The Big Oak Flat district is in the East Gold Belt of the Sierra Nevada in southwestern Tuolumne County. It includes the Groveland, Deer Flat, and Second Garrotte areas to the east.
This district was first mined shortly after the beginning of the gold rush by James D. Savage. It was named for an oak tree that had a trunk with a diameter of 11 feet. The placer deposits here were highly productive, those at Big Oak and Deer Flat having been credited with a production of $25 million. Lode mining began soon afterward, and continued steadily until World War 1. The town of Garrotte was renamed Groveland by later residents who replaced the name given in 1850, when a thief was hanged there. But a place to the east, named Second Garrotte (after 1850) for a similar reason, has kept its 19th Century name. This area has prospered from tourist trade that originates along the Big Oak Flat road, which serves Yosemite National Park. The Hetch Hetchy Railroad, which was used in the construction of the San Francisco Water Department's Hetch Hetchy Reservoir to the east, served the area for some years. Some lode mining was done in the district again in the 1930s, and there has been intermittent. prospecting and development work at several mines since.
The area is underlain by a northwest-trending belt of schist, argillite, and quartzite of the Calaveras Formation (Carboniferous to Permian), intruded by several small granodiorite stocks and flanked on the west by amphibolite, slate, and serpentine of the Mother Lode belt.
A considerable number of north, northwest and west-trending quartz veins are found in both the metamorphic rocks and the granodiorite. The are shoots usually are limited in extent, but often are rich. The ore contains free gold and often abundant sulfides, especially galena. Most of the veins are only a few feet thick. The surface placers mined during the gold rush were extremely rich.
Bicknell, Champion, Contact, Criss Cross, Del Monte, Goodnow, Kanaka, Long Fellow $100,000+, Mack, Mississippi, Mohrman $40,000, Mt. Jefferson, National, Nonome, Red Jacket, Rhode Island, Venus, Wide West.
Logan, C. A., 1949, Tuolumne County, lode gold: California Journal of Mines and Geology, vol. 45, pp. 54-73.
Ransome, F. L, 1900, Mother Lode district folio: U. S. Geol. Survey Geol. Atlas of the U. S., folio 63, 11 pp.
Tucker, W. B., 1916, Tuolumne County, Big Oak Flat and Grovelond district; California Min. Bur. Rept. 14, p. 136.
Turner, H. W., and Ransome, F. L., 1897, Sonora folio: U. S. Geol. Survey Geol. Atlas of the U.S., folio 41, 7 pp.