Diaspore
From The Gemology Project
Diaspore | |
---|---|
Chemical composition | AlO(OH) |
Crystal system | Orthorhombic |
Habit | Tabular, sometimes fibrous |
Cleavage | Perfect to imperfect |
Fracture | Conchoidal |
Luster | Bright vitreous to pearly (on cleavage surface). |
Hardness | 6.5 - 7 |
Optic nature | Biaxial + |
Refractive index | 1.682 - 1.752 |
Birefringence | 0.040 - 0.048 |
Specific gravity | 3.2 - 3.5 |
Lustre | Vitreous |
Pleochroism | Moderate |
Diaspore as a plausible gemstone has been reported first around 1977 when a large enough crystal was examined at the Gem Testing Laboratory in London. This, usually colorless, material showed good color-change from pale bluish-green to pale pinkish-brown. Turkey was the origin of this color-change material.
When Zultanite Gems LLC aquired the mining location, this color-change variety of diaspore was marketed under the tradename "zultanite®". At present (2007) sole distribution rights of "zultanite®" are granted to GemsTV.