Opal from Riverside County, California, USA
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| Woodford, A.O., Crippen, R.A., and Garner, K.B. (1941) Section Across Commercial Quarry, Crestmore, California. American Mineralogist: 26: 351-381 (366). |
| DeVito, Fred, Ordway, Al (1984) The Jensen Quarry, Riverside County, California. The Mineralogical Record, 15 (5) 273-290 |
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Crestmore quarries, Crestmore, Jurupa Valley, Riverside County, California, USA