| Property |
Specification |
| Chemical Formula |
Al₂O₃ (Aluminum Oxide) with Cr impurities |
| Crystal System |
Trigonal (Hexagonal) |
| Crystal Habit |
Tabular, prismatic, or granular crystals |
| Color |
Deep red to pinkish red |
| Streak |
White |
| Luster |
Vitreous to subadamantine |
| Transparency |
Transparent to translucent |
| Hardness (Mohs scale) |
9 |
| Specific Gravity |
3.97 - 4.05 |
| Cleavage |
None (poor) |
| Fracture |
Conchoidal to uneven |
| Refractive Index |
1.762 - 1.770 |
| Birefringence |
0.008 - 0.010 |
| Optical Properties |
Uniaxial (-) |
| Pleochroism |
Strong (red to purplish-red) |
| Melting Point |
~2,050 °C |
