The Grizzly Flat district is in south-central El Dorado County about 25 miles east of Placerville. It is in the Sierra Nevada east gold belt and includes the Hazel Valley and Baltic Peak areas. It is both a lode and placer gold-mining district.
The streams were originally mined during the gold rush. The camp was established in 1850 and named for a grizzly bear that surprised a group of miners during an evening meal. The Mt. Pleasant mine was discovered in 1851. There was much activity in both the lode and placer mines from the 1870s through the early 1900's. There was some mining activity again during the 1930s. The Hazel Creek mine was discovered in 1948 and was worked on a fair-sized scale until 1958.
The southern part of the district is underlain by granodiorite, which extends west from the mass of the Sierra Nevada batholith. To the north is slate, phyllite, and graphitic and mica schist of the Calaveras Formation (Carboniferous to Permian), which in places contains small tactite bodies. There are several patches of Tertiary gravels overlain by andesite that are part of the south-extending Tertiary channel of the Mokelumne River.
A number of north-trending quartz veins and stringers are found in both the granodiorite and metamorphic rocks. The ore contains free gold and abundant sulfides, especially galena. The ore averages 1/2, to more than one ounce of gold per ton, but few ore shoots were more than 100 feet long or attained much depth. The Tertiary channel gravels are thin and the channels narrow, but in some places they were extremely rich.
Lode: Blue Gouge, Cosumnes (Melton) $100,000+, Daily and Bishop, Eagle, Eagle King, Hazel Creek $1 million+, Morey, Mt. Hope, Mt. Pleasant $1 million+, Sunday. Placer: Grizzly Flat drift, Payne drift.
Clark, W.B., and Carlson, D. W., 1956, El Dorado County, Blue Gouge, Cosumnes, and Hazel Creek mines: California Jour. Mines, vol. 52, pp. 411, 413, and 416-418.
Irelan, William, Jr., 1888, Grizzly Flat district: California Min. Bur. Rept. 8, pp. 177-180.
lindgren, Waldemar, and Turner, H. W., 1894, Placerville folio: U.S. Geol. Survey Geol. Atlss of the U.S., folio 3, 3 pp.
Lindgren, Waldemar, 1911, Tertiary gravels of the Sierra Nevada: U.S. Geol. Survey Prof. Poper 73, pp. 180-181.
Logan, C.A., 1938, El Dorodo County, Blue Gouge, Melton, and Mt. Pleasant mines: California Div. Mines Rept. 34, pp. 224-225, 238, and 241-242.
Tucker, W.B., 1919, El Dorado County, Eagle King and Mt. Pleasant mines: California Min. Bur. Rept. 15, pp. 285 and 292.