Properties
| Category | Nesosilicate |
|---|---|
| Formula | Fe2+2Al9O6(SiO4)4(O,OH)2 |
| Crystal system | Monoclinic |
| Color | Dark reddish brown to blackish brown, yellowish brown, rarely blue; pale golden yellow in thin section |
| Crystal habit | Commonly in prismatic crystals |
| Cleavage | Distinct on {010} |
| Fracture | Subconchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 7 – 7.5 |
| Luster | Subvitreous to resinous |
| Streak | White to grayish |
| Diaphaneity | Transparent to opaque |
| Specific gravity | 3.74 – 3.83 meas. 3.686 calc. |
From the Wikipedia article
Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and the chemical formula: Fe2+2Al9O6(SiO4)4(O,OH)2. Magnesium, zinc and manganese substitute in the iron site and trivalent iron can substitute for aluminium.
Source
Source record: crystal-compendium/staurolite/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Staurolite — revision id 1320254274. Text and properties from Wikipedia, licensed CC BY-SA 4.0.