Location and History
This district is in east-central Nevada County about 30 miles east of Nevada City. It is also known as the Eureka district. An extensive belt of gold mineralization in this region extends from the vicinity of the town of Graniteville south-southeast to the Emigrant Gap district, a distance of about 10 miles. The district includes the Gaston mine area, which sometimes has been classified as a separate district. The Alleghany-Washington gold belt lies a few miles to the west, and the American Hill district is to the north. The Graniteville district was first placer-mined during the gold rush, and quartz mining began soon afterward. Considerable mining activity continued from the 1860's until about 1900, and there was much activity again during the 1930's. The Ancho-Erie and a few other mines were worked for a short time after World War II.
Geology
The district is underlain by slate, schist, and phyllite of the Blue Canyon Formation (Carboniferous) in the west and granodiorite in the east. In addition, there are several patches of Tertiary gravel and several glacial moraines.
Ore Deposits
Three main north-striking vein systems run through the district. One in the western portion of the district is in slate and schist and contains the Culbertson, National, and Ancho-Erie mines. One to the east is in granodiorite and contains the Wisconsin, Baltic, and Iowa mines. The veins in the central system are along the slate-granodiorite contact. Properties in the central system include the Rocky Glen and Gaston mines. The quartz veins are as mµch as 15 feet thick. The ore contains free gold and varying amounts of auriferous sulfides. The milling ore usually averages 1/2 ounce per ton or less with very little high grade. Some of the ore shoots had stoping lengths of several hundred feet. The veins were mined to depths of as much as 500 feet. The Tertiary gravels at Graniteville and at Shands two miles to the west have yielded some gold.
Mines
Alpha, Ancho-Erie $1 million+, Anderson, Artie, Azalie, Baltic, Barren, Birchville, Blue Bell, Celina Flat, Cooley, Culbertson, Eagle Bird, Gaston $2 million?, German, Gold Bug, Hotwater, Iowa, IXL, Jim, Keller, Last Chance, Lindsay, Mountain View, National, Rainbow, Rattlesnake, Republic, Rocky Glen $300,000+, Star, Washington, Wisconsin, Yellow Metal, Yuba $2 million+.
Bibliography
Hobson, J. B., and Wiltsee, E. A., 1893, Eureka mining district: California Min. Bur. Rept. 11, pp. 308-310.
Irelan, William, Jr., 1888, Eureka district: California Min. Bur. Rept. 8, pp. 448-451.
lindgren, Waldemar, 1900, Colfax folio, California: U. S. Geol. Survey Geol. Atlas of the U. S., folio 66, 10 pp.
Lindgren, Waldemar, 1911, Tertiary gravels of the Sierra Nevada: U.S. Geol. Survey Prof. Paper 73, p. 141.
Logan, C. A., 1930, Nevada County, Gaston mine: California Div. Mines Rept. 26, pp. 110 and 113.
Logan, C. A., 1941, Nevada County, Ancho and Erie group, Birch. ville mines: California Div. Mines Rept. 37, pp. 383 and 386.
MacBoyle, Errol, 1919, Nevada County, Graniteville mining district: California Min. Bur. Rept. 16, pp. 11-13.
