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>> Group(s) : feldspars, silicates
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Discovered on the Vesuvius (Italy) in 1823 by the mineralogist Rose, its name comes from the Greek "not straight" in relation to its triclinic crystals.
It is the calcium end member of the albite-anorthite series of the family of plagioclase feldspar.

Exploited sites

It is found worldwide, in France at Lassur (Ariege), in the Aveyron, at Tarqmiye in Palestine, in the Taurus Mountains in Turkey, Lybia, Madagascar, Brazil ...

See pictures of the mines / other pictures

Use in jewelry

in its most colorful varieties it is faceted cut , it is a collection stone.

Looking alike stones

calcite , dolomite , herderite , kunzite , magnesite , orthoclase , pollucite , sillimanite

Chemical characteristics

alumino-calcium silicate

Physical characteristics

Main color : colourless

Other colors : yellow, pink

Color of streak : white

Luster : vitreous

Hardness : 6.0 to 6.5

Density : 2.75 to 2.77

Cleavage : perfect

Fracture : uneven

some very tiny parts can be observed on the fracture, easy cleavage on a single side

Optical properties

Transparency : transparent, translucent

Refractive Index : 1.578 - 1.590

Double refraction : 0.013

Weak biaxial (-)

visible double refraction : no

Pleochroism : absent

Number of colors : 1

Fluorescence : none




Crystal system : triclinic

Other informations
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