Staurolite
| Colour | Brown, Red, Black, Yellow |
|---|---|
| Mohs hardness | 7 – 7.5 |
| Lustre | Subvitreous to resinous |
| Streak | White to grayish |
| Crystal system | Monoclinic |
| Transparency | Transparent to opaque |
| Cleavage | Distinct on {010} |
| Fracture | Subconchoidal |
| Chemical formula | Fe 2+ 2 Al 9 O 6 (SiO 4 ) 4 (O,OH) 2 |
| Specific gravity | 3.74 – 3.83 meas. 3.686 calc |
What is Staurolite?
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.
How to identify Staurolite
- Lustre: Subvitreous to resinous.
- Hardness: Mohs 7 – 7.5 — hard enough to scratch glass.
- Streak: White to grayish.
- Habit: Monoclinic crystal system.
Staurolite in different forms
Stones often confused with Staurolite
Frequently asked questions
How hard is Staurolite?
Staurolite is Mohs 7 – 7.5 on the hardness scale.
What colour is Staurolite?
Staurolite is typically brown, red, black, yellow (Dark reddish brown to blackish brown, yellowish brown, rarely blue; pale golden yellow in thin section).