quartz


quartz
quartzose /kwawrt"sohs/, quartzous /kwawrt"seuhs/, adj.
/kwawrts/, n.
one of the commonest minerals, silicon dioxide, SiO2, having many varieties that differ in color, luster, etc., and occurring either in masses (as agate, bloodstone, chalcedony, jasper, etc.) or in crystals (as rock crystal, amethyst, citrine, etc.): the chief constituent of sand and sandstone, and an important constituent of many other rocks. It is piezoelectric and used to control the frequencies of radio transmitters.
[1750-60; < G Quarz]

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Second most abundant mineral (after feldspar) in the Earth's crust, present in many rocks.

Quartz, which consists of silica, or silicon dioxide (SiO2), has great economic importance. Many varieties are gemstones, including amethyst, citrine, smoky quartz, and rose quartz. Sandstone, composed mainly of quartz, is an important building stone. Large amounts of quartz sand (or silica sand) are used in the manufacture of glass and ceramics and for molds in metal casting. Crushed quartz is used as an abrasive in sandpaper; silica sand is employed in sandblasting; and sandstone is used whole to make whetstones, millstones, and grindstones. Silica glass (or fused quartz) is used in optics to transmit ultraviolet light. Tubing and various vessels of fused quartz have important laboratory applications, and quartz fibres are employed in extremely sensitive weighing devices.

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 widely distributed mineral of many varieties that consists primarily of silica, or silicon dioxide (SiO2). Minor impurities such as lithium, sodium, potassium, and titanium may be present. Quartz has attracted attention from the earliest times; water-clear crystals were known to the ancient Greeks as krystallos—hence the name crystal, or more commonly rock crystal, applied to this variety. The name quartz is an old German word of uncertain origin first used by Georgius Agricola (Agricola, Georgius) in 1530.

      A brief treatment of quartz follows. For full treatment, see silica mineral.

 Quartz has great economic importance. Many varieties are gemstones, including amethyst, citrine, smoky quartz, and rose quartz. sandstone, composed mainly of quartz, is an important building stone. Large amounts of quartz sand (also known as silica sand) are used in the manufacture of glass and ceramics and for foundry molds in metal casting. Crushed quartz is used as an abrasive in sandpaper, silica sand is employed in sandblasting, and sandstone is still used whole to make whetstones, millstones, and grindstones. Silica glass (also called fused quartz) is used in optics to transmit ultraviolet light. Tubing and various vessels of fused quartz have important laboratory applications, and quartz fibres are employed in extremely sensitive weighing devices.

      Quartz is the second most abundant mineral in the Earth's crust after feldspar. It occurs in nearly all acid igneous, metamorphic, and sedimentary rocks. It is an essential mineral in such silica-rich felsic rocks as granites, granodiorites, and rhyolites. It is highly resistant to weathering and tends to concentrate in sandstones and other detrital rocks. Secondary quartz serves as a cement in sedimentary rocks of this kind, forming overgrowths on detrital grains. Microcrystalline varieties of silica known as chert, flint, agate, and jasper consist of a fine network of quartz. Metamorphism of quartz-bearing igneous and sedimentary rocks typically increases the amount of quartz and its grain size.

      Quartz exists in two forms: (1) alpha-, or low, quartz, which is stable up to 573° C (1,063° F), and (2) beta-, or high, quartz, stable above 573° C. The two are closely related, with only small movements of their constituent atoms during the alpha-beta transition. The structure of beta-quartz is hexagonal, with either a left- or right-handed symmetry group equally populated in crystals. The structure of alpha-quartz is trigonal, again with either a right- or left-handed symmetry group. At the transition temperature the tetrahedral framework of beta-quartz twists, resulting in the symmetry of alpha-quartz; atoms move from special space group positions to more general positions. At temperatures above 867° C (1,593° F), beta-quartz changes into tridymite, but the transformation is very slow because bond breaking takes place to form a more open structure. At very high pressures alpha-quartz transforms into coesite and, at still higher pressures, stishovite. Such phases have been observed in impact craters.

      Quartz is piezoelectric: a crystal develops positive and negative charges on alternate prism edges when it is subjected to pressure or tension. The charges are proportional to the change in pressure. Because of its piezoelectric property, a quartz plate can be used as a pressure gauge, as in depth-sounding apparatus.

      Just as compression and tension produce opposite charges, the converse effect is that alternating opposite charges will cause alternating expansion and contraction. A section cut from a quartz crystal with definite orientation and dimensions has a natural frequency of this expansion and contraction (i.e., vibration) that is very high, measured in millions of vibrations per second. Properly cut plates of quartz are used for frequency control in radios, televisions, and other electronic communications equipment and for crystal-controlled clocks and watches.

 For detailed physical properties, see silica mineral (table—>).
 

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Universalium. 2010.

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  • quartz — [ kwarts ] n. m. • 1749; all. Quarz ♦ Forme cristalline commune de la silice (SiO2), appelée à l état pur cristal de roche; élément constitutif fréquent des roches cristallines (granites, rhyolithes, etc.), de certaines roches sédimentaires… …   Encyclopédie Universelle

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  • Quartz — ist die Grafikschicht des Apple Betriebssystems Mac OS X. Bei Quartz handelt es sich um eine Bibliothek für 2D und 3D Grafiken, die das grundlegende Darstellungsmodell für Mac OS X bildet. Aufbauend auf dem plattformübergreifenden PDF Standard… …   Deutsch Wikipedia

  • Quartz — Quartz, n. [G. quarz.] (Min.) A form of silica, or silicon dioxide ({SiO2}), occurring in hexagonal crystals, which are commonly colorless and transparent, but sometimes also yellow, brown, purple, green, and of other colors; also in… …   The Collaborative International Dictionary of English

  • quartz — [kwo:ts US kwo:rts] n [U] [Date: 1700 1800; : German; Origin: quarz] a hard mineral substance that is used in making electronic watches and clocks ▪ quartz crystals ▪ a quartz watch …   Dictionary of contemporary English

  • Quartz — der; es, e <aus engl. quartz> engl. Schreibung von dt. Quarz (z. B. zur Kennzeichnung von quarzgesteuerten Uhren) …   Das große Fremdwörterbuch

  • quartz — (n.) 1756, from Ger. Quarz rock crystal, from M.H.G. twarc, probably from a W.Slavic source (Cf. Czech tvrdy, Polish twardy quartz ), from O.C.S. tvrudu hard …   Etymology dictionary

  • quartz — [kwôrts] n. [Ger quarz < ?] any of various crystallized forms of silica that are transparent, translucent, or colored, used in many ways, esp. as a gem or in making glass, lenses, or quartz crystals: see MOHS SCALE quartzose [kwôrts′ōs΄] adj …   English World dictionary

  • quartz — [ kwɔrts ] noun uncount a hard shiny stone often used inside electronic equipment and watches …   Usage of the words and phrases in modern English

  • quartz — ► NOUN ▪ a hard mineral consisting of silica, typically occurring as colourless or white hexagonal prisms. ORIGIN German Quarz, from Polish dialect kwardy, corresponding to Czech tvrdý hard …   English terms dictionary

  • quartz|it|ic — «kwawrt SIHT ihk», adjective. of the nature of or consisting of quartzite …   Useful english dictionary


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