Geologic description
This prospect contains a silver and gold-bearing carbonate-rich shear zone. The country rock is schist that strikes east-west and dips to the south at a shallow angle parallel to the schist (Brooks, 1913, p. 146). Prior to 1912, a 26-foot-deep shaft was sunk on the prospect and exposed the silver- and gold-bearing, carbonate-rich shear zone. In the summer of 1912, a 4- to 18-inch-wide cross-shear had been discovered on the prospect. A high grade sample from this cross-shear averaged over 820 ounces of gold per ton (Times Publishing Company, 1912). A 15-foot-deep test pit on this cross-shear exposed an east-west striking, steeply dipping quartz-bearing shear zone that varied from 3 inches to 2 feet wide (Smith, 1913, B 525; Brooks, 1913). The shear zone material was heavily stained by iron-oxides (Brooks, 1913, p. 146). Later phase, crystalline quartz vugs also contained iron-oxides after sulfides (Brooks, 1913, p. 146). By 1913, the shear zone had been traced for approximately 1,500 feet along strike and 1.5 tons of material had been stockpiled for later shipment to a nearby custom mill (Brooks, 1913, p. 146). Hill (1933) reported that exposures on the Plumbum prospect indicated the shear zone strikes N 70 W and dips 70 S. The prospect had not been worked for some time prior to 1931. |
