Pegmatite

Peg″ma‐tite (?), n. [From Gr. πη̑γμα something fastened together, in allusion to the quartz and feldspar in graphic granite: cf. F. pegmatite. See Pegm.] (Min.) (a) Graphic granite. See under Granite. (b) More generally, a coarse granite occurring as vein material in other rocks.