Dictionary:

topaz

  (tō'păz')

1. 1. A colorless, blue, yellow, brown, or pink aluminum silicate mineral, often found in association with granitic rocks and valued as a gemstone, especially in the brown and pink varieties.
   2. Any of various yellow gemstones, especially a yellow variety of sapphire or corundum.
2. A light yellow variety of quartz.
3. Either of two South American hummingbirds (Topaza pyra or T. pella) having colorful plumage.

[Middle English topace, from Old French, from Latin topazus, from Greek topazos.]

A mineral best known for its use as a gemstone. Crystals are usually colorless but may be red, yellow, green, blue, or brown. The wine-yellow variety is the one usually cut and most highly prized as a gem. Corundum of similar color sometimes goes under the name of Oriental topaz. Citrine, a yellow variety of quartz, is the most common substitute and may be sold as quartz topaz.

Topaz is a nesosilicate with chemical composition Al₂SiO₄(F,OH)₂. The mineral crystallizes in the orthorhombic system and is commonly found in well-developed prismatic crystals with pyramidal terminations. It has a perfect basal cleavage which enables it to be distinguished from minerals otherwise similar in appearance. Hardness is 8 on Mohs scale; specific gravity is 3.4–3.6. See also Hardness scales.

Fine yellow and blue crystals have come from Siberia and much of the wine-yellow gem material from Minas Gerais, Brazil. In the United States topaz has been found near Florissant, Colorado; in Thomas Range, Utah; in San Diego County, California; and near Topsham, Maine. See also Gem; Silicate minerals.

(click to enlarge)
Topaz from Minas Gerais state, Brazil (credit: Lee Boltin)

Aluminum silicate mineral, Al₂SiO₄(F,OH)₂, that is valued as a gemstone. It is formed by fluorine-bearing vapours given off during the last stages of the crystallization of igneous rocks. Pure topaz may be colourless and, when brilliant-cut, has been mistaken for diamond. It may also be various shades of yellow, blue, or brown. Imperial topaz, with vivid reddish orange colour, from Minas Gerais, Braz., is very highly valued.

For more information on topaz, visit Britannica.com.

Environment

In pegmatites, seams in granitic rock, high-temperature veins and replacement impregnations, and gas cavities in rhyolite.

Commonly crystallized, often in free-growing transparent crystals, sometimes very large. The c -face, the base, may be conspicuous or may be entirely missing; it is usually present. Also in parallel columnar growths (pycnite); in pseudomorphs after feldspar crystals; and in granular masses. When doubly terminated, "precious" (golden) crystals may appear hemimorphic, for the terminal faces at the two ends of the Brazilian precious topaz are usually unlike.

Colorless, white, pale blue, light yellow, yellow-brown, pinkish brown, pink, and ruby red. Luster glassy; hardness 8; specific gravity 3.5-3.6; fracture conchoidal; cleavage perfect basal. Transparent to translucent.

Aluminum fluohydroxysilicate (56.5% Al ₂ O ₃ , 33.3% SiO ₂ , and about 10% F and OH). The paragenetical habit differences are great enough to suggest major structural differences, perhaps related to the F and OH content.

Infusible, and insoluble in all but hydrofluoric acid. The powder turns blue (aluminum test) when moistened with cobalt nitrate and heated.

Great hardness and its good cleavage are excellent indications, along with its crystal form and typical occurrence and pegmatitic associations. Beryl fuses on thin edges; quartz decrepitates more violently and easily.

A valuable jewelry stone, especially in the pink, red, and brown hues. Not to be confused with the brown quartz commonly sold in Brazil and other lands (under the name topaz, as in "smoky topaz."

Large topaz crystals are not common in the U.S.; the biggest are probably some crudely shaped white ones found in the pegmatite at Amelia, Virginia, associated with microcline. Clear crystals, to 4-5 in. (10 cm) across and somewhat etched, from Devils Head and Pikes Peak, Colorado; smaller crystals have come from other Colorado localities. Large and deeply etched blue crystals were found at Topsham, Maine, and many 1-2 in. (2-5 cm) crystals were found in small miarolitic cavities in granite with smoky quartz, feldspar, and phenakite at Baldface Mountain, New Hampshire. Less etched, pale blue crystals are found in Mason Co., Texas. Also important in San Diego Co., California, dikes associated with beryl and tourmaline.

Rhyolite extrusions of the Thomas Range, Utah (and, less conspicuously, of Nathrop, Colorado, and New Mexico) contain many gas cavities in which there are 1-in. (3 cm) light brown crystals, which soon fade to colorless on exposure to light. Larger but sandy crystals within the rhyolite, mostly filled with quartz and opaque, are always simpler in their terminations. It is associated in Utah with black bixbyite ([Mn,F] ₂ O ₃ ) cubes, rosy beryl (not morganite), and in Colorado with spessartine garnet. In San Luis Potosí, Mexico, similar and sometimes larger topaz appears to occur alone or perhaps with cassiterite in the rhyolite seams.

