Show TREATMENT OF MERCUR DUMPS by L 0 HOWARD M E H in the romance of a famous gold mine no mention was made of the treatment of tailings by the con mercur or constituent beyond the figures for tonnage included in the summary of results prior to the consolidation n the mercur gold mining and milling company treated a considerable tonnage of its old manning tailings the tailings were hoisted into the mill and without any additional crushing were charged into the leaching vats where they received identical treatment with the run of mine ore after the consolidation the company treated the tailings for a while in the manning mill they were scraped by horse scrapers into a trap from which a skip was loaded and the material hoisted to the mill bins from these bins it was d directly to the leaching vats without crushing the leaching was carried out in conformity i with the existing practice at the gold golden ra gate mill of the con mercur company following the line of flow used in the treat men of oxide ores there w were ere enuse in the neighbor neigh neighborhood bo lood of eighteen 30 foot by 5 toot foot leaching tanks zinc zin c dust was used as the precipitation agent generally the consumption of chemicals was as high as when leaching fresh ore before doin gany geany of this work some fifty tunnels had been driven into the dumps and assays essays indicated that the average value was about a ton there was estimated to be a tonnage of which could be treated at a profit of the first period of operation on company account extended from june 1901 to november 1902 with the exception of ther the month of march 1902 when no material was handled in this period the company treated tons of tailings the monthly tonnage ran from as low as up to in august 1901 the heads assayed from to the former figure applying toward the end of operations tails ran from to profits from 6 to 55 cents costs from 45 cents to details are shown in the accompanying table taking the results in this period from the records of the con mercur company as published in its annual reports we find that up to june 1902 not including june 1901 about aboul tons of tailings were retreated for a bullion recovery of at a cost of the extraction averaged cents at a cost of cents a ton leaving a net profit of cents a ton data are available in the table for figuring the head and tail assay and average extraction for this period for the following year the mill ing to the middle of november there was treated tons from which was obtained in bullion at a cost of extraction was 64 cents and cost 49 cents operations were stopped for the winter of 1902 1903 at this time plans were under way for the installation of the moore process at the golden gate mill and operations were not resumed at manning pending the success of that plant when it was intended to install it for treating the manning dumps the failure of the process at mercur meant that it would not be considered for the manning material inasmuch as the failure was due entirely to mechanical faults inherent in the apparatus used and had no connection with the character of material to be treated it was not until the middle of 1903 that anything further was done w when hen a lease on the mill and dumps was given but the lessees lessels were unable to gain any profit and 11 soon gave up they were responsible for one change however they precipitated with zinc shavings and all operation after that time involved involve d this method of precipitation the zinc dust equipment used by the company formerly having been moved to the golden gate mill after the failure of the lessees lessels les sees the company expended 1700 in repairing the mill and operations were resume resumed d on the of september and continued until december ath of the following year during this time with in intermittent operations the company treated tons of ore with a bullion production of and costs of 11 the per ton recovery was 64 cents and cost 54 cents the profit was therefore 10 cents a ton the mill was again leased and for the months of april may june and july lessees lessels paid in royalties at 30 cents a ton the costs to the company during this period are covered in the former figures for cost these lessees lessels finally gave tip ip the ghost the company made some more and improvements to the equipment and ran for 89 days from august 22 to november 21 1905 for this period tons were treated at a cost of cents a ton with a recovery of per cent 75 cents on heads running loss in tailings was the bullion recovered amounted to this marked the end of company opera eions on the manning dumps they had treated about tons for a production in bullion of about with a profit excluding royalties of over A good deal of base ore was mixed in the ore treated originally at manning and there being no ro asters used this fact ac counted counte d for the high tailings value before mentioned in pi previous evious art articles ioles and also was the undoubted reason that the retreated tailing jailing could not be treated with as little loss in the new tailings as was encountered in treating the mercur oxidized ores it would be expected that the treatment of tailings would result in a lower cyanide loss than in the treatment of fresh ores but the presence of some base in the original tails accounts for the high loss of cyanide in retreating tailings which was experienced in the companas comp anys operations the loss as before stated being about the same as in the treatment of the mercur ores at the golden gate mill as the manning leasing company in which the con mercur took a block of stock iu ili adjustment of its claims for unpaid royalty A portion of the above royalty was thus paid in stock in the new company the manning leasing company operated on the dumps from june 20 1908 to december 31 1911 with the exception of a six months period from january to june 1910 the manning leasing company treated tons of tailings on which it paid in royalty the expense to the con mercur for this period was the old manning mill having been dismantled in 1910 its parts being used up in connection with repairs at the golden gate frame alone was perforates the canvas was held out by strips placed at three inch intervals the frames themselves being spaced at six inch intervals in the tanks so that a three inch cake was built up of combined sand and slime the material went through a treatment usually arranged as follows the tailings were scraped by slip scrapers into chutes connecting with tunnels at the bottoms of the dumps and loaded into cars to be transported to the mill bins the cost of transportation por tation to mill was given as 1212 12 cents a ton fon the tails were ground in a one pound solution in two 6 foo foot t chili mills one M Y L 4 17 K Z V F mtv i ig 2 A VW MT V ka NN w v 7 1 cakl Ms F z ok the holderman holder