Kyanite vs Staurolite
| Property | Kyanite | Staurolite |
|---|---|---|
| Formel | Al2SiO5 | Fe2Al9Si4O23(OH) |
| Kristallsystem | Triclinic | Monoclinic |
| Mineralklasse | 09 Silicates | 09 Silicates |
| Mohshärte | 4.5-7.0 | 7.0-7.5 |
| Farbe | Blue, white, gray, green | Dark reddish-brown to black |
| Glanz | Vitreous | Vitreous |
| Strichfarbe | Colorless | Gray to white |
| Transparenz | Translucent | Translucent |
| Spaltbarkeit | Perfect {100} | Poor {010} |
| Bruch | Splintery | Subconchoidal |
Key Differences
- ◆ Kyanite is known for variable hardness (4.5 along the crystal, 7 across); staurolite has a consistent 7–7.5.
- ◆ Staurolite is famous for cruciform twinned crystals (natural crosses); kyanite forms bladed columnar crystals.
- ◆ Both are metamorphic index minerals: kyanite indicates high pressure; staurolite indicates medium-grade metamorphism.
- ◆ Kyanite (Al2SiO5) is a polymorph of sillimanite and andalusite; staurolite is a distinct iron-aluminum silicate.
- ◆ Kyanite is typically blue; staurolite is dark reddish-brown to black.