Migmatite's a rock at the frontier between igneous and metamorphic rocks. They can also be known as diatexite. Migmatites form under extreme temperature conditions during prograde metamorphism, where partial melting occurs in pre-existing rocks. Migmatites aren't crystallized from a totally molten material, and aren't generally the result of solid-state reactions. Migmatites are composed of a leucosome, new material crystallized from incipient melting, and a mesosome, old material that resisted… (More on Migmatite)