man filter tank companas Comp anys plant the holderman filter tank company during the winter of 1905 the dumps were leased to the 1101 holderman derman filter tank company of salt lake which put in its own mill and process the plant was put in commission in july 1906 with a small capacity which was increased to a day from then until february 26 1906 this company treated tons on which it paid adal ties aggregating this was the profit to the con mercur company less 1 in general expense incurred on account of the manning property the company went into the hands of a receiver on the latter date and was later reorganized the holderman process the holderman process was peculiar in that it sought to treat a slime from which no attempt was made to separate the sand by a combination of leaching and leaf filter ing the company reported ported Te at one time an extraction of 70 per cent on heads running to 3 by grinding and simple leaching although although final estimates place the recovery at about on oil ore the essential apparatus of the holderman process consisted of a series of pulp tanks in ili which were suspended stationary filter leaves similar to the type universally used excy except pt that the bottom pipe of the akron and one using 35 and 40 horsepower respectively twenty mesh screens were used with the result that so 83 per cent of the pulp was minus 60 mesh and 40 to 50 per cent was minus the pulp containing 2 to 31 tons of solution to 10 one ne of ore and having an excess protective alkalinity of one pound of lime per ton flowed to one of eighteen 18 foot by 6 foot by 4 foot tanks set side by side and operated in units of three these tanks bad a bottom slope of two inches in one foot no agitation was used and the pressure due to the head in the tanks was sufficient to fro from draw the solution through the leaves a loosely compacted pulp and gradually dry it from eight to twelve hours was consumed in collecting and filtering after which a jet of clear water was used to stir up the cake and it and transport through three gates flush with the floor to launders leading to the lower tier of six tanks which were 18 feet by 6 feet by 7 feet in these tanks the leaves were submerged two feet and after filling with pulp to the top of the leaves clear water was added cautiously As the solution percolated the water took its place and gave a very good wash no further addition of cyanide was made in this series of vats the solution remaining from the first filtration being strong enough even when diluted with the clear water for the weak wash the pulp was finally s out with 40 per cent moisture by hose using water under 60 pounds pressure each tank had 33 leaves in the first series they were five feet long by three some details on of manning tailings by con mercur company month tons profit heads tails extraction cost per ton assay assay per cent per ton june 01 48 july 10 2683 august i 2955 september 2956 october november december january 02 51 february 47 march N 0 t 0 p e r a t e d april may 38 june 2796 july august september october november total and one half feet deep in the second series they were six feet long by four and one half feet deep under the low head used the leaves caked but little and needed cleaning but once a year handling solution the solutions both strong and weak were drawn off through cocks extending outside the tanks to a sump from which a centrifugal pump elevated them to a 16 foot diameter gold tank at the top of the mill in this tank were vere suspended seventeen leaves to act as clarifiers clari fiers and as a guard in case one of the slime filters broke after standardizing the solution was run to an 18 foot by 2 foot zinc box and re pumped to the stock tank the precipitates were shipped to smelters shelters sm elters without refining in 1909 the company claimed an extraction of 97 per cent of the soluble values a figure which I 1 hesitate to confirm the cyanide consumption was given as pounds and the zinc cost 1 cents per ton of ore treated costs on a ton basis were 70 cents per ton for treatment adding to this the cost of getting the fi fails ails to the mill and royalty would give a figure at any rate not under 1 per ton this should have left a handsome profit on 3 material and a not hot negligible one on material power power was brought from the mercur substation at volts and transformed to at the mill where it was used to drive the following motors 1 35 ir I r P driving akron chili mill 1 50 H P driving chili mill and pump for elevating solution from zinc box to stock tank 1 5 H P driving centrifugal pump lifting solution from sump to gold tank 1 5 H P driving rotary pump for sluicing twelve men operated the mill on three shifts ts summary considering the operations of the con mercur company the various lessees lessels and others close to tons of the considered available were treated with a probable recovery of some in bullion just what the profits were is difficult to say but it is probable that no one except the con mercur company made any profit out of these tailings and was able to hold on to it others sooner or later came to grief and after making profits for awhile had to suspend the con mercur made about profit on the dumps golden gate tailings of the tailings at the golden gate mill the con mercur company treated tons for the year ending june SO 0 1911 or about 12 per cent of its mill heads for the year many of the dumps were too low to pay and the profit from the others was small the dumps were tunneled the tailings hauled to a loading station on the and hoisted to the top of the mill where they joined the oxide ore and were treated with it the last four months of that year tailings made 24 per cent of the total material treated the cost of getting the tailings to the mill varied from cents to cents per ton during the next year tons were treated although not much was done with the tailings after august 1911 the cost for this period was 17 cents to get the tails to the mill this amount constituted seven per cent of the tonnage treated for the year the details are not at hand about the only effect was to lower the mill heads without reducing the loss in tailings or milling cost and some little profit resulted but not enough to make it an inducement to continue the treatment of tailings As matters now stand it is pretty evident that the tailings of both the manning and golden gate mills must await some new chemical process or some great development in existing processes either chemical or mechanical before the immense amount of gold tied up in them which a conservative estimate would place at between three and four million dollars shall circulate among men NOTE this is the fourth ofa of a series of articles on the mercur mining district the fifth artic article ile will appear in the next issue of the mining review editor |