Properties
| Category | Silicate mineral |
|---|---|
| Formula | Ca2Al(AlSi3O10)(OH)2 |
| Crystal system | Orthorhombic |
| Color | Colorless to gray to yellow, yellow-green or white |
| Crystal habit | Globular, reniform to stalactitic |
| Cleavage | Distinct on |
| Tenacity | Brittle |
| Mohs scale hardness | 6–6.5 |
| Luster | Vitreous to pearly |
| Streak | White |
| Diaphaneity | Semi-transparent to translucent |
| Specific gravity | 2.8–2.95 |
From the Wikipedia article
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 and China. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its hardness is 6.5, its specific gravity is 2.80–2.95 and its color varies from light green to yellow, but also colorless, blue, pink or white. In April 2000, rare orange prehnite was discovered in the Kalahari Manganese Fields, South Africa. Prehnite is mostly translucent, and rarely transparent.
Source
Source record: crystal-compendium/prehnite/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Prehnite — revision id 1375604209. Text and properties from Wikipedia, licensed CC BY-SA 4.0.