Template:Feldspar
From The Gemology Project
Feldspar | |
---|---|
Chemical composition | Potassium, sodium and calcium-aluminium silicates I. K-feldspar (KALSi308) |
Crystal system | Monoclinic - triclinic |
Habit | Prismatic, often twinned |
Cleavage | Good to perfect |
Fracture | Conchoidal |
Hardness | 6 |
Optic nature | Biaxial ± |
Refractive index | 1.52 - 1.53 (K-feldspar) 1.52 - 1.57 (plagioclase) |
Birefringence | 0.006 - 0.007 (K-feldspar) 0.008 - 0.011 (plagioclase) |
Specific gravity | 2.55 - 2,58 (K-feldspar) 2.60 - 2.80 (plagioclase) |
Lustre | Vitreous |