| Chemical Formula | Al2O3∙nH2O (aluminum oxide and water) |
| Color | Various shades of red, brown, yellow, or gray |
| Streak | White |
| Luster | Dull to earthy |
| Hardness | 1-3 on the Mohs scale |
| Specific Gravity | 2.2 - 2.5 |
| Cleavage | None |
| Fracture | Irregular |
| Transparency | Translucent to opaque |
| Crystal System | Amorphous (non-crystalline) |
| Habit | Botryoidal, oolitic, or massive |
| Density | 2.55 - 3.25 g/cm³ |
| Melting Point | Approximately 2,050°C (3,722°F) |
