An extremely coarse-grained ( 2 cm) igneous rock, usually silicic.

Course-grained igneous rock, usually granite that is characterized by large well-formed crystals and often contains rare elements.

vein of extremely coarse grained granite, often containing economic amounts of rare elements.

A coarse-grained igneous rock containing crystals of up to tens of centimeters across and occurring in dike-shaped intrusions.

(peg'-ma-tite) A typically coarse-grained igneous rock formed through the crystallization of the very-last stages of magma typically granitic in composition that is enriched in water and other volatile elements (F, Cl) and, in some cases, highly incompatible elements (lithium, beryllium, boron, fluorine, niobium, tantalum, uranium, and the rare earth elements) that do not fit into the structures of minerals crystallized at higher temperatures and pressures. Although most pegmatites are composed of the common minerals feldspar, quartz, muscovite, and biotite, pegmatites rich in incompatible elements may also contain rare minerals. These incompatible elements make up a tiny fraction of the original magma, but because they are concentrated in the water-rich residual melt, they can occur in large enough quantities to produce large, well-formed crystals of beryl, chrysoberyl and euclase (beryllium), tourmaline (boron), topaz (fluorine), apatite (chlorine and fluorine), spodumene and lepidolite or lithium-rich pyroxene and mica, monazite (rare earth elements), tantalite (tantalum), and columbite (niobium).

Natural igneous rock formation consisting of a variety of granite usually characterized by coarse texture caused by crystallization from an exceptionally fluid magma rich in mineralizers containing rare elements

A very coarse grained igneous rock, normally of granitic composition. Typically forms during the final states of magma chamber crystallization when the high water content solutions allow rapid crystal growth.

Light-colored, very coarse-grained intrusive igneous rock, composed of feldspar, quartz, and micas; frequently can be seen in highway roadcuts as light-colored parallel and cross cutting veins and lenses in the metamorphic rock of the uplands; occasionally is a host for gem minerals. Pegmatite is a common and economically important rock type in Connecticut. It occurs in bodies too small to show on a state-scale geologic map. The Branchville area of western Connecticut and the Middletown area of eastern Connecticut have pegmatites of particular significance.

Very coarse grained rocks of granitic composition containing large mineral crystals.

A coarse-grained igneous rock with exceptionally large crystals, formed from a magma that contains a high proportion of water.

a form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements

a body of plutonic rock which contains unusually large crystals

an extremely slow-cooling igneous rock in which very large crystals can form

an igneous body with an extremely coarse grain size

an igneous rock distinguished by its abnormally large crystals

a small body of igneous rock that is formed from the crystallization of molten rock

a very coarse-grained rock, similar to granite in composition

a very coarse grained rock that formed from the last part of a magma chamber below the earth's surface

An exceptionally coarse-grained igneous rock, with interlocking crystals, usually found as irregular dikes, lenses, or veins, esp. at the margins of batholiths.

A very coarse-grained igneous rock, usually occurring in irregular dikes, lenses, or veins. Can be simple or complex. Pegmatite dikes are very important to the collector, as pockets filled with crystals are often present.

It is a very coarse-grained igneous rock which is characterized by crystals of more than 3 cm in length.

an igneous rock that is very coarse grained in texture, and granitic in composition containing the minerals quartz and alkali feldspar. Most pegmatites form as veins or lens-shaped bodies.

A very coarse-grained igneous rock, commonly with a granitic composition. Usually forms from molten rock rich in water or other volatiles that facilitate the growth of large crystals. Forms sills and dikes.

very coarse-grained igneous rock, with most grains interlocking and greater than one centimeter in diameter. The composition usually is granitic. Peg-matites represent the last and most water-rich portion of a magma to crystallize and hence contain high concentrations of minerals present only in trace amounts in typical granites. Often these minerals are rich in such elements as lithium, boron, fluorine, niobium, tantalum, uranium, and rare-earth elements like cerium.

A light coloured igneous rock containing large crystals of the minerals mica, quartz and feldspar.

a very coarse-grained igneous rock occurring in sills and dikes, and usually containing crystals of the common minerals found in granite, but sometimes containing rare minerals rich in such elements as lithium, uranium, and tantalum. [AHDOS

Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.