Location and History
This district is in west-central El Dorado County a few miles southwest of Placerville. It is in the Mother Lode gold belt and includes the Logtown area a few miles to the south of El Dorado. El Dorado, originally known as Mud Springs, was a camp on the Kit Carson emigrant trail before the beginning of the gold rush. There was much activity here during the gold rush and for some years afterward. The Church, Union and other mines were worked on a large scale during the 1890s and early 1900s. There was some work in the district again in the 1930s, but only minor prospecting since.
Geology
Slate of the Mariposa Formation (Upper Jurassic) occurs in the central portion of the district. Massive greenstone of the Logtown Ridge Formation (Upper Jurassic) is to the west, and granite rocks, schist and amphibolite lie to the east. The Mother Lode Belt here bends from the north to the northeast towards Placerville.
Ore Deposits
Most of the quartz veins in this district are confined to the slate, although a few are in greenstone and schist. They have north to northeast strikes and usually range from five to 10 feet in thickness. The ore contains free gold and pyrite and has an average content of about Yo ounce of gold per ton. Considerable high-grade ore was recovered from shallow workings. Much fault gouge is present. The greatest depth of development is about 2,000 feet.
Mines
Bidstrup, Buena Vista, Church $1 million, Crown Point, Crusader, German, Griffith, Larkin, Martinez, McNulty, Ophir, Pochahantas, Red Wing, Starlight, Tullis, Union $5 million?
Bibliography
Clark, W. B., and Carlson, D.W., 1956, EI Dorado County, lode gold mines: California Jour. Mines and Geology, vol. 52, pp. 401-429.
Lindgren, Waldemar, 1894, Placerville folio: U. S. Geol. Survey Geol. Atlas of the U.S., folio 3, .4 pp.
Logan, C. A., 1936, Mother Lode gold belt, Church and Martinez mines: California Div. Mines Bull. 108, pp. 21-22 and 30-31.
Storms, W. H., 1900, Church and Union mines: California Min. Bur. Bull. 18, pp. 91-92.
Tucker, W. B., 1919, El Dorado County, Church and Union mines: California Min. Bur. Rept. 15, pp. 283 and 299.
