Bisbee daily review., 1916-08-06

COMMONWEALTH MINE PRODUCING GOLD AND
 SILVER CONSISTENTLY
Writer in Mining Magazine Tells of the improvements in Big Property at Pearce, Also Geological Formation.

Commonwealth property at Pearce, Arizona. is producing 9,0o0 ,o 10000 tons Of gold and silver ore per month. says ". A Scott in Mining ard Scien- tific Press, all of which is treated in the cyanide plant, which was built and equipped in 1913. The property is row under the management of A. H. Lawry. formerly of the Montana ronOpal:.
 The two veins or the property have almost an east-west striSa, ani dip about 60 degrees to tho scutn. or to- ward the body of the isolated hill. which rises from a level plain. The Main vein. which is the best producer, is on contact between rhyolite- brec- cia and andesite. although at the east end it is entirely within the andesite and sedimentary rock. Development and production are carried on through two incline shafts. reaching g depth of about 1 600 feet on the dip of the veins. The work done shows width of vein which varies considerably. It is 100 feet wide in sone parts Of the mine. The ore body. which occurs Tn shoots and channels. is found next to the footwall in some parts and on the hanging wall others; and. the foot wall itself is mineralized to a paying degree in some places. The gangue consists of quartz and calcite. carry ing silver and gold in the ratio or about l OF. gold to 100 Ozs. silver. It is said that manganese is associated with the gold and silver.
 The new incline serves as the main working shaft. the old incline being used for handling tools and supplies. The pump station, sn the Sth level, has triplex plunger pumps and one centrifugal, all electric riven, by which 1000. .OOO to l. .500,O0 gals. of water arc pumped to the surface daily. This supply of water is used for mill work and other purposes. The Sth level where the pump station is situated, IS 423 feet vertically from the surface. The 10th level is under water
 The source of power is steam plant. for which oil is used as /lel. The air compressor is steam driven. all other equipment about the min and mill being driven by electric mo tors. current for which is produced by generator, direct connected to a Corliss compound, condensing engine, developig $50 hp.
 The ore is dumped from mine skips into a receiving bin, chutes from which discharge the ore into saddle back. double discharge cars. These cars, operated by cable an dcounter balance, are hauled about 50 feet and the ore dumped into crusher bin or 65O tons capacity. This method or moving the ore from the shaft to the crusher bin is known as the C. w.. Hunt Co. automatic railway system, which is much used at coal mines. crusher bin, contains No. K. Gates gyratory crusher, operated by a lOo- hp. motor. by which the ore is crushed to Ain. size; it then passes through a revolving screen, 12 feet long. 4O-in. diameter. having IF in. holes, and running IS rpm. The oversize is re- crushed to 1la-mesh size by two No. K. gyratOry crushers. This l1a- mesh product is now delivered to a belt conveyor. 20 ins. wide, 27i feet long. running 250 feet per minute. on 20 degree incline. whereby it is conveyed up to the sampling plant, where the ore is sampled with stand ard equipment. The next step is to carry the ore by a 95-fOot belt con veyor to the battery bins. it being dis tributed to the several bins by self propelling reversing tripper These bins have a capacity of 500 tons, the ore discharging therefTom through six suspended Challenge feeders to the three 10-stamp battrs of 1850 lbs. each. The battery discharge is through and 4-mesh screens to three 5-toot Caldecott cones. The cone overflow passes to Dorr classifiers. the bot tom discharge is feed for three by 90 Hardinge mills The Hardinse product goes to Dorr classifiers. The Dorr and discharge passes to one i by 20foot and two } by 22fOot tube mills. which work in closed circuit; ' the Dorr overflow passing tO 3S by 12-foot Dorr thickener. Here the pulp is thickened to 1. and delivered to a 3S by 12-foot Dorr agitator. which works in continuous series with nine 3S by 12foot Pachuca tanks 1 The material is discharged from the Pachucas to four 42 by 12fOo; Dorr thickeners. in which the counter-cur-
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