How to identify pyrite

The four-property portrait

Pyrite is generous with evidence. Its crystals are geometry lessons — cubes, octahedra and the twelve-faced pyritohedron, frequently with fine parallel striations ruled across the faces — and no natural gold ever shows those forms. Its brass-yellow surface grays noticeably in shade. A knife point cannot scratch it at Mohs 6 to 6.5, though it can shatter it, because pyrite is hard and brittle at once. And on unglazed tile it draws a greenish-black line, the single check that ends every gold conversation; the method behind that line lives on the streak test page.

Massive pyrite — no crystal faces, just brassy metallic lumps or flecks in rock — leans harder on the last three properties, and on company: it grows in quartz veins, black shale, and coal country, often alongside the very minerals it gets mistaken for.

The brass family, split by the right tool

Each row falls to a different tool, which is the point of the table: the knife separates chalcopyrite, shelf-life separates marcasite — the same iron sulfide in a less stable arrangement, notorious for decaying to gray crumbs and sulfur smell in collections — and the streak plate is really only needed for the gold question. That question has its own full page: how to identify gold in rocks runs the shade, dent and streak sequence from the prospecting side.

Where pyrite turns up, and what it is worth

Pyrite is among the most widespread sulfides on Earth: quartz veins, slates and schists, black shales where it grows sharp little cubes, coal seams, and fossil beds — ammonites and shells replaced by pyrite are collectible in their own right. The concretions in Ohio’s black shales split to brassy cores regularly, per Ohio rock identification, and every gold district carries it, which is how it earned the nickname that follows it everywhere.

Its value is a specimen story, not a metal one. Sharp Spanish cubes, radial pyrite suns from Illinois coal country and bright undamaged clusters all sell steadily; crushed massive pyrite is worth effectively nothing, and a yellow metallic find that might be the other thing belongs in the elimination sequence of how to identify valuable rocks before anyone gets excited. One care note earns its place here: marcasite-rich and fine-grained pyrite specimens can sour with humidity — white crust, sulfur smell — so display pieces live best dry.