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Seneca #2 Mine (Gratiot Mine), Mohawk, Keweenaw Co., Michigan, USA
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Latitude: 47°18'54"N
Longitude: 88°20'44"W
The Gratiot Mine was opened by the Seneca Mining Company in 1910 to mine the highly profitable Kearsarge Lode. This mine is actually the Seneca No. 2 shaft but is referred to in most books as the Gratiot. In 1945, Calumet and Hecla Mining Company purchased the Gratiot Mine and operated it until 1966 when it ceased operation. Several minerals can be found at the rock piles that still exist, including copper, silver, epidote, prehnite, domeykite, and algodonite.

Mineral List


11 entries listed. 11 valid minerals.

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Kaminski-Hamka, T., 2011, The Copper Mines of Keweenaw County, Michigan. Copperlady Press, 150 pp.

The Copper Country Rock & Mineral Club, 2001, Red Gold and Tarnished Silver, 2nd Ed.

Clarke, D.H., 1976, Copper Mines of Keweenaw; Seneca Mining Co., no. 10, 24 pp.

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Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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