mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Hardness: 6-6.5 Mohs. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric. Cleavage: Indistinct. Specific gravity: Approx 5.0.

Hardness: 6-6
Color: Pale brass-yellow
Luster: Metallic

Identified April 10, 2026More mineral →

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Physical properties

Hardness: 6-6.5 Mohs. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric. Cleavage: Indistinct. Specific gravity: Approx 5.0.

Formation & geological history

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, and in sedimentary rocks like shale and coal through chemical precipitation in oxygen-poor environments.

Uses & applications

Major source of sulfur used to produce sulfuric acid; historically used as a spark ignition source in firearms; used in cheap costume jewelry (often sold as 'marcasite'); important indicator mineral for gold prospecting.

Geological facts

Famous for the 'Fool's Gold' nickname because its color misled many novice prospectors. Pyrite is actually heavier than most common yellow rocks but much lighter and harder than real gold, which is soft enough to be scratched by a knife.

Field identification & locations

Identify by its brittle nature (gold is malleable) and its green-black streak when rubbed on a porcelain plate. Common in mining districts worldwide, especially in the Rio Tinto region of Spain and across the United States.