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 late during pegmatite 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, in the Ajmer. 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.