granite
granite. (Image by David.Monniaux, GFDL)

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Granite

Granite

Granite, which makes up 7080% of Earth's crust , is an igneous rock formed of interlocking crystals of quartz , feldspar , mica, and other minerals in lesser quantities. Large masses of granite are a major ingredient of mountain ranges. Granite is a plutonic rock, meaning that it forms deep underground. Slow cooling gives atoms time to migrate to the surfaces of growing crystals, resulting in a coarse or mottled crystalline structure easily visible to the naked eye.

Geologists have debated rival theories of granite's origin for over 150 years. The two theories most favored today are the magmatic theory and the hypermetamorphic theory. Supporters of the magmatic theory observe that granite is strongly associated with mountain ranges, which in turn tend to follow continental edges where one plate is being subducted (wedged under another). Tens of kilometers beneath the continental edge, the pressure and friction caused by subduction are sufficient to melt large amounts of rock. This melted rock or magma ascends toward the surface as large globules or plutons, each containing many cubic kilometers of magma. Apluton does not emerge suddenly onto the surface but remains trapped underground, where it cools slowly and may be repeatedly injected from beneath with pulses of fresh magma. To become surface rock, a solidified pluton must finally be uplifted to the surface and stripped bare by erosion .

The ultrametamorphic theory, in contrast, argues that granite is not formed from raw magma but consists of sedimentary rock thoroughly melted and re-crystallized. Most geologists now argue that granites can be formed by magmatism, ultrametamorphosis, or a combination of both.

Until recently, geologists thought that plutons of granitic magma would require millions of years to ascend to the surface. However, laboratory experiments with melted rock has shown that granitic magma is thin and runny enough (i.e., of low viscosity) to squirt rapidly upward to the surface through small cracks in the crust. Granite plutons may thus be created in 1,000100,000 years, rather than in the millions of years previously thought. The precise origin and process of granite formation continues to be a subject of active research.

See also Bowen's reaction series; Convergent plate boundary; Plate tectonics

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granite

granite, coarse-grained igneous rock of even texture and light color, composed chiefly of quartz and feldspars. It usually contains small quantities of mica or hornblende, and minor accessory minerals may be present. Depending on the feldspar present, granite may be pink, dark gray, or light gray. It is commonly believed to have solidified from molten rock (called magma) under pressure. However, some granites show no contacts with surrounding wall rock, but instead gradually grade into metamorphic rock. Others show relic features found in sediments. This evidence suggests that some granites are not igneous in origin, but metamorphic. Some granites are the oldest known rocks on earth; others were formed during younger geologic periods. Crystallized at depth, granite masses are exposed at the earth's surface by crustal movement or by the erosion of overlying rocks. Very coarse-grained granite, called pegmatite, may contain minerals and gemstones of economic value. Such pegmatites are found in the Black Hills of South Dakota. Granite has been used since ancient times as a building material.

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"granite." The Columbia Encyclopedia, 6th ed.. 2016. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

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granite

granite A light-coloured, coarse-grained, igneous rock, consisting of essential quartz (at least 20%), alkali feldspar, mica (biotite and/or muscovite), with or more commonly without amphibole, and accessory apatite, magnetite, and sphene. Hypersolvus granites are characterized by one type of alkali feldspar, usually microperthite, whereas subsolvus granites are characterized by two types of alkali feldspar: microperthite and albite. Granite can be formed by partial melting of old continental crust, on a local scale by in situ replacement of continental crust (granitization), by fractional crystallization of basalt magma, or by a combination of these processes.

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AILSA ALLABY and MICHAEL ALLABY. "granite." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "granite." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O13-granite.html

AILSA ALLABY and MICHAEL ALLABY. "granite." A Dictionary of Earth Sciences. 1999. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-granite.html

granite

gran·ite / ˈgranit/ • n. a very hard, granular, crystalline, igneous rock consisting mainly of quartz, mica, and feldspar and often used as a building stone. ∎  used in similes and metaphors to refer to something very hard and impenetrable: [as adj.] a man with granite determination. DERIVATIVES: gra·nit·ic / grəˈnitik/ adj. gran·it·oid / ˈgraniˌtoid/ adj. & n. ORIGIN: mid 17th cent.: from Italian granito, literally ‘grained,’ from grano ‘grain,’ from Latin granum.

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"granite." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

"granite." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O999-granite.html

"granite." The Oxford Pocket Dictionary of Current English. 2009. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-granite.html

granite

granite. Coarse-grained hard igneous crystalline rock composed of feldspar, mica, and quartz, usually grey or dark red, and capable of taking a high polish. Used by the Ancient Egyptians (e.g. for obelisks), it was also employed by the Romans for, e.g. the shafts of columns. As industrialized methods of cutting stone developed in C19, the material was frequently used for ashlar work, and especially for funerary monuments in the new cemeteries.

Bibliography

N. Davey (1961);
W. McKay (1957);
W. Papworth (1852)

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JAMES STEVENS CURL. "granite." A Dictionary of Architecture and Landscape Architecture. 2000. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

JAMES STEVENS CURL. "granite." A Dictionary of Architecture and Landscape Architecture. 2000. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O1-granite.html

JAMES STEVENS CURL. "granite." A Dictionary of Architecture and Landscape Architecture. 2000. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O1-granite.html

granite

granite Coarse-grained, light-grey, durable igneous rock, composed chiefly of feldspar and quartz, with some mica or hornblende. It is thought to have solidified from magma (molten rock). It is a valuable construction material.

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"granite." World Encyclopedia. 2005. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

"granite." World Encyclopedia. 2005. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O142-granite.html

"granite." World Encyclopedia. 2005. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-granite.html

granite

granite XVII. — It. granito lit. grained, granular, pp. formation on grano grain.
Hence granitic XVIII.

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T. F. HOAD. "granite." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

T. F. HOAD. "granite." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O27-granite.html

T. F. HOAD. "granite." The Concise Oxford Dictionary of English Etymology. 1996. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O27-granite.html

granite

granite Granite City informal name for Aberdeen.
Granite State informal name for New Hampshire.

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ELIZABETH KNOWLES. "granite." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

ELIZABETH KNOWLES. "granite." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. (August 28, 2016). http://www.encyclopedia.com/doc/1O214-granite.html

ELIZABETH KNOWLES. "granite." The Oxford Dictionary of Phrase and Fable. 2006. Retrieved August 28, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O214-granite.html

granite

granitedammit, Hammett, Mamet •emmet, semmit •helmet, pelmet •remit • limit • kismet • climate •comet, grommet, vomit •Goldschmidt •plummet, summit •Hindemith •hermit, Kermit, permit •gannet, granite, Janet, planet •magnet • Hamnett • pomegranate •Barnet, garnet •Bennett, genet, jennet, rennet, senate, sennet, sennit, tenet •innit, linnet, minute, sinnet •cygnet, signet •cabinet • definite • Plantagenetbonnet, sonnet •cornet, hornet •unit •punnet, whodunnit (US whodunit) •bayonet • dragonet • falconet •baronet • coronet •alternate, burnet •sandpit • carpet • armpit • decrepit •cesspit • bear pit • fleapit •pipit, sippet, skippet, snippet, tippet, Tippett, whippet •limpet • incipit • limepit •moppet, poppet •cockpit • cuckoo-spit • pulpit • puppet •crumpet, strumpet, trumpet •parapet • turnspit

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"granite." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 28 Aug. 2016 <http://www.encyclopedia.com>.

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