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 - or + |
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 |