Carnotite
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.
| Carnotite | |
|---|---|
Carnotite in fossilized wood from St. George, Utah | |
| General | |
| Category | Vanadate mineral |
| Formula (repeating unit) | K2(UO2)2 (VO4)2·3H2O |
| IMA symbol | Cnt |
| Strunz classification | 4.HB.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | P21/a |
| 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 | |
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