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Sunstone is a gem variety of oligoclase feldspar. Oligoclase is a variety of plagioclase feldspar, which is itself an isomorphous mixture of albite (sodium aluminium silicate) and anorthite (calcium aluminium silicate).
In common with other feldspar gems, it displays a schiller of coloured light, caused by inclusions or its crystal structure creating interference effects of light.

Sunstone is a rich golden or reddish brown colour, with plays of red yellow and orange light, sometimes also with green, caused by the inclusion of microscopically thin plates of goethite or hematite.

Chemical Composition and NameNaAlSi3O8 - Sodium Aluminium Silicate
& CaAl2Si2O8 - Calcium Aluminium Silicate
Hardness6 - 6.5
Specific Gravity2.62 - 2.65
Crystalline SystemTriclinic
Refractive Index1.54 - 1.55
Optic SignPositive
Optical CharacterBiaxial the Lowest Possible Price

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