Pegmatite's a very coarse-grained igneous rock that's a grain size of 10 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's the most striking feature of pegmatite, with crystals usual… (More on Pegmatite)