ˈpegməˌtīt noun
( -s )
Etymology: French, from Greek pēgmat-, pēgma something fastened together, framework + French -ite
1. : graphic granite
2.
a. : a natural igneous rock formation consisting of a variety of granite that occurs in dikes or veins and is usually characterized by extremely coarse texture caused by crystallization from an exceptionally fluid magma rich in mineralizers containing rare elements that frequently form unusual minerals (as tourmaline spodumene, beryl)
b. : a similar formation in a rock other than granite
syenite pegmatite
diorite pegmatite