It has a brassy to golden yellow colour and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black. On exposure to air, chalcopyrite oxidises to a variety of oxides, hydroxides and sulfate
Chalcopyrite is rarely found in association with native copper and is often confused with pyrite, although the latter has a cubic and not a tetragonal crystal system. Further, chalcopyrite is often massive, rarely crystalline, and less brittle. Chalcopyrite is also a darker yellow in color, with a greenish tinge and diagnostic greasy luster.
Due to its color and high copper content, chalcopyrite has often been referred to as "yellow copper".
Natural chalcopyrite has no solid solution series with any other sulfide minerals. There is limited substitution of Zn with Cu despite chalcopyrite having the same crystal structure as sphalerite.