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Columbia Mine | |
Alternate NamesSilent Friend, Tumacacori, Wolfe & Farmer, Rawson CompanyNone known Mining District and MinesNogales District
LocationOn Mount Benedict, north of Nogales 23S 14E NW¼ 285 31.4032N, 110.92596W4 Mineral ProductsAu, Pb, Ag, Cu-.5 Shaft, tunnel, adit, pit and open cut operations. Worked sporadically from prior to 1900 to 1941 producing some 100 tons of ore averaging about 5% Pb, 5 oz. Ag/T, 0.5 oz. Au/T, and up to 0.55 Cu.5 GeologyThe Columbia mine is on the northwest slope of Mount Benedict, at an elevation of about 4,040 feet. It is developed by about 500 feet of work, which includes an 80-foot shaft, a 300 foot tunnel, and a winze. It has produced some fair grade ore, mostly from the winze. The country rock is quartz monzonite. In one part of the workings it contains a large body of massive quartz which, together with quartz monzonite, is cut by dark-greenish diorite that is transversed by calcite veinlets The deposits occur in two east-west veins about 250 feet apart, of which the north or principal vein strikes N. 80° E. and dips 50° S. in the quartz monzonite and quartz. It consists in part of massive quartz, crushed, sheared, altered quartz monzonite, and dark intrusive diorite. It is 4 feet in maximum width, but the portion worked is only about 1¾ feet wide and consists of principally of banded quartz and mineralized rock. The vein is opened by a 40 foot open cut and the 80 foot shaft. The south vein strikes N. 80° W. and dips 60° S. in hard quartz monzonite. It is about 1½ feet in maximum width and consists principally of banded quartz contain galena, pyrite, chalcopyrite, and some malachite stain.2 Irregular shear zones containing banded lenses of quartz, and crushed, sheared, and altered Jurassic quartz monzonite showing partially oxidized and spotty gelena, pyrite and chalcopyrite. Associated dark lamporphyritic dikes.5 References
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