Chemistry:Clarkeite
| Clarkeite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | (Na,Ca,Pb)2(UO2)2(O,OH)3 or (Na,Ca,Pb)(UO2)O(OH)•0-1H2O |
| Strunz classification | 4.GC.05 |
| Dana classification | 5.4.1.1 |
| Crystal system | Trigonal |
| Space group | R3m (No. 166) |
| Unit cell | 239.11 Å3 (Calculated from unit cell) |
| Identification | |
| Colour | Dark red-brown, dark brown |
| Cleavage | None observed |
| Fracture | Conchoidal, sub-conchoidal |
| Mohs scale hardness | 4–4.5 |
| |re|er}} | Resinous, waxy, greasy |
| Streak | Yellow-brown |
| Diaphaneity | Translucent |
| Specific gravity | 6.39 |
| Density | 6.39 g/cm3 (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(UO2)2(O,OH)3 or (Na,Ca,Pb)(UO2)O(OH)·0-1H2O.
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[(UO2)O(OH)](H2O)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
- List of minerals
- List of minerals named after people
- Sodium uranate
References
- ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode: 2021MinM...85..291W.
- Clarkeite: New chemical and structural data
- Clarkeite: Clarkeite mineral information and data
- WebMineral
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