Prehnite
| Colour | Green, Yellow, Clear, Gray |
|---|---|
| Mohs hardness | 6–6.5 |
| Lustre | Vitreous to pearly |
| Streak | White |
| Crystal system | Orthorhombic |
| Transparency | Semi-transparent to translucent |
| Cleavage | Distinct on [001] |
| Chemical formula | Ca 2 Al(AlSi 3 O 10 )(OH) 2 |
| Specific gravity | 2.8–2.95 |
What is Prehnite?
Prehnite is an inosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2 with limited Fe3+ substitutes for aluminium in the structure. Prehnite crystallizes in the orthorhombic crystal system, and most often forms as stalactitic, botryoidal, reniform or globular aggregates, with only just the crests of small crystals showing any faces, which are almost always curved or composite. Very rarely will it form distinct, well-individualized crystals showing a square-like cross-section, including those found at the Jeffrey Mine in Asbestos, Quebec, Canada. Prehnite is brittle with an
How to identify Prehnite
- Lustre: Vitreous to pearly.
- Hardness: Mohs 6–6.5 — about as hard as a steel knife.
- Streak: White.
- Habit: Orthorhombic crystal system.
Prehnite in different forms
Stones often confused with Prehnite
Frequently asked questions
How hard is Prehnite?
Prehnite is Mohs 6–6.5 on the hardness scale.
What colour is Prehnite?
Prehnite is typically green, yellow, clear, gray (Colorless to gray to yellow, yellow-green or white).