Template:Tourmaline
From The Gemology Project
Tourmaline | |
---|---|
Chemical composition | Complex borosilicate |
Crystal system | Trigonal |
Habit | Trigonal prisms with convex faces |
Fracture | Conchoidal |
Hardness | 7.5 |
Optic nature | Uniaxial - |
Refractive index | 1.62 - 1.64 |
Birefringence | 0.014-0.021 (up to 0.039) |
Dispersion | Low, 0.018 |
Specific gravity | 3.06 (3.01-3.11) |
Lustre | Vitreous |
Pleochroism | Weak to strong |