Biotite vs Kyanite
| Property | Biotite | Kyanite |
|---|---|---|
| Formula | K(Mg,Fe)3(AlSi3O10)(OH)2 | Al2SiO5 |
| Crystal System | Monoclinic | Triclinic |
| Mineral Class | 09 Silicates | 09 Silicates |
| Mohs Hardness | 2.5-3.0 | 4.5-7.0 |
| Color | Black, dark brown, dark green | Blue, white, gray, green |
| Luster | Vitreous | Vitreous |
| Streak | White to gray | Colorless |
| Transparency | Translucent | Translucent |
| Cleavage | Perfect basal {001} | Perfect {100} |
| Fracture | Uneven | Splintery |