Difference between revisions of "Template:Feldspar"

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! colspan=2 | Feldspar
 
! colspan=2 | Feldspar
 
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| Chemical composition || Potassium, sodium and calcium-aluminium silicates<br />
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| Chemical composition || Potassium, sodium and calcium-aluminum silicates<br />
 
I. K-feldspar (KALSi<sub>3</sub>0<sub>8</sub>)<br />
 
I. K-feldspar (KALSi<sub>3</sub>0<sub>8</sub>)<br />
 
II . Plagioclase feldspar (isomorphous)
 
II . Plagioclase feldspar (isomorphous)

Revision as of 16:23, 23 December 2006

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)

1.52 - 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