megacryst

Updated About encyclopedia.com content Print Article Share Article
views updated

megacryst Applied to the texture of any igneous or metamorphic rock which contains large, usually euhedral crystals set in a finer-grained groundmass. The term has no genetic connotation, unlike ‘phenocryst’ which implies crystallization from a magma, and ‘porphyroblast’ which implies solid-state recrystallization during metamorphism.