mineral

Pyrite

Iron Sulfide (FeS2)

Hardness: 6-6.5 (Mohs); Color: Brass-yellow; Luster: Metallic; Crystal system: Isometric/Cubic; Cleavage: Poor/Indistinct; Specific Gravity: 4.9-5.2.

Hardness: 6-6
Color: Brass-yellow
Luster: Metallic

Identified June 30, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs); Color: Brass-yellow; Luster: Metallic; Crystal system: Isometric/Cubic; Cleavage: Poor/Indistinct; Specific Gravity: 4.9-5.2.

Formation & geological history

Formed in igneous, metamorphic, and sedimentary environments. Often found in hydrothermal veins, as an accessory mineral in igneous rocks, or as replacement nodules in sedimentary beds like shale.

Uses & applications

Historically used as a source of sulfur and sulfuric acid. Today, it is used in the production of lithium batteries, as a gemstone (sold as 'marcasite'), and is a popular collector's mineral.

Geological facts

Commonly known as 'Fool's gold' because its color resembles gold, though it is much harder and more brittle. It can produce sparks when struck against steel, which made it useful for early firearms like the wheel-lock.

Field identification & locations

Identify by its brassy color, cubic crystal habit, and blackish-green streak on a porcelain plate. The location near Minnesota (45.1°N, 93.8°W) makes this likely a specimen from glacial drift or found in local shale deposits.