Pegmatite Wikipedia
A pegmatite is an igneous rock, formed underground, with interlocking crystals usually larger than cm in size (1 in).Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called word pegmatite derives from Homeric Greek, πήγνυμι (pegnymi), which means "to bind together", in reference to the intertwined crystals of quartz ...