Pegmatite meaning

pĕgmə-tīt
A coarse-grained granite, sometimes rich in rare elements such as uranium, tungsten, and tantalum.
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Any of various coarse-grained igneous rocks that often occur as wide veins cutting across other types of rock. Pegmatites form from water-rich magmas or lavas that cool slowly, allowing the crystals to grow to large sizes. Although pegmatites can be compositionally similar to a number of rocks, they most often have the composition of granite.
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A coarsely crystalline igneous or plutonic rock composed primarily of feldspar and quartz, normally with muscovite and/or biotite mica. Often contains other minerals, which may be of economic importance. Pegmatite is chemically identical to granite, but has a much coarser crystal structure. Common colors are gray, white, and pink. Pegmatite is quarried for decorative stone and as a source of beryllium, columbium and tantalum when these are present. Gemstones of the quartz/silicate family may also be found in pegmatites.
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A light-colored, coarsegrained, intrusive igneous rock, usually granitic, containing large crystals of quartz, feldspar, and mica, and sometimes rare minerals: typically found in fissures of other igneous rocks.
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Origin of pegmatite

  • Greek pēgma pēgmat- something fastened together (from pēgnunai to fasten pag- in Indo-European roots) –ite

    From American Heritage Dictionary of the English Language, 5th Edition