tridymite

/trid"euh muyt'/, n. Mineral.
a polymorph of quartz occurring in the form of small crystals, commonly twinned, in siliceous volcanic rocks.
[1865-70; < G Tridymit, equiv. to tridym- (Gk trídym(os) triple, equiv. to tri- TRI- + ()dymos DIDYMOUS) + -it -ITE1]

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       Properties of selected silica mineralssilica mineral, the stable form of silica (silicon dioxide, SiO2) at temperatures between 870° and 1,470° C (1,598° and 2,678° F); at lower temperatures it transforms to high-quartz, at higher to cristobalite. It has three modifications: high-tridymite, middle-tridymite, and low-tridymite. Tridymite forms thin hexagonal plates that are generally twinned, often in groups of three; its name alludes to this habit. It commonly occurs in igneous rocks, more abundantly than cristobalite, as in the trachytes of Rhineland-Palatinate, Germany; northern Italy; and in the Massif Central, France. Tridymite, also found in meteorites, has the same chemical composition as coesite, cristobalite, stishovite, lechatelierite, and quartz but has a different crystal structure. For detailed physical properties, see silica mineral (Table 2 (Properties of selected silica minerals)).

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Universalium. 2010.

Look at other dictionaries:

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  • Tridymite — is a high temperature polymorph of quartz and usually occurs as minute tabular white or colorless pseudo hexagonal triclinic crystals, or scales, in cavities in acidic volcanic rocks. Its chemical formula is SiO2. Tridymite is stable between 870… …   Wikipedia

  • Tridymite — Trid y*mite, n. [Gr. ? threefold. So called in allusion to the supposed threefold nature of the twin crystals.] (Min.) Pure silica, like quartz, but crystallizing in hexagonal tables. It is found in trachyte and similar rocks. [1913 Webster] …   The Collaborative International Dictionary of English

  • tridymite — ● tridymite nom féminin Silice cristallisée dans le système orthorhombique, pseudohexagonale, que l on trouve dans certaines roches volcaniques …   Encyclopédie Universelle

  • tridymite — noun A rare mineral of volcanic rocks that solidified at a high temperature, with the chemical composition silicon dioxide, SiO. Tridymite is chemically identical to quartz, but has a different crystal structure. Sometimes contains sodium… …   Wiktionary

  • tridymite — tridimitas statusas T sritis chemija apibrėžtis Polimorfinė SiO₂ atmaina. atitikmenys: angl. tridymite rus. тридимит …   Chemijos terminų aiškinamasis žodynas

  • tridymite — A form of silica used in dental casting investment. [fr. G. tridymos, threefold] …   Medical dictionary

  • tridymite — [ trɪdɪmʌɪt] noun a high temperature form of quartz found as thin hexagonal crystals in some igneous rocks and stony meteorites. Origin C19: from Ger. Tridymit, from Gk tridumos threefold , because it occurs in groups of three crystals …   English new terms dictionary

  • tridymite — trid·y·mite …   English syllables

  • tridymite — n. a crystallized form of silica, occurring in cavities of volcanic rocks. Etymology: G Tridymit f. Gk tridumos threefold (as TRI , didumos twin), from its occurrence in groups of three crystals …   Useful english dictionary

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