Opal from selected localities.
USA | |
| Reinhardt, E.V. (1951), Reconnaissance trip to Monument Valley, USAEL, RMO o. 624; Ridge, J.D. (1968), Ore deposits of the United States 1933-1967, Vol. 1: 799-803. |
Witkind, I.J. & R.E. Thaden (1963), Geology and uranium-vanadium deposits of the Monument Valley area, Apache and Navajo Cos., AZ: 95, 123. |