Topaz

This article is about the mineral or gemstone, for other uses see: Topaz (disambiguation).

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The mineral topaz is a silicate of aluminium and fluorine with the chemical formula (AlF)2SiO4. It is orthorhombic and its crystals are mostly prismatic terminated by pyramidal and other faces, the basal pinacoid often being present. It has an easy and perfect basal cleavage and so gemstones or other fine specimens should be handled with care to avoid developing cleavage flaws. The fracture is conchoidal to uneven. Topaz has a hardness of 8, a specific gravity of 3.4-3.6, and a vitreous lustre. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow. They may also be white, gray, green, blue, or reddish-yellow and transparent or translucent. When heated, yellow topaz often becomes reddish-pink. It can also be irradiated, turning the stone a light and distinctive shade of blue. Mystic Topaz™ is manufactured by Azotic Coating Technology, Inc., a laboratory that deposits a thin layer of titanium oxide (via physical vapor deposition) on natural topaz which results in optical interference patterns that showcase a rainbow of colors.

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Topaz is found associated with the more acid rocks of the granite and rhyolite type and may be found with fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Czech Republic, Saxony, Norway, Sweden, Japan, Brazil, Mexico, and the United States.

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The name "topaz" is derived from the Greek topazos, "to seek," which was the name of an island in the Red Sea that was difficult to find and from which a yellow stone (now believed to be a yellowish olivine) was mined in ancient times. In the Middle Ages the name topaz was used to refer to any yellow gemstone, but now the name is only properly applied to the silicate described above.

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Topaz is also the birthstone of November.

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• See also: List of minerals

Mineral: This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band)....

Silicate: In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. It is also used to denote the salts of silica or of one of the silicic acids....

Aluminium: x...

Topaz related Images and Photos (experimental)

Topaz	Topaz I	Topaz II	Topaz DVD (Widescreen)
Topaz Sky I	Topaz Sky II	Topaz 1969	Topaz 1969
Heart Of Topaz