Page 110 - The Geology and Ore Deposits of Sierra County, New Mexico - Bulletin 10

MINING DISTRICTS 109
few instances have connected with raises driven on the same fracture from the tunnel level. Mr. Slease and the writer esti- mated that there are about 2,400 feet of workings in this mine, of which 1,000 feet consists of raises and winzes on pipes of ore, and from which, Mr. Slease believed, $100,000, or $100 per foot, had been recovered. The material shipped was broken by hand to pieces the size of a walnut and smaller, and only the pieces showing visible tellurides, together with the material too fine to inspect, were saved. Some of these shipments have assayed as
high as $85,000 per ton, while others, in which hessite (silver telluride) has greatly predominated, have assayed as low as $100 per ton. Mr. S. G. Lasky, assistant geologist on the staff of the United States Geological Survey, examined under the microscope polished sections of the rich ore from this mine with the writer, and it was found that the gold was in the free form and later than the silver telluride, and that it traversed the silver telluride in minute veinlets. No trace of gold was observed in any of the samples of the pure hessite examined chemically, but the ratio of the total gold and silver in many of the shipments was close to that of the mineral calaverite, and until quite recently this was considered to be the valuable mineral of the ore. The microchemical determination of hessite, however, with which free gold is associated in varying amounts, explains why