CoachA migmatite is a composite silicate rock, heterogeneous at the outcrop scale, made of darker parts with the look of a metamorphic rock and lighter parts of plutonic look. Its leucosome is its light, quartz- and feldspar-rich part; its melanosome its dark part, rich in dark minerals, complementary to the leucosome; its mesosome the part of intermediate colour, a more or less modified relict of the parent rock (the paleosome). The leucosome and the melanosome together form the neosome, the newly formed part. A metatexite is a migmatite with discrete, well-defined leucosomes, mesosomes and melanosomes; a diatexite is one in which light and dark parts merge in streaks (schlieren) and ghost-like (nebulitic) structures.
