Boise County Idaho Gold Production
The Quartzburg (Gold Hill, Granite, and Placer-ville) district is in T. 7 N., R. 4 E., near the town of Quartzburg.
Soon after the initial placer mining rush to the Boise Basin, lode mining began in the Quartzburg district. The Gold Hill mine, discovered in 1863, was worked almost continuously until 1938 (Anderson, 1947, p. 176). Other important producers were the Mountain Chief and Belshazzar mines.
Ross (1941, p. 20) mentioned a total of $8 million (about 400,000 ounces) in gold from this district; however, the district was virtually idle from 1940 through 1959. Production since 1932 must have been combined with production reported from other districts because this district does not appear in the annual volumes of "Minerals Yearbook."
The Quartzburg district is at the southwest end of the "porphyry belt" that crosses the northern part of Boise Basin. The country rock is quartz monzonite of the Idaho batholith which was cut by northeast-trending shear zones, which in turn were intruded by porphyry dikes during Miocene time (Anderson, 1947, p. 129-150; Jones, 1917, p. 89-97; Ross, 1933a, p. 330-331). The gold lodes are fissure veins and small stockworks in or along the dikes and in adjacent quartz monzonite. The deposits are extensively oxidized, and most of the early production came from this easily treated ore which had high gold content. The hypogene minerals are py rite, galenobismutite, arsenopyrite, native gold, sphalerite, tetradymite, pyrrhotite, stibnite, chalcopyrite, and either tetrahedrite or tennantite. Gangue consists primarily of altered host rock and quartz (Ross, 1933a, p. 339-341).