Difference between revisions of "Template:Feldspar"

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| Refractive index || 1.52 - 1.53 (K-feldspar)<br />
 
| Refractive index || 1.52 - 1.53 (K-feldspar)<br />
1.52 - 1.57 (plagioclase)  
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1.528 - 1.588 (plagioclase)  
 
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|-  
 
| Birefringence || 0.006 - 0.007 (K-feldspar)<br />
 
| Birefringence || 0.006 - 0.007 (K-feldspar)<br />

Latest revision as of 09:48, 8 March 2009

Feldspar
Chemical composition Potassium, sodium and calcium-aluminum 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 ±
Refractive index 1.52 - 1.53 (K-feldspar)

1.528 - 1.588 (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