Kyanite
| Colour | Blue, White, Green, Gray |
|---|---|
| Mohs hardness | 4.5–5 parallel to one axis 6.5–7 perpendicular to that axis |
| Lustre | Vitreous to white |
| Streak | White |
| Crystal system | Triclinic |
| Transparency | Transparent to translucent |
| Cleavage | [100] perfect [010] imperfect with 79° angle between |
| Fracture | Splintery |
| Specific gravity | 3.53–3.65 measured; 3.67 calculated |
What is Kyanite?
Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust. Kyanite is also known as disthene or cyanite.
How to identify Kyanite
- Lustre: Vitreous to white.
- Hardness: Mohs 4.5–5 parallel to one axis 6.5–7 perpendicular to that axis — soft; a knife will scratch it.
- Streak: White.
- Habit: Triclinic crystal system.
Kyanite in different forms
Stones often confused with Kyanite
Frequently asked questions
How hard is Kyanite?
Kyanite is Mohs 4.5–5 parallel to one axis 6.5–7 perpendicular to that axis on the hardness scale.
What colour is Kyanite?
Kyanite is typically blue, white, green, gray (Blue, white, rarely green, light gray to gray, rarely yellow, pink, orange, and black, can be zoned).