Difference between revisions of "Template:Feldspar"

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| Hardness || 6
 
| Hardness || 6
 
|-
 
|-
| Optic nature || biaxial -
+
| Optic nature || biaxial - or +
 
|-
 
|-
 
| Refractive index || 1.52 - 1.53 (K-Feldspar)<br />
 
| Refractive index || 1.52 - 1.53 (K-Feldspar)<br />

Revision as of 14:15, 22 November 2006

Feldspar
Chemical composition Potassium, Sodium and Calcium-Aluminium Silicates

I. K-Feldspar (KALSi308)
II . Plagioclase Feldspar (isomorphous)

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