chalcopyrite vs. pyrite

a very common mineral, copper iron sulfide, CuFeS 2 , occurring in brass-yellow crystals or masses: the most important ore of copper; copper pyrites.

a very common brass-yellow mineral, iron disulfide, FeS 2 , with a metallic luster, burned to sulfur dioxide in the manufacture of sulfuric acid: chemically similar to marcasite, but crystallizing in the isometric system.