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Oligoclase (Feldspar)

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  More Information:

(Na,Ca)(Si,Al)₄O₈
Silicates: Tectosilicates
8/J.07-30 (Feldspar group)
(Anorthoclase - Banalcite series)
Triclinic - Pinacoidal
Vitreous to pearly
7.0
2.62 - 2.67
0.012
1.542 - 1.549  Biaxial ( - )
0.007
1826
Mindat.org
Webmineral.com
 

Oligoclase is a rare member of the Plagioclase Feldspars of the Feldspar Group of minerals that also includes Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone. Oligoclase is found as colorless to pale green crystals in only a few locations around the world.

The name Oligoclase is from the Greek words meaning little break because the cleavage was believed to be less perfect than Albite. Plagioclase is from the Greek meaning oblique cleavage. Feldspar is from the Swedish feldt + spat meaning that it was found in fields overlying granite.
 

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