McCormick Mine (McCormick property; Terry and Sell lease [WWI]), Yosemite Junction, Tuolumne County, California, USAi

Regional Level Types
McCormick Mine (McCormick property; Terry and Sell lease [WWI])	Mine
Yosemite Junction	- not defined -
Tuolumne County	County
California	State
USA	Country

A former Cr mine located in sec. 2, T1S, R13E, MDM, 2.1 km (7,000 feet) SW of Yosemite Junction, along Mountain Pass Creek, on private land. Discovered in 1875. Operated from 1875 to 1957. Owned by Joseph W. Martin, Sonora, California 95370. Operated by A.E. and A.M. Hemming (North deposit); and by W.R. Williamson (South deposit) (1957-1976). MRDS database stated accuracy for this location is 10 to 100 meters (2 MRDS files).

Mineralization is hosted in the Josephine Ophiolite (dunite). The ore body is lenticular, disseminated & tabular, strikes N30-45W and dips NE (85E) at a thickness of 2.0 meters, a width of 61 meters and a length of 50 meters. The primary mode of origin was magmatic differentiation. Primary ore control was lithology and the secondary control was faulting. Wallrock alteration is intense (carbonitization & bleaching). The deposit consisted of 2 main ore bodies, North & South. Both had about the same strike and dip. The southern body was originally 165 feet long and had an average width of 4 feet and was highly faulted. The northern body was mined to a depth of 100 feet and had an average width of 3 to 6 feet. The deposit occurs in the northern part of the western part of 2 serpentine belts which trend NW-SE across the county. The belt is exposed over an area 30 km by 6 km. Associated rocks include diabase of the Logtown unit. Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).

Local structures include the NW-trending Bear Mountain Fault.

Workings include surface and underground openings. Workings of the southern deposit consisted of 3 shafts, 34 to 220 feet deep, and over 700 feet of drifts, crosscuts, raises and winzes. Workings of the northern deposit consisted of shafts and drifts, now caved (1944).

Production data are found in: Stinson (1975), CDMG Mineral Property Report, unpublished.

No more than 615 long tons of ore averaging 46.7% Cr2O3 remained unmined (cited from record 702). The mine was last worked in 1957. 144 long tons of milling grade ore was produced. 53 long tons were shipped. Analysis by the California DMG during 1976 are documented in MRDS file #10190541.

The 1950's production probably came from reworking of the mine dumps.

Analytical data results: Ore averaged 43-49% Cr2O3 and the Cr to Fe ratio was 2.8-3.5:1.

Other Databases

Link to USGS MRDS:	10190541

Other Regions, Features and Areas containing this locality

References