Corundum vs Tourmaline
| Property | Corundum | Tourmaline |
|---|---|---|
| Formula | Al2O3 | Complex borosilicate |
| Crystal System | Trigonal | Trigonal |
| Mineral Class | 04 Oxides and Hydroxides | 09 Silicates |
| Mohs Hardness | 9.0 | 7.0-7.5 |
| Color | Red (ruby), blue (sapphire), various colors | Black, green, pink, blue, watermelon |
| Luster | Adamantine | Vitreous |
| Streak | Colorless | Colorless |
| Transparency | Transparent | Transparent |
| Cleavage | None | None |
| Fracture | Conchoidal to uneven | Conchoidal to uneven |