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USA | |
| Rosemeyer, T. (1996) The Cliff: America's First Native Copper Mine. Rocks & Minerals: 71(6): 381-390. |
| Larry Maltby, verified by Dr. Robinson and Dr. Jaszczak, Raman Spectroscopy |
| Heinrich, E. W., Robinson, George Willard (2004) Mineralogy of Michigan (2nd ed.) A.E. Seaman Mineral Museum and Michigan Technological University. 252pp. |
| Rosemeyer, T. (2009) Copper-bearing Fissure Veins, Keweenaw County, Michigan, Lake Superior Native Copper District. Rocks & Minerals: 84(4): 298-323. |
| Heinrich, E. W., Robinson, George Willard (2004) Mineralogy of Michigan (2nd ed.) A.E. Seaman Mineral Museum and Michigan Technological University. 252pp. |
Clark Mine, Copper Harbor, Grant Township, Keweenaw County, Michigan, USA