topaz

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topaz A nesosilicate mineral, Al2SiO4(OH,F)2; sp. gr. 3.5–3.6; hardness 8; orthorhombic; colourless, pale yellow, pale blue, yellowish, or sometimes pink; often transparent; vitreous lustre; crystals are prismatic and often bipyramidal with the vertical faces striated, but it can also be massive and granular; cleavage perfect basal orthorhombic; typically occurs in granite pegmatites, rhyolite, and quartz veins, and extensively as an accessory mineral in granites, associated with fluorite, tourmaline, beryl, and cassiterite, also in alluvial deposits. It is associated with pneumatolytic action (see PNEUMATOLYSIS) and is a constituent of greisen. The original cairngorms (see QUARTZ) were topaz crystals. It is named after Topazos Island in the Red Sea.

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topaz (tō´păz), aluminum silicate mineral with either hydroxyl radicals or fluorine, Al2SiO4(F,OH)2, used as a gem. It is commonly colorless or some shade of pale yellow to wine-yellow; pale blue and pale green also occur, but natural red stones are uncommon. Some natural yellow stones lose their yellow coloring when heated and become permanently pink ( "pinked" topaz). The stone is transparent with a vitreous luster. It has perfect cleavage on the basal pinacoid, but it is nevertheless hard and durable. The brilliant cut is commonly used. Topaz crystals, which are of the orthorhombic system, occur in highly acid igneous rocks, e.g., granites and rhyolites, and in metamorphic rocks, e.g., gneisses and schists. Important sources of topaz are in Russia, Siberia, Brazil, Australia, and Mexico and in New Hampshire, Colorado, and Utah in the United States. The name topaz is commonly but incorrectly used for various other yellow stones, e.g., for citrine quartz.

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to·paz / ˈtōpaz/ • n. 1. a precious stone, typically colorless, yellow, or pale blue, consisting of a fluorine-containing aluminum silicate. ∎  a dark yellow color. 2. a large tropical American hummingbird (genus Topaza) with a yellowish throat and a long tail.

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Topaz ★★★ 1969 (PG)

American CIA agent and French intelligence agent combine forces to find information about Russian espionage in Cuba. Cerebral and intriguing, but not classic Hitchcock. Based on the novel by Leon Uris. 126m/C VHS, DVD . John Forsythe, Frederick Stafford, Philippe Noiret, Karin Dor, Michel Piccoli; D: Alfred Hitchcock; W: Samuel A. Taylor; C: Jack Hildyard; M: Maurice Jarre. Natl. Bd. of Review ‘69: Director (Hitchcock), Support. Actor (Noiret).

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topaz Transparent, glassy mineral, aluminium fluosilicate, Al2SiO4(F,OH)2, found in pegmatites. Its crystals are orthorhombic system columnar prisms. Topaz is colourless, white, blue or yellow; some large crystals are of gem quality. Hardness 8; r.d. 3.5.

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topaz precious stone. XIII. ME. topace — OF, topace, (also mod.) topaze — L. topaz(i)us, -ion — Gr. tópazos, -ázion.

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topazAbkhaz, as, Baz, has, jazz, pizzazz, razz, whereas •Boas, Boaz •topaz • Shiraz • Alcatraz • razzmatazz