mineral

Pyrite (Fool's Gold)

Iron Sulfide (FeS2)

Hardness: 6-6.5 (Mohs scale), Color: Brass-yellow, Luster: Metallic, Crystal Structure: Isometric/Cubic, Cleavage: Indistinct, Specific Gravity: 4.9-5.2

Hardness: 6-6

Identified April 10, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs scale), Color: Brass-yellow, Luster: Metallic, Crystal Structure: Isometric/Cubic, Cleavage: Indistinct, Specific Gravity: 4.9-5.2

Formation & geological history

Formed in hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks such as shale and coal. It forms across various geological ages.

Uses & applications

Source of sulfur and sulfuric acid in industry; used in some jewelry (often sold as 'marcasite'); used as a grounding stone by collectors; historically used to start fires (flint and steel).

Geological facts

Its name comes from the Greek word 'pyr' meaning fire, because it emits sparks when struck by steel. It is often mistaken for gold, leading to its nickname 'Fool's Gold'.

Field identification & locations

Identify by its brittle nature (unlike malleable gold), greenish-black streak when rubbed on a strike plate, and cubic crystal habits. Found globally, prominent in Peru, Spain, and the USA.