Powellite
| Colour | Yellow, Brown |
|---|---|
| Mohs hardness | 3.5-4 |
| Lustre | Adamantine |
| Streak | light yellow |
| Crystal system | Tetragonal |
| Transparency | Transparent |
| Cleavage | Indistinct on {011}, {112} and {001} |
| Fracture | Conchoidal |
| Chemical formula | CaMoO 4 |
| Specific gravity | 4.25 |
What is Powellite?
Powellite is a calcium molybdate mineral with formula CaMoO4. Powellite crystallizes with tetragonal – dipyramidal crystal structure as transparent adamantine blue, greenish-brown, yellow-to-grey typically anhedral forms. It exhibits distinct cleavage, and has a brittle-to-conchoidal fracture. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 4.25. It forms a solid solution series with scheelite (calcium tungstate, CaWO4). It has refractive index values of nω=1.974 and nε=1.984.
How to identify Powellite
- Lustre: Adamantine.
- Hardness: Mohs 3.5-4 — soft; a knife will scratch it.
- Streak: light yellow.
- Habit: Tetragonal crystal system.
Powellite in different forms
Stones often confused with Powellite
Frequently asked questions
How hard is Powellite?
Powellite is Mohs 3.5-4 on the hardness scale.
What colour is Powellite?
Powellite is typically yellow, brown (Straw-yellow, greenish yellow, yellow-brown, brown, colorless, may show blue to black zones).