Alta Hill Mine (Alta Hill; Alta Hill Chrome Mine), Grass Valley, Grass Valley Mining District, Nevada County, California, USAi

Regional Level Types
Alta Hill Mine (Alta Hill; Alta Hill Chrome Mine)	Mine
Grass Valley	Valley
Grass Valley Mining District	Mining District
Nevada County	County
California	State
USA	Country

A Cr-Fe occurrence located in sec. 22, T16N, R8E, MDM, about 2.2 km just W of N of Grass Valley proper, SW of the Nevada Union High School and N of the Alta Hill Reservoir (on the N side of the road between Grass Valley and Nevada City), on private land. Discovered and first produced in 1918. Owned & operated by W. F. Mau, O. R. Heidrick, and L. W. Williams, California (1976). Operated by A.A. Codd who leased the mine during the latter part of 1918. MRDS database stated accuracy for this location is 500 meters.

The ore body strikes N00W and dips 85N at a width of 15 meters. It is a lenticular body. The primary mode of origin was magmatic differentiation. Primary ore control was lithology. Wallrock alteration is moderate (carbonitization). Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).

Workings include surface and underground openings. There are 2 groups of workings about 100 feet apart, comprised of some open cuts and 2 shafts at 20 feet and 30 feet deep, respectively, with a drift of about 50 feet.

Cameron visited the property and found the ore in the lenses was low-grade material. The ore contained 31 to 36% Cr2O3.

A state report indicated about 250 tons of milling-grade ore containing 15 to 18% Cr2O3 was produced with about another 150 tons shipped in 1918. Williams reported shipments of only 117 long tons and stocks of 61 tons in 1918. In 1937 Williams sold about 60 long tons. Some of the ore shipped contained 31 to 36% Cr2O3.

Other Databases

Link to USGS MRDS:	10031754

Other Regions, Features and Areas containing this locality

References