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Minesota Mine (Minnesota Mine), Rockland, Ontonagon Co., Michigan, USA
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Latitude: 46°44'N
Longitude: 89°11'W
An underground copper mine consisting of eleven shafts and several adits located near Rockland, MI. The Minesota Mine was organized in 1848 and worked two fissure veins that were very rich in copper. The mine operated until 1885, when it was closed. The mine was consolidated into the Michigan Mining Co. holdings in 1899. The Minesota Mine produced approx. 34.7 million lbs. of refined copper.

The Minesota Mine got its name from an error in the recording of the original deed, when the second "n" was accidently left out. It was never changed, and the Minesota name hung around [the mine is nonetheless referred to as "Minnesota Mine" in numerous contemporanean reports; see e.g. Henwood (1871) and the references quoted therein]. The Minesota Mine was more famous for its exceptionally large masses of native copper discovered underground. It was not uncommon for masses up to 50 tons being discovered in the shafts and levels, but on March 7, 1857, a mass was discovered that would become the largest single mass of native copper ever found to this day. When processed, it was estimated to weigh around 527 tons (there were 27 tons of chisel chips produced from cutting up the mass!). Today, the collector can still find some of those chisel chips in the mine piles, as well as copper, silver, and micro minerals.

Mineral List

'Chlorite Group'
'K Feldspar'
'var: Adularia'

20 entries listed. 16 valid minerals.

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Henwood, W.J. (1871): Observations on Metalliferous Deposits: On the Native Copper of Lake Superior. Transactions of the Royal Geological Society of Cornwall 8(1), 385-489. [as Minnesota Mine]

Dana 6:22, 505 & 1086

Dana 7:I:101

Rocks & Min.: 58:112

Butler, B.S., and Burbank, W.S. (1929): The Copper Deposits of Michigan. USGS Prof. Paper 144, 238 pp.

Clarke, D.H. (1978): Copper Mines of Keweenaw: Minesota Mining Company, No. 11, 28 pp.

The Copper Country Rock & Mineral Club (2001): Red Gold and Tarnished Silver, 2nd Ed., 44 pp.

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