five being sufficient sum dent for the wor forkl kl the capacity pacify ca of each furnace is about seven p ty tons per day j t treatment of oxidized ores f ti from here we turn to the treatment 0 of ic the oxidized ore passing from the crude ore bins over a grizzly it is crushed in a I 1 duplicate of the crusher on the base sid 2 1 and dumped into bins from which it di d ai charges through gates to a horizontal caff conveyor 9 to a set of gates high grade rols which give it a preliminary crushing before it goes to a smaller set for finishing th the 0 product is then elevated and dumped into a th which discharges oversize and u uni Ider size into separate bins screens in the chutes to the rolls take out a portion of the fine ore which is raised in a second elevator and dumped into the bin that re 1 ceides 1 the undersize the oversize from the cont contains ains many pieces as large as an inch a feature which looks very peculiar to one acquainted with the usual cyanide practice but the porous nai ture of the ore allows the solution to per 1 beate these pieces as readily as the smaller I 1 ones indeed it was found that the first failure of the original plant was due to crushing too fine the friable slimy ore forming a thick mud when it received moist ure and thus preventing the solutions from acting properly the coarse oxidized ore is drawn off through the gates to a bin beside the one receiving the roasted base ore just above the leaching floor the latter is over feet long and contains 26 rectangular iron vats feet each having a ca of tons each vat has a cocoa matting and canvas bottom for flIt filtering ering and is provided with eight doors in the bottom for discharging the ore is crammed to the vats in cars the bottom of the vats being covered to a depth of two feet with the coarse oxidized ore and the vat then filled with roasted base ore this method of charging allows a free circulation of the solution and prevents packing of the ore the strong solution is then turned from athe the stock tank into the bottom of the leaching vat and allowed to run until the surface of the ore is covered after standing a short time the tank is tapped at the bottom and solution drawn off a sufficient amount being e run on at the top during 2 this operation to keep the ore constantly covered forty eight hours after first being turned on the strong solution is drawn off and replaced by a weak solution which is kept on seventy iwo two hours it is then replaced by wash water and after forty eight hours more or one week after treatment began the vat is ready for discharging the hanging doors covering the discharge holes are dropped down own and the leached beached out ore shoveled into pars ars placed underneath and hauled to the pump ump by horses f the strong solution as it runs from the apts ats is piped to a round steel tank in the precipitating 1 room and from there pumped lack ack to one of three tanks on a floor above here zinc fume is mixed with the solution to precipitate the gold after the zinc and nd the gold have combined to form a slime he e solution is drawn off to the filter presses he solution expelled under pressure and a cake ake of zinc gold slime remains this solution ion is pumped back and as weak alution ol ution the weak solution from the leach S vats is pumped back without precipitates 79 the gold to the strong solution tank and I 1 sufficient amount of cyanide added to lake ahe it a strong solution the company has been experimenting ith zinc shavings as a reagent for precipe tation and may make a change to that method the mercur slimes treatment this brings us to the slime system the latest installation and the one that seems to point to another era of profit making the nature of the ore is such that it slimes heavily and these slimes have not yielded to any method of treatment formerly in vogue and it was only after a year of experimenting that a successful slime process was evolved the ore from the fine oxidized bins is drawn off through gates and immediately mixed with strong solution which washes it to a set of two mixer separators in which it is successively treated these separators are a modified form of screw conveyor which conveys the coarse ore to the upper end while the solution washes the fines out of the lower end thus separating coarse and fine and mixing the fine with the solution this process is repeated in the second and the pulp goes to a cone settler which allows some of the lines fines to overflow the rim while the remainder goes to two dorr classi ayers here a series of blades scrape the ore toward the upper end of an inclined box while the solution tends to wash it toward the lower end the result is that the very fine washes out of the lower end of the box while the coarse particles offer sufficient resistance to the current to be carried to the upper end by the scrapers when this has been repeated in the second dorr classifier classi fyer the separation of sand and slime is almost perfect all of the sands run direct to a leaching vat and the slimes to one of three slime tanks here the excess of solution is decanted off and when the vat is full and the pulp thickened it is transferred to a vat from which it runs to the filter room here are four filter tanks with stationary filters through which the solution containing the dissolved gold is drawn off to the gold solution tank in the sump room and precipitating carried on in the manner just described the cakes of zinc gold slime are taken to the refinery nery where they are treated with sulphuric acid to dissolve the zinc the mass is then flIt filtered ered and dried and roasted in a large three muffle roasting furnace and run down into bullion with a flux of borax glass the refining furnace is fed with crude oil and has a capacity of pounds of the roasted product at a charge aside from the mill the property is equipped with machine shop and foundry at w which all ordinary repairs are made and all but the heaviest machine parts cast th the e water is pumped from ophir canyon seven miles distant by the gold belt water company in which the con mercur company is one half owner power is furnished by the telluride power company coming into camp under a tension of volts and being transformed to volts A few facts and figures figure s during the last fiscal year th the e con mercur showed a loss of seven cents per ton of ore treated while this balance is on the wrong side of the sheet it is really a remarkable showing when one considers that the year in question was one of the most trying through which the company has passed it has been conclusively proved that this company can make a profit only by continuously treating a large tonnage but during this time not only was the plant obliged to run for extended periods on low tonnage but was also totally shut down at one time and at no time was it run within ten per cent of its rated capacity of 1000 tons per day this was due chiefly to the alterations especially in the slime system that were continually going on added to this is the fact that an unusual amount of development work was undertaken much exploration was carried on and the old workings of two of the mines thoroughly opened up always an expensive proceeding this dead work was all charged to operating expenses and coming as it did all at once and during a period of limited production tended to throw the balance to the loss side plans are now under way for increasing the capacity of the slime system and with added by means of the work alluded to the con mercur should settle down to another era of comfortable prosperity but be as this accomplished and the large ore |