Clear Creek County Colorado Gold Production
The Alice district is about 7 miles west-northwest of Central City in north-central Clear Creek County and extends into southwest Gilpin County. Most of the production of the district has come from the Alice mine, though little is known about its early history. The deposit probably was first mined in 1883. It was first worked as a placer by hydraulicking, and it yielded $60,000 in gold (2,903 ounces). Later the oxidized ore was treated in a stamp mill, and part of the free gold was recovered by amalgamation. The mill operated at a profit for 3 years until the oxidized ore was exhausted. Attempts to treat the unoxidized ore by concentration met with indifferent success; only about $10,000 (484 ounces) in gold concentrates was shipped (Bastin and Hill, 1917, p. 120, 325-326). The only other production recorded from the district is that of the North Star-Mann mine, which produced ore worth about $116,000 (about 5,610 ounces) through 1916 (Bastin and Hill, 1917, p. 329).
Apparently the district was abandoned for many years after the oxidized ore had been removed. The increased price of gold caused a brief revival from 1935 to 1941, during which time the upper enriched part of the sulfide zone was mined (Lovering and Goddard, 1950, p. 164). The district was largely idle from 1943 through 1959. Total gold production was at least 23,000 ounces through 1959.
The country rock of the Alice district consists mainly of schist of the Idaho Springs Formation which is interfingered with granite gneiss and Boulder Creek Granite, all of Precambrian age. A stock of quartz monzonite porphyry of Tertiary age intrudes the Precambrian rocks. The Alice mine ore body is a gold-bearing pyritic stockwork in the quartz monzonite porphyry; other mines in the district are in quartz-pyrite veins in the Precambrian rocks. The deposits were oxidized near the surface and contained 1 to 2% ounces of gold per-ton. A zone of supergene sulfide enrichment, containing 0.20 ounce of gold per ton, was found beneath the oxidized zone. The primary sulfide zone, beneath the supergene zone, contains only 0.03 ounce of gold per ton and is of too low grade to mine. Quartz and pyrite, some chalcopyrite, a little arsenopyrite, and local bismuth sulfide are the constituents of the primary ore. Sooty chalcocite and bornite are locally abundant in the supergene zone (Lovering and Goddard, 1950, p. 164-165; Bastin and Hill, 1917, p. 323-330).