Chalcopyrite on Dolomite- Sweetwater Mine, Reynolds County, Missouri. 6cm tall Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical formula CuFeS2. A major ore of copper, common in sulfide veins and disseminated in igneous rocks. Chalcopyrite oxidises to a variety of oxides, hydroxides and sulfates. Weathering may lead to the formation of malachite, azurite, brochantite, langite and numerous other secondary copper minerals.