Carnotite
| Carnotite | |
|---|---|
|
Carnotite in fossilized wood from St. George, Utah | |
| General | |
| Category | Vanadate mineral |
| Formula (repeating unit) | K2(UO2)2(VO4)2·3H2O |
| Strunz classification | 04.HB.05 |
| Crystal system | Monoclinic; 2/m |
| Space group | Monoclinic 2/m |
| Unit cell | a = 10.47 Å, b = 8.41 Å, c = 6.91 Å; β = 103.83°; Z = 2 |
| Identification | |
| Color | Bright yellow to lemon-yellow, may be greenish yellow. |
| Crystal habit | Crusts, earthy masses, foliated and granular aggregates. |
| Twinning | On {001} as both twin and composition plane |
| Cleavage | Perfect on {001}, micaceous |
| Fracture | uneven |
| Mohs scale hardness | 2 |
| Luster | Dull, earthy; silky when crystalline |
| Streak | yellow |
| Diaphaneity | Semitransparent |
| Specific gravity | 4.70 |
| Optical properties | Biaxial (-) |
| Refractive index | nα=1.750 - 1.780, nβ=1.901 - 2.060, nγ=1.920 - 2.080 |
| Birefringence | δ = 0.200 |
| 2V angle | Measured: 43° to 60°, Calculated: 26° to 36° |
| Other characteristics | Radioactive, not fluorescent |
| References | [1][2][3][4] |
Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K2(UO2)2(VO4)2·3H2O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present.
Occurrence
Carnotite is a bright to greenish yellow mineral that occurs typically as crusts and flakes in sandstones. Amounts as low as one percent will color the sandstone a bright yellow. The high uranium content makes carnotite an important uranium ore and also radioactive. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates.
In the United States it is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone[1] and concentrations around petrified logs. It also occurs in the U.S. states of Wyoming, Colorado, Arizona and Utah. It also occurs incidentally in Grants, New Mexico and Carbon County, Pennsylvania.[5]
Carnotite is reported in Congo (Kinshasa), Morocco, Australia (Radium Hill) and Kazakhstan.[5] In Pakistan carnotite occurs in the Upper Miocene middle Siwaliks sandstone (Dhokpathan Formation), in the vicinity of Takhat Nasrati, Karak District.
Name and discovery
The mineral was first described in 1899 by French scientists M. M. C. Freidel and E. Cumenge, who identified it in specimens from Roc Creek in Montrose County, Colorado, United States.[6] It is named for Marie Adolphe Carnot (1839 - 1920), French mining engineer and chemist.[3]
Related mineral species
Several related mineral species exist, including: margaritasite ((Cs,K,H3O)2(UO2)(VO4)2·H2O) and tyuyamunite, (Ca(UO2)2(VO4)2·5-8H2O).
See also
References
- 1 2 Handbook of Mineralogy
- ↑ Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York ISBN 0-471-80580-7
- 1 2 Mindat.org
- ↑ Webmineral
- 1 2 Mindat with locations
- ↑ Robert J. Wright and Donald L. Everhart (1960) Uranium, in Mineral Resources of Colorado First Sequel, State of Colorado Mineral Resources Board, p.330-331.
External links
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