Opal from San Franciscan volcanic field (San Francisco Peaks; San Francisco Mts), Coconino County, Arizona, USA
USA | |
| Hanson, S. L., A. U. Fastner, W. B. Simmons (2008) Mineralogy of the Fumerole deposits at Sunset Crater Volcano National Monument, Northern Arizona. Rocks & Mnerals 83:6 pp 534-544. |
| Tauber, Sebastian (2015) unpublished data on site visit. |