Oligoclase
| Colour | White, Gray, Clear |
|---|---|
| Mohs hardness | 6 to 6.5 |
| Lustre | Vitreous |
| Streak | White |
| Crystal system | Triclinic |
| Cleavage | Perfect {001}, Good {010}, Poor {110} |
| Fracture | Uneven, sub-conchoidal |
| Chemical formula | (Ca,Na)(Al,Si) 4 O 8 (Na:Ca = 70:30 to 90:10) |
| Specific gravity | 2.64 to 2.66 |
What is Oligoclase?
Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite (NaAlSi3O8) and anorthite (CaAl2Si2O8). The albite:anorthite molar ratio of oligoclase ranges from 90:10 to 70:30.
How to identify Oligoclase
- Lustre: Vitreous.
- Hardness: Mohs 6 to 6.5 — about as hard as a steel knife.
- Streak: White.
- Habit: Triclinic crystal system.
Oligoclase in different forms
Stones often confused with Oligoclase
Frequently asked questions
How hard is Oligoclase?
Oligoclase is Mohs 6 to 6.5 on the hardness scale.
What colour is Oligoclase?
Oligoclase is typically white, gray, clear (Usually white, with shades of grey, green, or red).