Clarkeite

Uranium oxide mineral
(repeating unit)(Na,Ca,Pb)
2(UO
2)
2(O,OH)
3 or (Na,Ca,Pb)(UO
2)O(OH)•0-1H
2OIMA symbolCke[1]Strunz classification4.GC.05Dana classification5.4.1.1Crystal systemTrigonalSpace groupR3m (No. 166)Unit cell239.11 Å3 (Calculated from unit cell)IdentificationColourDark red-brown, dark brownCleavageNone observedFractureConchoidal, sub-conchoidalMohs scale hardness4–4.5LusterResinous, waxy, greasyStreakYellow-brownDiaphaneityTranslucentSpecific gravity6.39Density6.39 g/cm3 (Measured)Birefringence0.111PleochroismWeak2V angleMeasured 30° to 50°, Calculated 32°DispersionRelatively weakOther characteristics Radioactive

Clarkeite is a uranium oxide mineral 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

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  • Clarkeite: New chemical and structural data
  • Clarkeite: Clarkeite mineral information and data
  • WebMineral


  • v
  • t
  • e