||This article needs additional citations for verification.
(November 2009)| Most pegmatites are composed of quartz,
feldspar and mica; in essence a granite. Rarer intermediate
composition and mafic pegmatites 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 pegmatites, with crystals usually over 5 cm in size.
Individual crystals over 10 metres across have been found, and
the world's largest crystal was found within a pegmatite.
Similarly, crystal texture and form within pegmatitic rock may
be taken to extreme size and perfection. Feldspar within a
pegmatite may display exaggerated and perfect twinning,
exsolution lamellae, and when affected by hydrous
crystallization, macroscale graphic texture is known, with
feldspar and quartz intergrown. Perthite feldspar within a
pegmatite often shows gigantic perthitic texture visible to the
naked eye. Ge