Corundum
From The Gemology Project
Revision as of 08:48, 2 October 2006 by Africanuck (talk | contribs)
Corundum | |
---|---|
Chemical composition | Al2O3 |
Crystal system | Trigonal |
Habit | Prismatic, tabular |
Cleavage | None; twinned stones may show parting |
Fracture | Conchoidal |
Hardness | 9 |
Optic nature | Uniaxial - |
Refractive index | 1.762-1.770 (+.009,-.005) |
Birefringence | 0.008-0.010 |
Dispersion | Low, 0.018 |
Specific gravity | 4 |
Lustre | Vitreous to Subadamantine |
Pleochroism | Weak to moderate |