Chalcopyrite. Chalcopyrite, copper iron sulfide (CuFeS2}, is one of the most widespread and important ores of copper. It occurs both as disseminated grains in a host rock, and also in vein-type deposits along with pyrite, galena, sphalerite and other sulfide minerals. Chalcopyrite has a golden yellow colour, but the surface tarnishes rapidly upon exposure to air leaving a characteristic brightly colored iridescent film.