| Clarkeite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | (Na,Ca,Pb) 2(UO 2) 2(O,OH) 3 or (Na,Ca,Pb)(UO 2)O(OH)•0-1H 2O |
| IMA symbol | Cke |
| Strunz classification | 4.GC.05 |
| Dana classification | 5.4.1.1 |
| Crystal system | Trigonal |
| Space group | R3m (No. 166) |
| Unit cell | 239.11 Å (Calculated from unit cell) |
| Identification | |
| Colour | Dark red-brown, dark brown |
| Cleavage | None observed |
| Fracture | Conchoidal, sub-conchoidal |
| Mohs scale hardness | 4–4.5 |
| Luster | Resinous, waxy, greasy |
| Streak | Yellow-brown |
| Diaphaneity | Translucent |
| Specific gravity | 6.39 |
| Density | 6.39 g/cm (Measured) |
| Birefringence | 0.111 |
| Pleochroism | Weak |
| 2V angle | Measured 30° to 50°, Calculated 32° |
| Dispersion | Relatively weak |
| Other 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(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
- 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
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