Powellite
Powellite is a rare member of the Scheelite group of minerals that also includes Scheelite, and Wulfenite. The chemical formula of Powellite is CaMoO4 and its molecular weight is 200.02 gm. Powellite is an extremely rare gem, among the rarest of collector’s gems. Powellite has a specific gravity of 4.26 (g/cm3) and the refractive index of 1.974 – 1.984 Uniaxial ( + ). Moh’s Hardness is 3.5-4.0. Prior to a discovery of Powellite crystals at Pandulena Hill, Nasik District, Maharashtra, India it was unknown as a gem. Gem quality crystals have since been found in the Jalgoan District of India as well. The transparent crystals from these locations are very small so gems are also small. There are several other locations worldwide where Powellite is found but none produce gem quality crystals.
| Category: | Molybdate minerals |
| Chemical Formula: |
CaMoO4 |
| Crystallography: | Tetragonal – Dipyramidal |
| Crystal Habit: | Crystals are usually dipyramidal, less commonly flat tabular to paper-thin, with many minor forms, to 8 cm; may be aggregated into crusts, pulverulent, ocherous, massive. |
| Twinning: | None |
| Composition: | Calcium | 20.04 % | Ca | 28.04 % | CaO |
| Molybdenum | 47.97 % | Mo | 71.96 % | MoO3 | |
| Oxygen | 32.00 % | O | |||
| 100.00% | 100.00% | =TOTAL OXIDE |
| Cleavage: | [112] Indistinct, [011] Indistinct, [001] Indistinct |
| Fracture: | Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 3.5 – 4.0 |
| Density: | 4.26 (g/cm3) |
| Luminescence: | Fluoresces creamy white or yellow to golden yellow under SW UV. |
| Radioactivity: | Not Radioactive |
| Color: | Colorless, Straw Yellow, Greenish Yellow, Yellowish Brown, Brown; may be zoned, Blue to nearly Black |
| Transparency: | Transparent, Translucent |
| Luster: | Sub-Adamantine, Resinous, Pearly |
| Refractive Index: | 1.974 – 1.984 Uniaxial ( + ) |
| Birefringence: | 0.011 |
| Dispersion: | 0.058 (higher than Diamond) |
| Pleochroism: | In deeply colored specimens; O = blue; E = green |
