mineral

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

Hardness: 6-6.5 (Mohs); Color: Pale brass-yellow to golden yellow; Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: Poor/Indistinct; Specific Gravity: 4.9-5.2

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

Identified March 18, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs); Color: Pale brass-yellow to golden yellow; Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: Poor/Indistinct; Specific Gravity: 4.9-5.2

Formation & geological history

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, and in sedimentary environments (shales/coal beds) via oxygen-depleted biological activity.

Uses & applications

Used primarily as a source of sulfur and in the production of sulfuric acid for industry. Historically used in wheel-lock guns and today popular in jewelry (often sold as 'marcasite') and for mineral collection.

Geological facts

Despite the name 'Fool's Gold,' pyrite sometimes contains trace amounts of actual gold. It can produce sparks when struck against steel, which made it vital for early firearms development.

Field identification & locations

Identify in the field by its brittle nature (it crushes to black powder, unlike gold which is malleable) and its greenish-black streak when rubbed on unglazed porcelain. Commonly found globally, with notable deposits in Spain, Italy, and the USA.