Dark-coloured, rounded areas, up to 2 mm in diameter and sometimes larger, found on the surface of slaty cleavage in low- to medium-grade contact metamorphic rocks (see contact metamorphism) of pelitic composition. Many spots are graphite-rich, having formed by metamorphic aggregation from organic material originally disseminated through the starting sedimentary shale. Rocks may also have a spotty appearance when andalusite is beginning to appear in contact-metamorphosed pelites.