Precious Opal from
USA | |
| Anthony, J.W., et al (1995), Mineralogy of Arizona, 3rd.ed.: 193. |
| Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 282. Lewis, W. Scott (1942), Gem collecting in California: Hobbies: 47: 116-117 |