Properties
| Category | Nesosilicate |
|---|---|
| Formula | Al2SiO5 |
| Crystal system | Orthorhombic |
| Color | Colourless or white to grey, also brown, yellow, yellow-green, grey-green, blue-green, blue; colourless in thin section |
| Crystal habit | Prismatic crystals, fibrous, acicular |
| Cleavage | {010} perfect |
| Fracture | Splintery |
| Tenacity | Tough |
| Mohs scale hardness | 7 |
| Luster | Vitreous to subadamantine, silky |
| Streak | White |
| Diaphaneity | Transparent to translucent |
| Specific gravity | 3.24 |
From the Wikipedia article
Sillimanite or fibrolite is an aluminosilicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman (1779–1864). It was first described in 1824 for an occurrence in Chester, Connecticut.
Source
Source record: crystal-compendium/sillimanite/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Sillimanite — revision id 1223083680. Text and properties from Wikipedia, licensed CC BY-SA 4.0.