Copper occurs in three minerals: chalcopyrite (CuFeS2), chalcosite (Cu2S), and malachite or verdigris (Cu(OH)2.2CuCO3). The latter is oxidized from the first two and is bluish-green. Brassy-gold colored chalcopyrite, which resembles fool's gold, is found in veins in Desmoinesian and older rocks in the Ozark, Ouachita, Arbuckle, and Wichita mountains. It has not been mined commercially. Chalcosite is dark brown and occurs in sheets and lenses in red beds of Pennsylvanian, Permian, and Triassic ages in western Oklahoma.
One chalcosite deposit, of Permian age, was mined near Creta, in southwestern Jackson County. From 1965 to 1976 Eagle-Picher Industries strip-mined a six- to twelve-inch-thick copper shale in the Flowerpot Formation. The bed averaged 1.8 to 2.2 percent copper, with some silver. About 1.5 million tons of ore was processed before the operation ceased due to copper's low price.
Another chalcosite deposit occurs in Triassic red beds of northwestern Cimarron County, near Black Mesa, and adjacent parts of Union County, New Mexico, and Baca County, Colorado. From 1884 to 1925 approximately two hundred mines were dug in this area, with about fourteen mines in Cimarron County. Chalcosite is disseminated in the Sheep Pen Sandstone along an unconformity at the top of the Triassic. The ore averaged less than 1 percent copper, with high-grade samples as high as 41 percent copper, with some silver and gold. The sandstone averaged about ten feet thick, with deep fillings in cracks two hundred feet deep. A mill was erected in Baca County, from which the ore was shipped to Pueblo, Colorado for smelting. About ten thousand tons of ore was mined in Oklahoma.
Robert O. Fay, Bibliography of Copper Occurrences in Pennsylvanian and Permian Red Beds and Associated Rocks in Oklahoma, Texas, and Kansas, 1805–1996 (Norman: Oklahoma Geological Survey, 2000).
Robert O. Fay, "Copper Deposits in Sheep Pen Sandstone (Triassic) in Cimarron County, Oklahoma, and Adjacent Parts of Colorado and New Mexico," Oklahoma Geological Survey Circular 86 (Norman: Oklahoma Geological Survey, 1983).
Robert O. Fay and Douglas C. Brockie, Metallic-mineral Resources of Oklahoma (Norman: Oklahoma Geological Survey, 2002).
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The following (as per The Chicago Manual of Style, 17th edition) is the preferred citation for articles:
Robert O. Fay, “Copper,” The Encyclopedia of Oklahoma History and Culture, https://www.okhistory.org/publications/enc/entry.php?entry=CO058.
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