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>> Group(s) : silicates
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Described by Breithaupt in 1823, its name comes from the Greek Greek "orthos" meaning “straight fracture“, because it has the characteristic to cleave in two orthogonal planes. Named at the beginning orthoclase, orthose, its french name, was given lately by René Just Haüy.
In its white variety adularia, which name comes from the Latin word "Adula" which was the name of Mount St Gothard in Switzerland where it was commonly found, it is a constituent of the moonstone. The adularia is actually a microperthite, a result of the demixing of microscopic platelets of albite in the orthoclase during the cooling of the mixture of orthoclase and albite.
The adularescence phenomenon, which is the apparition of bluish reflets, is due to the interference created by these micro-plates of albite in the orthoclase forming a real grating diffraction.
The sanidine is a light color variety (colorless, light brown), discovered by Nose in Germany in 1808, its name comes from the Greek "Sanis" which means “ in small plates “ and "Idos" for “ to see “, summarizing the appearance of its crystals.
It is the standard hardness number 6 on the Mohs scale of hardness which goes from 1 to 10 .

Exploited sites

Common feldspar, is found in Madagascar, Burma, Kenya, Mozambique, Rwanda, Namibia, Bolivia, India, Pakistan, China, Russia, Greece, Slovakia, Switzerland, France , England, North America, Australia

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Use in jewelry

It is used for emerald cuts type, or grading cut when the yellow color is quite strong.

Daily care and precautions

Beautiful stone fairly easy to maintain, of medium hardness and therefore susceptible to scratches. It is washed with water and washing up liquid, rinse with water without lime and then with alcohol.

Looking alike stones

apatite , beryl , brazilianite , chrysoberyl , citrine , scapolite , topaz , zircon

Historical healing properties

As one of the constituents of the moonstone, it has some of its properties, it would be a smooth stone suitable for people too materialistic and rational, she would bring imagination, tolerance and sensitivity.

Chemical characteristics

potassium aluminum silicate

Physical characteristics

Main color : yellow

Other colors : brown, grey, colourless, pink, red, green

Color of streak : white

Luster : vitreous

Hardness : 6.0

Density : 2.55 to 2.65

Cleavage : perfect

Optical properties

Transparency : transparent

Refractive Index : 1.518 - 1.530

Double refraction : 0.008

Very weak, biaxial (-)

visible double refraction : no

Dispersion : 0,012 (0.008)

Pleochroism : very weak

Number of colors : 2

Colorless, yellow

Fluorescence : variable

Orange - pink


Prismatic massive, often twinned for sanidine


Crystal system : monoclinic

Other informations
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