Black Oak Mine [1], Garden Valley, Kelsey Mining District, El Dorado County, California, USAi

Regional Level Types
Black Oak Mine [1]	Mine
Garden Valley	Unincorporated Community
Kelsey Mining District	Mining District
El Dorado County	County
California	State
USA	Country

A former lode Au mine located in sec. 27 & in the NE¼ sec. 34, T12N, R10E, MDM, 1.0 km (0.6 mile) ENE of Garden Valley (¾ mile NE of the GArden Valley School), on private land. The property was a small claim of 7 acres. Operated by R. J. Wilson. Operated prior to 1934 and during the period 1934 to 1942. MRDS database stated accuracy for this location is 100 meters.

This property was first worked as a pocket mine but had produced little. The activity in 1934 was proving successful with shipments of some ore rich enough to go direct to the smelter and some of milling grade was shipped to the Hart mill for crushing.

When visited (by California Regional Water Quality Control Board staff) the mine site was overgrown with crush. Waste rock was indistinguishable from the natural landscape. The surrounding soil did not appear reactive. One adit and one shaft were observed though neither showed evidence of discharge. No deleterious discharges were observed .

Mineralization is a vein deposit hosted in amphibolite, Late Jurassic Mariposa slate & schist. The ore body strikes NW and dips NE at a thickness of 3.66 meters. The plunge is 80 degrees. The depth-to-bottom is 115.82 meters and the length is 33.53 meters. The deposit is just N of where the Mother Lode splits into 2 branches, one to the N and the other to the NW. The vein is hosted in amphibolite schist that lies between 2 belts of Mariposa slate in the area. A strip of graphitic slate 50 feet wide forms the hanging wall. The main ore shoot of Au-bearing stringers and veins of calcite and quartz is wide in the N and pinches out to the S. The shoot follows, or is near the contact between graphitic slate and amphibolite. The Black Oak vein is 250 feet E of the Clark vein and 100 feet to the E is the Davenport vein zone. No ore was encountered below the 500 foot level. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).

Local geologic structures include tightly compressed, steeply-plunging folds with thrust faults dipping 20 to 35E that have disrupted contacts, and in some cases, localized Au mineralization. The main fault offset the vein and ore shoot 200 feet between the 400 and 500 foot levels. A small amount of Au was recovered below the fault.

Workings include underground openings. The mine is developed by extensive crosscutting from a 400 foot vertical shaft. Another shaft was sunk to the NW, with 6,000 feet of drifts and crosscuts. Both shafts are connected by crosscuts. In 1934, shallow workings were being worked at a depth of 55 feet with a small plant.

Production data are found in: Clark, Wm. B. & D.W. Carlson (1956).

Other Databases

Link to USGS MRDS:	10007027

Other Regions, Features and Areas containing this locality

References