Moore Creek Mine (Moore Creek deposit; Bay Horse Mine; Whitehorse; White Horse Mine), Garnet Hill, Calaveras County, California, USAi

Regional Level Types
Moore Creek Mine (Moore Creek deposit; Bay Horse Mine; Whitehorse; White Horse Mine)	Mine
Garnet Hill	Hill
Calaveras County	County
California	State
USA	Country

A former Mo-Cu-W-Cu mine located in sec. 7, T7N, R16E, MDM, on the S side of Moore Creek, ½ mile SW of Garnet Hill, Moore Creek - Mokelumne River confluence area, on National Forest land. Operated during the period 1954 to 1957. MRDS database stated accuracy for this location is 1,000 meters.

Local rocks include Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges).

History
This property consists of a number of claims, the most important being the Moore Creek tungsten-molybdenum-copper mine. It is believed to have been prospected for copper during the 1860's, but nothing is known of these early operations. The property was prospected again during World War I, and a 40-foot adit was driven. In 1942, the property was prospected for tungsten by G.C. Bruce and C.R. Smith, but there was no reported production. In the fall of 1954, the newly organized Moore Creek Mining Company gained control of the property. This concern erected a mill and has operated the property since. In the fall of 1955 as much as 40 tons of ore per day was mined and milled, but since the price of tungsten and copper fell in 1957, only intermittent development work has been done.


Scheelite, molybdenite and chalcopyrite, with smaller amounts of pyrite and bornite are found in a series of discontinuous parallel lensoid tactite bodies. These bodies have a northeast strike, dip steeply to the southeast, and range from only a few feet to about 30 feet in thickness. So far, six such bodies have been exposed in the workings and by diamond drilling. Commonly, the tactite bodies are associated with several calcite-rich zones. Country rock in the general area is medium-grained diorite, granodiorite, gneiss, micaceous schist and massive granodiorite. The scheelite is moderately coarse-grained and is disseminated throughout much of the tactite. The copper sulfides, chiefly chalcopyrite, are erratically distributed in the tactite and are in irregular masses. Several masses more than a foot in diameter have been recovered. The molybdenite is in coarse flakes in much of the tactite and in fine flakes in disseminated form in some of the adjacent granodiorite. Ore mined in the fall of 1955 contained an average of one-half percent WO3.

Mine Development and Workings
Workings include surface and underground openings with a length of 97.54 meters, an overall depth of 4.57 meters, overall length of 12.19 meters and an overall width of 3.05 meters.

The mine is developed by a main 150-foot south cross-cut adit, several hundred feet up the steep slope south of Moore Creek, from which several short drifts and cross-cuts have been driven. Approximately 105 feet above the main adit is the old 40-foot adit and a quarry approximately 40 feet wide and 30 feet deep. At the mill, which is several hundred feet west of the main adit portal, the ore was sent through a jaw crusher, herman-type ball mill with a 16-mesh screen outside of the liners, and then to two rubber-deck Dunham tables where a tungsten concentrate was recovered. Table middlings, which contained the molybdenum and copper, were dewatered, sent to a conical ball mill, and then to a flotation unit. Flotation concentrates consisted of molybdenum, and the tailings contained copper, both of which were dried and stockpiled separately. Tungsten concentrates were cleaned by retabling and averaged 60 to 65 percent WO3. They were trucked to Fresno for magnetic separation and then sold in Bishop. Molybdenum concentrates were sold in San Francisco. The lessees built and operated a 50 ton per day gravity concentrator on the property.

Production data are found in: Stager (1965) and Clark, Lydon, Philip A. (1963).

Analytical data results: MoS2 = 0.08%; WO3 = 0.2% and Cu = 0.2%.

Other Databases

Link to USGS MRDS:	10008303

Other Regions, Features and Areas containing this locality

References