This district is in northwestern Tuolumne County in the general vicinity of American Camp Station, which is about eight miles northeast of Columbia. It includes the Italian Bar, French Camp, Star Ridge, Grant Ridge, and Cedar Ridge areas. The famous Columbia placer-mining district adjoins it on the southwest.
The streams in the district were first mined during the gold rush. The town of Italian Bar was the principal settlement at that time. It later was destroyed by fire. Lode mining began about 1860, and continued almost steadily until around 1900. There was some mining in the district again in the 1920s and 1930s, and there has been minor prospecting since. The Grant mine was prospected for uranium in 1953-54.
The district is underlain predominantly by argillite, quartzite, siliceous schist, and limestone of the Calaveras Formation (Carboniferous to Permian). There are also a few small granodiorite stocks. Finegrained diorite and aplite dikes are common and are often associated with the gold-quartz veins. Ore deposits. Numerous gold-quartz veins and stringers contain small to medium-sized ore shoots. The veins strike either west or north-north-east. In places the ore is rich. The ore contains free gold associated with varying amounts of sulfides, especially galena and chalcopyrite. There are several patches of Eocene channel gravels that have been mined by hydraulicking. At the Grant mine black uraninite associated with gold occurs in quartz.
Argentum Consolidated, Black Bear, Contention, Gold Ridge, Grant, Gray Eagle, Ham and Birney $100,000, Hazel Bell, Indian Girl, Keltz $300,000, Lucky Strike, Mountain Lily, Noonday, Rifle, Sonnet, Star, Tiffany, Volunteer.
Goldstone, L. P., 1890, Tuolumne County, Keltz mine: California Min. Bur. Rept. 10, pp. 755-757.
logan, C. A., 1928, Tuolumne County, gold quartz mines: California Oiv. Mines, Rept. 24, pp. 8-21.
Turner, H. W., and RoÂ·nsome, F. L., 1898, Big Trees folio: U. S. Geol. Survey Geol. Atlas of the U. S., folio 51, 8 pp.