Bornite is a copper iron sulfide often mistaken for another copper iron sulfide chalcopyrite. These two copper iron sulfides have different formulas and form in different crystal systems. Bornite is the original peacock copper ore. But acid washed chalcopyrite is often called peacock copper ore. Bornite is usually massive. So crystals like these are rare. This crystal comes from the Milpillas Mine Cuitaca, Mun. De Santa Cruz Sonora, Mexico.