granite

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granite,

coarse-grained igneous rockrock,
aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
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 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.

granite

An igneous rock having crystals or grains of visible size; consists mainly of quartz and mica or other colored minerals.
See also: Stone

Granite

 

a magmatic rock rich in silica.

One of the most common rocks of the earth’s crust, granite is composed of potash feldspar (orthoclase, microcline), acid plagioclase (albite, oligoclase), quartz, mica (biotite or muscovite), amphibole, and, more rarely, pyroxene. The structure of granite is usually holocrystalline and frequently por-phyraceous and gneissoid-banded. It is predominant among intrusive rocks and occupies an essential place in the geologic structure of the Urals, the Caucasus, the Ukraine, Karelia, the Kola Peninsula, Middle Asia, and Siberia. Granitic intrusions date from the Archean and Cenozoic eras. Granite usually occurs in rocks in the form of batholiths, laccoliths, bosses, and veins. During the formation and cooling of the granitic bodies a regular system of joints arises; the jointing is. as a result, characteristically parallelepipedal, columnar, or sheetlike in natural exposures. The rounding of corners through weathering forms hammock jointing. The weathering of granite takes the form of disintegration or kaolinization. Deeper changes in the granite can be produced by pneumatolytic processes, resulting in the formation of greisen with lithia mica or tourmaline.

The origin of granite, in addition to its scientific interest, has great practical importance, since certain granitic bodies are associated with deposits of various valuable metals, such as tin, wolfram, molybdenum, lead, and zinc. Pegmatitic veins, which in certain cases are sources of rare-metal mineralization and high quality raw materials for ceramics (for example, feldspar, mica, and muscovite), are associated genetically with granite.

Because of its physical and mechanical properties, granite is an excellent building material. Its massiveness. density, and wide textural potentials (the ability to take on a mirrorlike polish, on which light brings out the play of colors of the ingrained mica, or the sculptural expressiveness of the unpolished rough stone, which absorbs light) make granite one of the basic materials for monumental sculpture. Granite is also used in obelisks, columns, and as a facing for many buildings. Most of the granite used in the USSR comes from quarries in the Ukraine, the Urals, and Karelia.

REFERENCES

Levinson-Lessing, F. Iu. Izbrannye trudy, vol. 4: Petrografiia. 1955.
Menert, K. Novoe o probleme granitov. Moscow, 1963. Petrov, V. P. “Sovremennoe sostoianie predstavlenii o magme i problema granita.” Izv. AN SSSR: Ser. geol., 1964. no. 3.

granite

[′gran·ət]
(petrology)
A visibly crystalline plutonic rock with granular texture; composed of quartz and alkali feldspar with subordinate plagioclase and biotite and hornblende.

granite

1. An igneous rock having crystals or grains of visible size; consists mainly of quartz, feldspar, and mica or other colored minerals.
2. In the building stone industry, a crystalline silicate rock having visible grains; this includes gneiss and igneous rocks that are not granite in the strict sense.

granite

1. a light-coloured coarse-grained acid plutonic igneous rock consisting of quartz, feldspars, and such ferromagnesian minerals as biotite or hornblende: widely used for building
2. another name for a stone
References in periodicals archive ?
In fact, some minor granitoid intrusions and cross-cutting granite veins resembling the Riga rocks have previously been distinguished also in the charnockitoid wall rocks to the south of the batholith (Bogatikov & Birkis 1973).
Petrogenetic interpretation of granitoid rock series using muticationic parameters.
Therefore, as a part of the composition were held equivalent replacement granitoid screenings on basalt in the range of 2.
Granitoid cobbles were explosively transported to surface in pebble dykes (diatremes) at this time and may have breached the developing orebodies, causing further brecciation (Stewart 1987).
Neodymium and strontium isotopic constraints on the origin of the peraluminous granitoids of the South Mountain Batholith, Nova Scotia, Canada.
The gamma-ray spectrometry data were particularly useful for distinguishing various granitoid plutons and internal zoning within them, whereas the magnetic data permitted differentiation of the plutons from gneissic basement and enclaves of supracrustal rocks within the gneissic basement.
833 Ga, thus being similar to Backaby granitoids of southern Sweden aged 1.
Preliminary investigation of major and trace element abundances of 20 granitoid rocks from 16 different plutons in eastern Maine supports growing evidence that granitoid magmatism associated with terrane accretion during the Silurian to Devonian in this region involved reworking of the continental crust in a variety of tectonic settings.
Hard granitoid rocks occur in the Pyrenees, but had they been exploited to any significant extent we would expect to find granitic material on sites such as Ampurias, which is not the case.
All drill holes intersected significant thicknesses of alteration and mineralization hosted in foliated granitoid and mafic volcanic rocks.
Lithogeochemistry, petrology, and the acid-generating potential of the Goldenville and Halifax groups and associated granitoid rocks in the metropolitan Halifax Regional Municipality, Nova Scotia, Canada.
This accretion has been recognized in Colombia by the presence of Jurassic (Ibague [T3J-Pi]; Mocoa, Algeciras batholiths) and Cretaceous (Antioquia batholith) granitoid rocks that intrude the Cajamarca Complex east of the Central Cordillera.