Chalcopyrite, Copper iron sulphide,
Formula CuFeS₂

Crystal system: Tetragonal.
Hardness: 3.5 to 4
Density: 4.2 gms/cm³
Colour: Brassy
Streak: Greenish-black

Chalcopyrite is the most important copper ore and the most abundant copper mineral. Copper is an economically important metal; used in alloys, in electrical cabling for its excellent conductivity, and for copper piping.

The specimen shown comes from the East Pool Mine, Redruth, Cornwall.