mineral

Pyrite

Iron Sulfide (FeS2)

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

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

Identified March 27, 2026More mineral →

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Physical properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal Structure: Isometric/Cubic; Cleavage: 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 by sedimentary precipitation in the absence of oxygen. It can be found in rocks from all geological eras.

Uses & applications

Major source of sulfur for sulfuric acid production; historically used as a source of ignition (fire-striking); used in jewelry as 'marcasite'; occasionally mined for auriferous (gold-bearing) content.

Geological facts

Commonly known as 'Fool's Gold' because its color and weight can trick beginner prospectors. Unlike real gold, it is brittle and will shatter if struck, and it leaves a greenish-black streak when rubbed on ceramic.

Field identification & locations

Identify in the field by its brassy color, cubic crystal habits, and its hardness (it can scratch glass, whereas gold cannot). Common locations include Spain (Rio Tinto), Italy, and various mines across the USA and Peru.