Mokelumne Hill is in northwestern Calaveras County. It is both a placer- and lode-mining district and includes the Chili Gulch, Old Woman's Gulch, and Golden Gate Hill areas.
The streams in the area were placer-mined early in the gold rush. Mokelumne Hill, first known as Big Bar, developed as a mining camp in 1848. Chili Gulch was first known as Chilean Gulch, from the large number of Chilean miners who worked here. They were discriminated against and often were forced to leave the mining regions. There was also a number of French miners in the district who had disputes with the Americans. Later in the 1870s Chinese miners were active in this district in great numbers.
Large amounts of gold were recovered by hydraulicking and drifting, but ourput declined in the 1870s. The Quaker City, Boston, and other lode mines yielded substantial amounts of gold from the 1880s until about 1900. Mining was done in the district again in the 1930s, and there has been intermittent prospecting since. The gravels at Chili Gulch are now mined for aggregate. Many of the buildings in the old town of Mokelumne Hill are well preserved.
Geology and Ore Deposits
A complex system of Tertiary channels, extending south and southwest from Mokelumne Hill, included eight distinct channels and remnants of several others, which range from Eocene to Pliocene in age. The so-called Chili Gulch, Stockton Hill, and Deep Blue channels have been the most productive. These contain a high percentage of quartz pebbles and boulders. In places they also contain large clear quartz crystals, some of which are piezo-electric grade. Usually the channels are not more than a few hundred feet wide. Bedrock consists of slate, greenstone, and graphite schist.
The gold-quartz veins occur in the slate and greenÂ¬stone and are up to 50 feet thick. The gold occurs in the native state and is associated with small amounts of pyrite. Several dacite volcanic domes crop out in the district, and to the nonheast a granodiorite stock is exposed.
Placer: America, Chap pellet, Concentrator, Coffee Mill, Duryea, French Hill, Gopher, Green Mountain, Happy Valley, Hexter, Mosher, Neilsen, North Star, South Diamond, What Cheer, Werle. Lode: Boston $1 million, Easy Bird $300,000?, Hamby, Lamphear $122,000, Nuner, Quaker City $1 million+.
Clerk, W. B., and Lydon. P. A, 1962, Calaveras County, gold: California Division Mines and Geology County Rept. 2, pp. 32-93.
Holey, C.S., 1923, Gold placers of California: California Min. Bur. Bull. 92, pp. 147-148.
Knopf, A., 1929, The Mother lode system of California: U.S. Geol. Survey Prof. Paper 157, 88 pp.
Lindgren, Waldemar, 1911, Tertiary gravels of the Sierra Nevada: U.S. Geol. Survey Prof. Paper 73, pp. 205-209.
Logan, C. A., and Franke, H., 1936, Calaveras County, placer mines: California Div. Mines Rept. 32, pp. 324-355.
Ronsome, F. L, 1900, Mother lode district folio: U.S. Geol. Survey Geol. Atlas of the U.S., folio 63, 11 pp.
Storms, W.H., 1894, Ancient channel system of Calaveras County: California Min. Bur. Rept. 12. pp. 482-492.
Turner, H. W., 1894, Jackson folio; U.S. Geol. Survey Geol. Atlas of the U.S folio 11. 6 pp.