Rock IdentifierPyrite: Fool's Gold vs Real Gold
Key takeaways
- Pyrite is hard and brittle; gold is soft and malleable.
- Pyrite streaks greenish-black; gold streaks golden-yellow.
- Pyrite forms sharp cubes; gold forms rounded nuggets and flakes.
Why the confusion
Pyrite (iron sulfide, FeS₂) earned the nickname 'fool's gold' because its brassy, metallic shine has fooled prospectors for centuries. But the two are easy to separate with a few tests once you know what to check — and the differences are dramatic, not subtle.
The decisive tests
Run these simple checks — any one of them usually settles it:
- Hardness: pyrite is hard (6–6.5) and scratches glass; gold is soft (2.5–3) and a copper coin marks it
- Streak: pyrite leaves a greenish-black streak; gold leaves a shiny golden streak
- Tenacity: pyrite is brittle and shatters when struck; gold is malleable and dents or flattens
- Shape: pyrite grows sharp cubes and pyritohedrons with striated faces; gold forms rounded nuggets, flakes, and wires
- Heft: gold is extraordinarily heavy (specific gravity ~19); pyrite feels far lighter
Chalcopyrite too
Another 'fool's gold' is chalcopyrite (copper iron sulfide), which is more golden-yellow and often tarnishes into a peacock-colored iridescence. Like pyrite, it's brittle and streaks dark greenish-black, so the same tests unmask it. Both are common, attractive, and cheap — worth collecting for themselves, just not for a fortune.
A safety note
Pyrite can slowly break down in humid air (pyrite decay/disease), releasing sulfuric acid that damages the specimen and nearby labels. Store it dry, and wash your hands after prolonged handling. This is care, not alarm — pyrite is a rockhound favorite for good reason.
