Obsidian from Colorado Plateau, USA
USA | |
| Robinson, Henry H. (1913), The San Franciscan volcanic field, AZ, USGS PP 76: 65. |
| Mitchell, 2001. Gem Trails of Arizona, p.56. |
| Robinson, Henry H. (1913), The San Franciscan volcanic field, AZ, USGS PP 76: 67. |
Robinson, Henry H. (1913), The San Franciscan volcanic field, AZ, USGS PP 76: 67. | |
Robinson, Henry H. (1913), The San Franciscan volcanic field, AZ, USGS PP 76: 67. | |
| Phillips, K.A. (1987), Arizona Industrial Minerals, AZ Dept. of Mines & Mineral Resources Rpt. 4. |
| www.swxrflab.net/mulecr.htm |
| Northrop, Stuart A., LaBruzza, F.A. (1996) Minerals of New Mexico (3rd ed.) University of New Mexico Press, Albuquerque, NM. |
Obsidian Tank, Parks, San Franciscan volcanic field, Coconino County, Arizona, USA