Multiple Oxides

Multiple oxides are compounds of two metallic elements with oxygen, as in chromite, FeCr2O4. Some of the multiple oxides are soft, but many are hard and can be used as gemstones when transparent and flawless. Chesterman, p. 415

# Sources[edit]

* Chesterman, Charles W. The Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf: New York (1987)