AskDefine | Define topaz

Dictionary Definition

topaz

Noun

1 a yellow quartz [syn: false topaz, common topaz]
2 a mineral (fluosilicate of aluminum) that occurs in crystals of various colors and is used as a gemstone
3 a light brown [syn: tan]

User Contributed Dictionary

English

Noun

topaz
  1. a clear, yellowish-brown gemstone.
  2. (colour) a yellowish-brown color, like that of the gemstone.
    topaz colour:   

Translations

gem
colour

Adjective

topaz
  1. of a yellowish-brown color, like that of the gemstone.

Translations

colour

Derived terms

Related terms

See also

Extensive Definition

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It is the birthstone of the month November. It crystallizes in the orthorhombic group 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, meaning that gemstones or other fine specimens have to 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 luster. Pure topaz is transparent but is usually tinted by impurities; typical topaz is wine or straw-yellow. They may be made white, gray, green, blue, pink or reddish-yellow and transparent or translucent.

Treatments

When heated, yellow topaz often becomes reddish-pink. The color change upon heating was first discovered by a Parisian jeweler around 1750. In particular the yellow topaz of Brazil has been treated frequently by wrapping topaz in asbestos. Only stones of a brown-yellow color yield the pink; the pale yellow ones usually turn white. The pink color is stable. . Topaz can also be irradiated, turning the stone blue, ranging from a light pure color to very dark almost electric blue. A recent trend in jewelry is the manufacture of topaz specimens that display iridescent colors, by applying a thin layer of titanium oxide via physical vapor deposition, this stone is then sold as 'mystic topaz'.

Localities and occurrence

Topaz is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite lava flows like those at Topaz Mountain in western Utah. It may be found with fluorite and cassiterite. It can be found in the Ural and Ilmen mountains, Afghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico, Flinders Island and the United States. Some clear topaz crystals from Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. Crystals of this size may be seen in museum collections. The famous Braganza diamond is in most likelihood a topaz. The Topaz of Aurungzebe, observed by Jean Baptiste Tavernier measured 157.75 carats.

Etymology and historical and mythical usage

The name "topaz" is derived from the Greek Τοπάζιος (Τοpáziοs), which was the ancient name of St. John's Island in the Red Sea which was difficult to find and from which a yellow stone (now believed to be chrysolite: yellowish olivine) was mined in ancient times; topaz itself (rather than topazios) wasn't really known about before the classical era. 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.
Many modern English translations of the Bible, including the King James Version mention topaz in Exodus 28:17 in reference to a stone in the Hoshen: "And thou shalt set in it settings of stones, even four rows of stones: the first row shall be a sardius, a topaz, and a carbuncle: this shall be the first row." However, since these translations as topaz all derive from the Septuagint translation topazi[os], which as mentioned above referred to a yellow stone that wasn't topaz, probably chrysolite, it should be borne in mind that topaz is not meant here. The masoretic text (the Hebrew on which most modern bible translations of the Old Testament are based) has pitdah as the gem the stone is made from; pitdah is of unknown meaning, though scholars think it is related to an Assyrian word meaning flashed. There is a wide range of views among traditional sources about which tribe of the Israelites the stone refers to.
Yellow topaz is the traditional November birthstone, and the state gemstone for the US State of Utah.

References

  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7

External links

topaz in Arabic: زبرجد
topaz in Bulgarian: Топаз
topaz in Czech: Topaz
topaz in Danish: Topas
topaz in German: Topas
topaz in Estonian: Topaas
topaz in Spanish: Topacio
topaz in Basque: Topazio
topaz in Persian: زبرجد هندی
topaz in French: Topaze (minéral)
topaz in Korean: 황옥
topaz in Croatian: Topaz
topaz in Italian: Topazio
topaz in Hebrew: טופז
topaz in Lithuanian: Topazas
topaz in Hungarian: Topáz
topaz in Dutch: Topaas
topaz in Japanese: トパーズ
topaz in Norwegian: Topas
topaz in Polish: Topaz
topaz in Portuguese: Topázio
topaz in Romanian: Topaz
topaz in Quechua: Q'illu umiña
topaz in Russian: Топаз
topaz in Simple English: Topaz
topaz in Slovak: Topás
topaz in Slovenian: Topaz
topaz in Finnish: Topaasi
topaz in Swedish: Topas
topaz in Turkish: Topaz
topaz in Ukrainian: Топаз
topaz in Chinese: 黄玉
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