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Orthoclase (Feldspar)

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  More Information:

KAlSi₃O₈
Silicates: Tectosilicates
8/J.06-40 (Feldspar group)
(Buddingtonite - Slawsonite series)
Monoclinic - Prismatic
Vitreous to pearly
6.0 - 6.5
2.55 - 2.63
0.012 (low)
1.518 - 1.539  Biaxial ( - )
0.005 - 0.006
Barely Detectable, GRapi = 200.97
1823
Mindat.org
Webmineral.com
 

Orthoclase is a rare member of the Potassium Feldspars of the Feldspar Group of minerals that also includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Orthoclase is found at many localities thoughout the world but gem quality crystals are somewhat rare. Currently, the best know source may be Itrongahy, Madagascar. Orthoclase is a beautiful gem available in colorless and shades of champagne. It is also available in catseye gems.

The name Orthoclase is from the Greek words orthos meaning right and kalo meaning I cleave because its cleavages are at right angles. The name Feldspar is from the Swedish feldt + spat meaning that it was found in fields overlying granite.
 

We have not photographed our Orthoclase gems yet.  Please check back soon!