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USA | |
| Bernstein, Lawrence (1980) Minerals of the Washington D. C. area: Maryland Geological Survey Educational Series 5, 148 pp. Rocks & Minerals 12, 247 |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Beard, R. (2015) Rockhounding Delaware, Maryland, and the Washington, DC Metro Area. Chapter 32: 122-123. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Ref: Minerals of the Washington, D.C. Area |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Ref: Minerals of the Washington, D.C. Area |
| Personally Collected by Stuart Herring |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Minerals of the Washington, D.C. Area |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| (2005) Mineral Resources Data System (MRDS), US Geological Survey. |
| Jat Thompson |