Powellite from Okanogan County, Washington, USA
USA | |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Cannon, Bart (1975) Minerals of Washington. Cordilleran, Mercer Island, WA. |
| Cannon, Bart (1975) Minerals of Washington. Cordilleran, Mercer Island, WA. |