chalcopyrite

Chalcopyrite is a copper–iron sulfide mineral (CuFeS₂) and the single most abundant copper ore on Earth. It’s brassy yellow, metallic, and often confused with pyrite or even gold — but its properties make it easy to identify.

What Chalcopyrite Is
Chemical formula: CuFeS₂

Mineral class: Sulfide

Crystal system: Tetragonal

Color: Brass‑yellow, sometimes with purple/blue iridescent tarnish

Luster: Metallic

Streak: Greenish‑black (a key diagnostic)

Hardness: 3.5–4 (softer than pyrite)

Density: 4.1–4.3 g/cm³

Tenacity: Brittle

How to Tell It Apart
Chalcopyrite is often mistaken for pyrite or gold, but:

It is softer than pyrite (can be scratched with a knife).

It is harder and brittle, unlike gold which is soft and malleable.

Its streak is green‑black, not black (pyrite) or yellow (gold).

Where It Forms
Chalcopyrite appears in many copper‑bearing environments, especially:

Porphyry copper deposits (the world’s main copper source)

Hydrothermal veins

Massive sulfide deposits

It is commonly associated with bornite, chalcocite, covellite, malachite, azurite, and occasionally cuprite.

Why It Matters
According to the U.S. Geological Survey, chalcopyrite is the world’s most abundant copper source, essential for electrical wiring, electronics, and renewable‑energy technologies.

It weathers easily at the surface, contributing to acid rock drainage when exposed in mine waste — an important environmental consideration.

Name & History
The name comes from Greek:

chalkos = copper

pyrites = “striking fire”