This district is in south-central El Dorado County about 30 miles southeast of Placerville. It includes the Indian Diggings, Henry Diggings, Omo Ranch and Brownsville areas. Indian Diggings is best known as a placer-mining district, but there are a number of lode deposits. The Fairplay district lies to the west.
The district is underlain by quartz-mica schist, graphitic slate, green schist, quartzite, and limestone. The central part of the area has been intruded by a round quartz-diorite stock. Portions of the bedrock are overlain by patches of Terriary auriferous gravel and extensive andesite flows.
The channel gravels are part of the Terriary Mokelumne River, which extends south into this area from the Grizzly Flat district. The channel then extended west and southwest toward Fiddletown in Amador County. Indian Diggings was on a branch of this channel. Large amounts of gold came from these channel deposits, especially those at Indian Diggings, where the bedrock is limestone that contained numerous rich potholes. Mining was done by both hydraulicking and drifting. A number of narrow north-striking quartz veins in quartz diorite contain small but often rich ore shoots. The ore contains free gold and abundant pyrite, galena, and smaller amounts of other sulfides.
Placer: April Fool, Armstrong, Carrie Hale, Chic, Christion, Deep Channel, Dorsey, Drusy, Hayward, Hidden Treasure, Irish Slide, Last Chance, Little Bill, Lucky Jack, Old Chink, Omo, Patterson, Payne, Peacock, Richmond, Syracuse, Telegraph, Tomcat, Yellow Aster, Yellowjacket. Lode: Black Oak, Gold Note, Independence, Polar Bear, Potosi, Stillwagon.
Clark, W.B., and Carlson, D. W., 1956, El Dorado County, Placer deposits: California Jour. Mines and Geology, vol. 52, pp. 429-435.
Lindgren, Waldemar, 1911, Tertiary gravels of the Sierra Nevada: U.S. Geol. Survey Prof. Paper 73, pp. 180-181.
Lindgren, Waldemar, and Turner, H. W., 1894, Placerville folio, California: U. S. Geol. Survey Geol. Atlas of the U.S., folio 3, 3 pp.