Oligoclase

Oligoclase ( gr ὀλίγος oligos for " little " and κλάσις classified for " breaking ") is a very common variety of the mineral albite from the mixed batch of plagioclase, group of the feldspars and the mineral class of framework silicates with the chemical formula (Na, Ca) Al (Si, Al) 3o8. It crystallizes in the triclinic crystal system with different colors depending on the variety (white, yellow, red, green, multicolored ).

Varieties and modifications

• Aventurine feldspar or sunstone has reddish- brownish color and glitters strongly by microcrystalline inclusions of hematite and other iron oxides. He is often confused with aventurine quartz and imitated by Goldstone.

Education and Locations

Oligoclase is a typical, rock-forming solid solution with the composition AN10 - AN30 ( albite with a content of 10 to 30% anorthite ) and either forms magmatic granite, syenite, andesite or pegmatite or in metamorphic gneiss and migmatite.

As localities are especially Ontario in Canada, Oregon in the USA, and Tvedestand Arendal in Norway, the Urals in the Russian Federation, Badajoz in Spain and in the Czech Republic Věžná mentioned.

Use

The variety Sunstone is processed into semi-precious stones. It comes as before in India, Norway, South Africa and the U.S. and is often imitated. The most common imitation, called Gold River, Goldstein or Aventuringlas is a glass in which copper or hematite was melted in microcrystalline form. This procedure was practiced in the 17th century by Venetian glass manufacturers.