Chalcopyrite

Chalcopyrite, also known as Peacock Ore, is a copper iron sulfide mineral. It's natural color is a yellow-gold. It produces an oxidized layer that creates its beautiful peacock rainbow color when acid washed.

 

Chalcopyrite was named in 1725 by Johann Friedrich Henckel from the Greek words chalkos (copper) and pyrites (strike fire). 

The difference between Pyrite and Chalcopyrite is their chemical composition. Pyrite is FeS2; Chalcopyrite is CuFeS2.