Chalcopyrite, Copper iron pyrite, formula CuFeS₂

Crystal system: Tetragonal.
Hardness: 3.5 to 4
Density: 4.2
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 as well as electrical cabling for its excellent conductivity and copper piping.

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