The Chalcopyrite reference article from the English Wikipedia on 24-Jul-2004
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Chalcopyrite

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Chalcopyrite is a sulfide mineral that crystallises in the tetragonal system. It has chemical composition CuFeS2, a golden yellow colour and hardness 3,5 to 4 on the Mohs scale.

Chalcopyrite is one of the most important copper ores. Due to its colour it is often confused with Pyrite though this mineral has a cubic and not a tetragonal crystal system. Chalcopyrite is also somewhat more yellowish in colour.