Powellite from Marquette County, Michigan, USA
USA | |
| Morris Jr., T. (1983) Michigan Mineralogy: A Locality Index. Rocks & Minerals: 58(3): 111. & 61:328. |
| Heinrich, E. W., Robinson, George Willard (2004) Mineralogy of Michigan (2nd ed.) A.E. Seaman Mineral Museum and Michigan Technological University. 252pp. |
| Morris Jr., T. (1983) Michigan Mineralogy: A Locality Index. Rocks & Minerals: 58(3): 112. |
Travis Olds collection |
Superior gold & silver prospect, Ishpeming Greenstone belt, Marquette County, Michigan, USA