mineral

Pyrite (Fool's Gold)

Iron Disulfide (FeS2)

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

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

Identified March 22, 2026More mineral →

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Physical properties

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

Formation & geological history

Forms in a wide variety of geological settings including hydrothermal veins, sedimentary rocks (shale, limestone, coal), and metamorphic rocks. It forms across various geological ages through the reaction of sulfur and iron in reducing environments.

Uses & applications

Used in the production of sulfuric acid and sulfur dioxide. While sometimes used in costume jewelry (often sold as 'marcasite'), it is primarily a collector's specimen and is occasionally used in paper manufacturing and as a semiconductor material.

Geological facts

Famous for its nickname 'Fool's Gold' because it misled prospectors during the gold rush; unlike gold, pyrite is brittle and leaves a greenish-black streak. It can also produce sparks when struck against steel, leading to its name derived from the Greek word 'pyr' meaning fire.

Field identification & locations

Identify in the field by its distinct brassy luster, cubic crystal habit, and high hardness (it cannot be scratched by a copper penny or a fingernail). Found globally, with notable deposits in Spain, Italy, Peru, and the USA. Collectors look for well-defined cubic or dodecahedral faces.