Difference between revisions of "Template:Feldspar"
From The Gemology Project
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! colspan=2 | Feldspar | ! colspan=2 | Feldspar | ||
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− | | Chemical composition || Potassium, sodium and calcium- | + | | 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 17:23, 23 December 2006
Feldspar | |
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Chemical composition | Potassium, sodium and calcium-aluminum 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 |