pegmatite

n. crystalline granite

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.Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite". Rarer "intermediate" and "mafic" pegmatite containing amphibole, Ca-plagioclase feldspar, pyroxene and other minerals are known, found in recrystallised zones and apophyses associated with large layered intrusions.Crystal size is the most striking feature of pegmatite, with crystals usually over 50mm in size. However, individual crystals over 10 meters across have been found, and the world's largest crystal was found within a pegmatite.
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Noun
1. a form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements
(hypernym) igneous rock
(substance-meronym) samarskite

n. pegmatite, crystalline granite

n. (Geology) pegmatite, crystalline granite