Mineral · Chalcopyrite group
Chalcopyrite
CuFeS2
Chalcopyrite is the brassy copper iron sulfide, the world's principal copper ore, found as sphenoidal crystals with pyrite and sphalerite in the Tri-State, Peru, Mexico and Cornwall. It is softer and more yellow than pyrite and tarnishes to iridescent blues and purples. Most 'peacock ore' sold is acid-tarnished chalcopyrite rather than bornite.
| Formula | CuFeS2 |
|---|---|
| IMA status | grandfathered |
| Crystal system | Tetragonal |
| Mohs hardness | 3.5–4 |
| Group | Chalcopyrite group |
| Type locality | None |
| Streak | Greenish black |
| Specific gravity | 4.2 |
| Reference list | IMA List of Minerals (RRUFF) — verify formula and status against the current list |
Fakes and treatments
'Peacock ore' is usually chalcopyrite treated with acid to force an iridescent tarnish; it is a treatment, not a natural bornite specimen.
Elsewhere
Cite this article
Stratum Study. "Chalcopyrite" (Mineral). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/minerals/chalcopyrite. Accessed 2026-09-20.
@misc{stratum-chalcopyrite,
title = {Chalcopyrite},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/minerals/chalcopyrite}},
year = {2026},
note = {Mineral article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, wikidata, commons. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.