MOORE CREEK LEASING MILL. This mill built by Mr. Charles Moore at a cost of about $8,000 is a result of 14 years' experience at “creek leasings.” One special feature to be noticed in this mill is the manner of classification of the sands and the entire absence of crushing machinery. Total average heading to this mill is about 275 tons of solids per day, assaying 1 per cent Pb, 2 ounces Ag, and 2.5 to 3 per cent Zn. Fifty per cent of this amount is removed as oversize at the first trommel and first screen; 15 per cent of the total is slime overflow and is lost on the water wheel. Water in the creek averages about 1,500 gallons per minute for the year. During the early spring it is impossible to settle any slime on account of heavy flow of water from the melting snows. This lasts for four or five weeks. From the first of March until the first of August there is enough water in the creek to furnish power for running the mill. At other times it is necessary to run a 7-horsepower motor in addition to the water wheel, both of which are belted to a common line shaft, which drives all the machinery in the mill. A small dam, 2 feet high, catches the creek water and diverts it into a 12-inch by 13-inch launder. At the mill there is a one-half-inch screen set in the launder at about 45° to the direction of the flow, and this removes all one-half-inch oversize without allowing it to settle in the tanks. Large settling tanks check the velocity of the water and act as classifiers. The first settling tank is 19 feet by 19 feet by 7 feet high. Nearly all of the material which is coarser than one-half inch is caught in the first two compartments of this settling tank. The first two compartments discharge into the trommel screens, and the second two compartments discharge into a box with a one-half-inch screen to catch any oversize and wood chips that might be carried over. From the box the undersize goes into the second settling tank, 10 feet by 12 feet by 64 feet high, which has three compartments and discharges. Middlings from each table are shoveled into a hopper and are flushed back to the head of the table for re-treatment. Lead-iron concentrates and the zinc concentrates go into separate boxes at the end of the Wilfley tables, and from there they are shoveled into a wheelbarrow and then to their respective bins. When enough concentrate is stored up to make a shipment it is shoveled into a wagon and hauled to the railroad. The average output of this mill in 24 hours is 1 ton of zinc concentrates and about one-half ton of lead-iron concentrates. During the year 1914 this mill shipped 400 tons of zinc concentrates and 300 tons of lead-iron concentrates. Sulphur, 5 per cent allowed free, excess 25 cents per unit, $3 maximum. Speiss, 5 per cent allowed free, excess 25 cents per unit. Base treatment charge: $2 on a basis of 30 per cent Pb. Thus, for the lead-iron concentrate assaying 20 per cent Pb, 15 per cent Fe, 1.3 per cent Cu, 15 per cent Zn, 25 ounces Ag, 5 per cent SiO2, and 25 per cent S, the following would be the smelter returns (normal prices): Smelter contract with the Iola, Kans., zinc smelter up until the present year paid: Payment. Zinc, 80 per cent of zinc on a basis of 35 per cent Zn or better. Charges. Treatment charge, $15 per ton for 35 per cent Zn or better. Thus for the zinc concentrate assaying 2 to 3 per cent Pb, 8 per cent Fe, 39 per cent Zn, 0.5 per cent Cu, 13 ounces Ag, and 20-25 per cent S, the following would be the smelter returns, assuming normal prices: Average output of the mill is 1 ton of zinc concentrate and about one-half ton of lead-iron concentrate. From the sale of these concentrates- on an investment of $8,000. If the mill works 300 days a year this represents $4,536, or 56.6 per cent of the money invested. DALY WEST MILL. Ore from the mine is divided into two classes, milling and crude ore, according to the amount and character of the minerals contained. Zinc and silver are the determining factors. For instance, an ore containing over 15 per cent Pb and 20 ounces of Ag is usually shipped as a crude ore; however, if it contains a high percentage of zinc this ore may be sent to the mill in order to separate the zinc from the lead minerals. A smelter contract with the American Smelting & Refining Co. smelter at Murray calls for a very high base treatment charge and does not penalize for zinc. Therefore this mining company is not very careful to save the lead-zinc ores, especially if they contain high silver values. Both the crude shipping and the milling ores are complex ores of lead, iron, silver, zinc, and some copper in a gangue of quartz. As the oxidized zone does not extend below the 400-foot level, all of the ores now being shipped are sulphides. The lead occurs as coarse and granular galena; zinc occurs in various forms, the usual variety is the yellow resinous type of sphalerite; another type is the granular sphalerite (yellow), also resinous but very friable. Pyrite here found exists as small crystals in relatively small amounts. Copper is present only in very small amounts, but is found both as tetrahedrite and chalcopyrite. The silver is found existing in chemical and mechanical combinations with all of the above minerals. The ore is milled in a plant containing jigs, tables, and flotation machines, the latter being a more recent addition to the plant. Some data on this mill which is of interest is the following: For the month of May, 1915, the costs for the flotation plant: Pay roll, $150; power, $81.60; supplies, $15.98. This makes a total cost of $247.58. Assuming that the plant treated 25 tons per day of 31 days, the cost per ton of dry slime is $0.313. For the period of eight months ending November 1, 1915: Heading..... Concentrate. Tailing... Extraction. Test made on the Frantz jig efficiency by Stott, Nov. 3, 1916. Product to the mill is divided among the following ratios: There is not enough data at hand to calculate the losses after concentration, but from all appearances the results will be rather startling. For instance, an analysis of the concentrates shows: The loss of zinc in the lead concentrate and of lead in the zinc concentrate is a very common loss. DALY-JUDGE MILLING PRACTICE. Ore from the mine is divided into two classes, milling and crude ore, according to the amount and character of the minerals contained. Zinc and silver are the determining factors. For instance, an ore containing 12 to 15 per cent lead and less than 10 per cent zinc and 20 ounces of silver is shipped as crude lead ore. If it contains less lead or a higher percentage of zinc it is more profitable to treat in the mill and separate the lead and zinc minerals as far as possible. These Crude and milling ores are complex lead, zinc, iron, copper, and silver ores. sulphide ores are identical with those found in the Daly-West. Oxidation is limited to the 500-foot level except in fissure deposits where the copper sulphides especially have been altered to carbonate and oxides, yielding azurite, cuprite, and little chrysocolla. The depth of oxidation in the fissures is limited to the 1,200-foot level. Below this point oxidation is not important. The mill was designed to treat 150 tons of dry ore in eight hours. At the present time the mill is operating two shifts of eight hours each and is treating nearly 200 tons per day. SLIME TREATMENT AT THE DALY-JUDGE. Slime treatment in the past has been rather difficult owing to lack of suitable machinery. All the slime prior to November 1, 1915, was treated on Wilfley fine sand tables and Wilfley double deck "slimers." Average table concentration of slime feed for six months ending June 1, 1915: Owing to the complex nature of the minerals in the slime feed it has been found impossible to make a differential flotation, but it has been found necessary to float all the sulphides possible and then resort to separation on Wilfley tables. Thus we find a very complicated flow sheet, although flotation ordinarily tends to simplify operations. A 3-deck Dorr thickener, 30 feet in diameter, takes the slime overflow from the settling tank and three Richards-Janney classifiers. The thickened product contains approximately 15 per cent solids, of which 90 per cent will pass an 80-mesh screen. This seemingly thin pulp meets the flotation requirements to best advantage. A centrifugal pump elevates the pulp from the thickener to a mixing box, where the oil is added and a second centrifugal pump discharges the pulp into a 20-foot Pachuca tank, 4 feet in diameter, giving further mixing before going to the Callow flotation cells. 86198°-19-Bull. 168- 3 |