Brazilian topaz is outstanding and comes in pegmatitic colorless and blue crystals, as well as in a series of quartz veins in rich brown gemmy crystals known as "precious topaz." Pink crystals of this type have also been found in nearby hematite mines and lately in Pakistan. Small natural pink Russian topazes from the valley of the Sanarka River resemble some of the brown Brazilian gemstones, with the same crystal habit. Fine blue topaz crystals (and sherry-hued fading to blue) were found years ago in pegmatites in the Ural Mountains; lately large numbers of pale brown crystals, fading to white, have been found in Pakistan.

Though like pegmatite crystals in habit, the small crystals cut for the Saxon crown jewels were straw-hued topazes from veins in and near the "Schneckenstein" (snail stone, from its shape) in the Erzgebirge near the Czechoslovakian border.

Golden Brazilian "precious" topaz turns pink on heating, and most pink jewelry topaz has been heated, though recent finds in Pakistan are naturally pink. Topaz is a very attractive and abundant species, characterized by beautiful crystals, placing it among the more popular gemstones with collectors. The common deep blue topaz now so abundant in the jewelry trade is largely irradiated white material; no naturally blue topaz ever reaches such a rich hue.

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

Topaz
an group of topaz crystals on matrix
General
Category	Mineral
Chemical formula	Al2SiO4(F,OH)2
Identification
Color	Clear (if no impurities), blue, brown, orange, gray, yellow, green, pink and reddish pink.
Crystal system	orthorhombic
Fracture	conchoidal
Mohs Scale hardness	8
Luster	Vitreous/glossy
Specific gravity	3.4–3.6

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al₂SiO₄(F,OH)₂. 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 also be 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 known to be 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. ^[1]. 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, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico, and the United States.

Topaz crystals from Brazilian pegmatites are up to 80 cm x 60 cm x 60 cm in size.^[2] The biggest topaz crystal ever found, named "El Dorado", was found in Brazil in 1984. It weighs 6.2 kg and belongs to the British Royal Collection. The famous Braganza diamond is in most likelihood a Topaz. The Topaz of Aurungzebe, observed by Jean Baptiste Tavernier measured 157.75 carats.^[3]

Etymology and historical and mythical usage

Colorless topaz, Minas Gerais, Brazil

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. ^[4] 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 tòpazi[òs], 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. ^[5] 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 (Blue Topaz for December), and the state gemstone for Utah.

References

Wikimedia Commons has media related to:

Topaz

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

1. ^ Several Books at the "Pink Topaz" section on Farlang: Fernie: Precious Stones for Curative Wear, London, 1907; Oliver Farrington: Gems and Gem Minerals, Chicago, 1903. Wodiska, A Book of Precious Stones, New York, 1910 (see external links)
2. ^ The Complete Encyclopedia of Minerals by P. Korbel and M. Novak
3. ^ Famous and Notheworthy Topazes Rao Bahadur, A Handbook of Precious Stones, Geological Survey of India
4. ^ Nicols who wrote one of the first systematic treatises on minerals and gemstones dedicated two chapters on the topic in 1652: A Lapidary or History of Gemstones, University of Cambridge, 1652
5. ^ see for extensive discussion Oliver Farrington, Gems and Gem Minerals, Chicago, 1903. Farrington was curator of Natural History Museum in Chicago.

External links

• Pink Topaz, Biblical Topaz References a few dozen full text historical references on Topaz
• Webmineral
• Mindat with location data
• Mineral galleries

Common jewellery materials
Precious metals:	Gold · Silver (Sterling silver) · Platinum · Palladium
Gemstones:	Diamonds · Rubies · Emeralds · Sapphires · Amethyst · Opals · Topaz · Aquamarine · Tanzanite · Alexandrite
Others:	Amber · Pearls

Gemstones and crystals
Gems:	Aquamarine · Emerald · Garnet · Jasper · Lapis lazuli · Pearl · Peridot · Ruby · Sunstone · Tiger's eye
Crystals:	Agate · Amethyst · Chalcedony · Diamond · Pyrite · Quartz · Rhodochrosite · Sapphire · Topaz · Tourmaline

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - topas

Nederlands (Dutch)
topaas

Français (French)
n. - topaze

Deutsch (German)
n. - Topas

Ελληνική (Greek)
n. - (ορυκτολ.) τοπάζι

Italiano (Italian)
topazio

Português (Portuguese)
n. - topázio (m)

Русский (Russian)
топаз

Español (Spanish)
n. - topacio

Svenska (Swedish)
n. - topas

中文（简体） (Chinese (Simplified))
黄晶, 南美蜂鸟, 黄玉

中文（繁體） (Chinese (Traditional))
n. - 黃晶, 南美蜂鳥, 黃玉

한국어 (Korean)
n. - 황옥, 벌새의 일종

日本語 (Japanese)
n. - 黄玉, トパーズ

العربيه (Arabic)
‏(الاسم) حجر كريم مختلف ألأشكال وألألوان, ألتوباز‏

עברית (Hebrew)
n. - ‮טופז, פטדה‬

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