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 classic literature ?
Aramis, animated, active and young as at twenty, sprang towards the triple mass, and with his hands, delicate as those of a woman, raised by a miracle of strength the corner-stone of this great granite grave.
The lodge was a ruin of black granite and bared ribs of rafters, but facing it was a new building, half constructed, the first fruit of Sir Charles's South African gold.
Then, turning about the corner of a wall-like outcropping of granite, we came upon a smooth area of two or three acres before the base of the towering pile of ice and rock that had baffled us for days, and before us beheld the dark and cavernous mouth of a cave.
As soon as he was sound asleep she unfastened the cloak from his shoulders, threw it on her own, left the granite and stones, and wished herself home again.
Werper, from the concealment of a jutting, granite shoulder, watched him pass up from the shadows of the stairway and advance toward the edge of the hill which faced the rim of the valley where the Waziri awaited the signal of their master.
The aperture of the rock had been closed with stones, then this stucco had been applied, and painted to imitate granite.
In that granite book, begun by the Orient, continued by Greek and Roman antiquity, the Middle Ages wrote the last page.
Egyptian granite that has defied the storms and earthquakes of all time has nothing to fear from the tack-hammers of ignorant excursionists--highwaymen like this specimen.
My hands were resting upon a small piece of granite which formed a part of the wall, and all my weight upon it proved too much for it.
Having filled his arms with fragments of rotted granite, he clambered again into a tree, and it pleased him to see that the apes had followed his example.
It seemed to have been constructed for no especial use within itself, but formed merely the interval between two of the colossal supports of the roof of the catacombs, and was backed by one of their circumscribing walls of solid granite.
I could distinguish the arches springing capriciously from natural pillars, standing broad upon their granite base, like the heavy columns of Tuscan architecture.