
Chalcopyrite with Pyrite

Chalcopyrite is a copper-iron sulfide mineral that is the world's most abundant source of copper.
Chalcopyrite is often confused with pyrite and gold since all three of these minerals have a yellowish color and a metallic luster. Some important mineral characteristics that help distinguish these minerals are hardness and streak. Chalcopyrite is much softer than pyrite and can be scratched with a knife, whereas pyrite cannot be scratched by a knife. However, chalcopyrite is harder than gold, which, if pure, can be scratched by copper. Additionally, gold is malleable, while chalcopyrite is brittle. Chalcopyrite has a distinctive black streak with green flecks in it.
Locality
Krushev Dol Mine, Bulgaria

Streak
Greenish black
Hardness
Formula
3.5-4
CuFeS2
Habit
Predominantly the disphenoid and resembles a tetrahedron, commonly massive, and sometimes botryoidal.