Clarkeite

Clarkeite is a uranium oxide mineral of with the chemical formula(Na,Ca,Pb)
2(UO
2)
2(O,OH)
3 or (Na,Ca,Pb)(UO
2)O(OH)•0-1H
2O.

Its color varies from dark brown to reddish orange. Clarkeite forms by oxidation and replacement of uraninite late during pegmatite crystallization. Although uraninite-bearing granite pegmatites are common, clarkeite is rare and occurs intimately intergrown with other uranium minerals.

It is known from only two localities; the Spruce Pine pegmatite district in western North Carolina, US, and Rajputana, in the Ajmer district, India. Clarkeite is the only known naturally occurring high-temperature uranate. The general formula for ideal clarkeite is Na[(UO
2)O(OH)](H
2O)
0–1.

It was named for Frank Wigglesworth Clarke (1847–1931), American mineral chemist, and former chief chemist of the United States Geological Survey.

See also

References
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