Flintsteel Mine (Nassau Mine; Old Flintsteel Mine; Superior-Nassau Superior Mine), Mass City, Ontonagon Co., Michigan, USA
An underground copper mine consisting of one shaft (Nassau) and a series of pits (FlintSteel Pits). The company organized in 1853 as the Flint Steel River Mining Co. Work was suspended in 1858 and was dormant until 1863 when the company was reorganized as the Flintsteel Copper Co. The company merged with Caledonia in 1871. The Flintsteel produced approx. 870,000 lbs. of refined copper. The mine today is exceelent for copper, datolite, and good for silver.
Mineral List
9 entries listed. 6 valid minerals.
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References
Butler, B.S., and Burbank, W.S., 1929, The Copper Deposits of Michigan. U.S. Geological Survey. Professional Paper 144. 238 pp.
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