Minesota Mine (Minnesota Mine), Rockland, Ontonagon Co., Michigan, USA
|Latitude & Longitude (WGS84):||46° 44' North , 89° 11' West|
|Latitude & Longitude (decimal):||46.73333,-89.18333|
|Köppen climate type:||Dfb : Warm-summer humid continental climate|
|Other regions containing this locality:||Keweenaw Peninsula, Michigan, USA|
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.
16 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
1000 - 1200 Ma
|Portage Lake Volcanics|
Age: Stenian (1000 - 1200 Ma)
Stratigraphic Name: Portage Lake Volcanics
Comments: This unit is the same as unit Yp on paper map of Sims (1992). Description is taken from that unit description.
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
Dana 6:22, 505 & 1086
Rocks & Minerals: 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.