Refs.: Niemuth, N.J. (1987), Arizona Mineral Development 1984-1986, Arizona Department of Mines & Mineral Resources Directory 29, 46 pp.
Walenga, Karen (1987) New Operation to Double Arizona Gold Production: Southwestern Pay Dirt, No. 581: 4A-5A.
Spencer, J.E., Duncan, J.T., and Burton, W.D. (1988), The Copperstone Mine: Arizona’s New Gold Producer. Arizona Bureau of Geology and Mineral Technology Field Notes, vol. 18(2): 1-3.
Walenga, Karen (1988) Cyprus Starts Work on Underground Mine at Copperstone: Southwestern Pay Dirt, No. 592: 5A.
Minerals Today, US Bureau of Mines (Jan, 1990): 26.
Sawyer, M.B., Gurmendi, A.C., Daley, M.R., and Howell, S.B. (1992) Principal Deposits of Strategic and Critical Minerals in Arizona, U.S. Bureau of Mines Special Publication, 334 pp.
Peterson, E.K. and Dupree, J.A. (1993) Preliminary Investigation of Bulk Minable Gold Deposits, Colorado River Indian Reservation, Arizona and California, in: Manydeeds, S.A., and Smith, B.D., editors, Mineral Frontiers on Indian Lands: Bureau of Indian Affairs Division of Energy and Mineral Resources: 35-42.
MRDS database Dep. ID file #10056413, MRDS ID #TC00084; and, Dep. ID #10259110, MAS ID #0040120006.
A large former Au-Ag-Baryte (trace) property located in the NE¼ sec. 12, T6N, R20W, 18 miles S of Parker on the E side of the Colorado River, 12 miles N of Quartzsite, on BLM-administered land. The site consists of 290 unpatented mining claims leased by Cyprus, covering 5800 acres of federal land. Discovered 1979. First produced 1987. Owned by Cyprus Gold Co., a subsidiary of the Cypress Minerals Co. (Don Patch retains royalty rights)(1988). Operated by Morrison-Knudsen(1989).
Mineralization is a tabular deposit striking N30W and dipping 32NE with ore control by faults and brecciation and detachment faulting. Alteration is sericitization and some chloritization. Local structures include a probable fault separating Jurassic metamorphosed volcanic rocks and overlying sedimentary breccias derived from them. Moon Mountains Detachment Fault. The presence of quartz, hematite, and chrysocolla is a good indicator of gold mineralization.
The gold is in a breccia unit above a listric fault, in quartz latite below the listric fault, and in basalt plugs. The basalt plugs have the least mineralization. The listric fault is in the upper plate of a detachment fault. The mineralized contact zone extends horizontally for 3,000 feet (914.4 meters) and at least 1,000 feet down dip and is generally several tens of feet thick.
This mine will feature an open pit and development of an underground mine. The bench open pit will be 360 feet deep. Produced 1,953 kg Au (1988).
The life of this project is estimated at 7-9 years. No previous mining occurred at this site. Underground development was stopped by Cyprus in 1990 due to lower gold prices and because of caving ground conditions which required costly support methods. Cyprus may consider reaching the former underground mining targets from the surface. Copperstone was to have been the largest gold producer in Arizona and will more than double the state's 1986 gold output of 42,556 oz.
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Map Reference: 33°52'24"N , 114°17'23"W
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Mineral List:17 entries listed. 13 valid minerals.
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