Rock and Mineral Identification Reference

How to Identify Pyrite (Fool's Gold): Hardness, Streak, Luster and Tests

Quick answer

Pyrite (Fool's Gold) (mineral): 6 identifying properties, 1 home test, and how to tell it from Gold, quoted from geology department and survey sources.

Updated 2026-09-10 · Sources: University of Minnesota Common Minerals

Scratch, streak and acid tests mark the specimen, and some produce sharp fragments or dust. Wear eye protection, work in a ventilated space, keep acid off skin, and never taste a mineral you have not already identified.

How to Identify Pyrite (Fool's Gold): Hardness, Streak, Luster and Tests — Photo: Didier Descouens · CC BY-SA 4.0 · source

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What are the key facts?

Type: Mineral
Mohs hardness: 6–6.5
Streak: Greenish black or brownish black.
Luster: Metallic luster, opaque; faint striations may be visible on crystal or cleavage faces.
Color: Pale brassy yellow; darkens and may develop iridescence upon oxidation/tarnishing.
Cleavage or fracture: No cleavage; conchoidal fracture.
Specific gravity: 5 or higher

What Pyrite (Fool's Gold) looks like

The properties that identify Pyrite (Fool's Gold) — mohs hardness: 6–6.5; streak: Greenish black or brownish black; luster: Metallic luster, opaque; faint striations may be visible on crystal or cleavage faces; color: Pale brassy yellow; darkens and may develop iridescence upon oxidation/tarnishing; cleavage or fracture: No cleavage; conchoidal fracture; specific gravity: 5 or higher. Hardness, streak and cleavage are the reliable ones; color alone rarely settles it.

Tests you can do at home

Crystal-form test: pyrite commonly forms cubes or octahedrons, with faint striations on crystal or cleavage faces.

Often confused with

Gold: Gold is soft and malleable with a golden-yellow streak and no crystal faces; pyrite is hard and brittle, commonly forming cubic or octahedral crystals.

Where it is found in North America

The Upper Mississippi River Valley lead-zinc mining district, and massive sulfide deposits in northern Minnesota/Wisconsin.

How to photograph it for identification

Photograph a fresh, unweathered surface in daylight, then a second shot of any crystal faces or broken edge. Include a coin for scale. If you did a streak test, photograph the streak next to the specimen. The app suggests the likely mineral or rock; confirm with hardness and the tests above before you label it.

FAQ

How hard is Pyrite (Fool's Gold) on the Mohs scale?

6–6.5. A fingernail is about 2.5, a copper coin about 3, a steel knife 5.5 and glass about 5.5, so test against those.

What color streak does Pyrite (Fool's Gold) leave?

Greenish black or brownish black. Rub the specimen on an unglazed porcelain tile; the powder color is the streak, and it is more consistent than the specimen color.

How do I tell Pyrite (Fool's Gold) from Gold?

Gold is soft and malleable with a golden-yellow streak and no crystal faces; pyrite is hard and brittle, commonly forming cubic or octahedral crystals.

What is the simplest test for Pyrite (Fool's Gold)?

Crystal-form test: pyrite commonly forms cubes or octahedrons, with faint striations on crystal or cleavage faces.

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Sources

University of Minnesota Common Mineralscommonminerals.esci.umn.edu/minerals-o-s/pyrite

Compiled by the RockLens editorial team

Every fact on this page is taken from the sources listed above; numbers and prices are copied from the source, and prices name the guide or auction and its date. Research and drafting were assisted by AI, and each claim was then checked against the cited sources. Checked 2026-09-10. We do not buy, sell or grade items; the app identifies what you photograph and points you to these references.