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| The mines are located along the contact zone between the Gold Hill monzonite porphyry stock and the surrounding Paleozoic limestone. The stock appears to be an intrusive and diatreme complex containing several breccia pipes. Numerous faults and fractures are present. Mineralization occurs in narrow zones along the contact breccias, in the limestone and along fractures in the porphyry. The mineralization widens in favorable ground associated with fracture systems, porous and permeable host rocks within the breccias and sedimentary rocks and in solution openings. The primary ore, gold and silver tellurides associated with fluorite and roscoelite, is oxidized in the upper levels of the mine. Some sulfides are present in the lower workings. The telluride ores of Gold Hill have been compared with those of the Cripple Creek District in Colorado , where mineralization extended to a depth of more than 3000 feet. |
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