Physical Properties |
|
| Chemical formula | Al2O3 |
| Class | Oxide |
| Crystal system | Hexagonal (rhombohedral) |
| Habit | Hexagonal Tabular Prismatic Massive Granular Euhedral crystals are rare. |
| Color | Brown Blue Pink Red (ruby) Green Yellow Multicolored |
| Hardness | 9 |
| Specific gravity | 3.9 to 4.1 |
| Cleavage | None |
| Fracture | Uneven Rectangular parting |
| Luster | Adamantine Vitreous |
| Transparency | Transparent to translucent |
| Streak | White |
Optical Properties |
|
| PPL | Typically colorless May be pale pink, blue, green, or yellow Extremely high relief |
| XPL | 1st order grays/yellows |
| δ | 0.008 |
| after Perkins, 371-372 |
Corundum in Hand Sample
Corundum
Hexagonal corundum
Pinkish red corundum (ruby) with black hornblende in the epidote-family mineral zoisite
Corundum in Thin Section
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