mineral

Pyrite

Iron Sulfide (FeS2)

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

Hardness: 6-6
Color: Pale brass-yellow with occasional rainbow tarnish
Luster: Metallic

Identified June 21, 2026More mineral →

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Physical properties

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

Formation & geological history

Forms in diverse geological environments including hydrothermal veins, sedimentary rocks under reducing conditions, and contact metamorphic deposits. It exists in rocks of almost every geological age.

Uses & applications

Primarily used as a source of sulfur and in the production of sulfuric acid. Historically used in jewelry (marcasite jewelry) and as a spark-inducer for early firearms. Today, widely popular as a decorative specimen for collectors.

Geological facts

Likely the most famous mineral error in history, its resemblance to gold led to the name Fool's Gold. It can produce sparks when struck against steel. Some specimens form perfectly geometric cubes naturally.

Field identification & locations

Identify by its hardness (destroys a steel knife whereas gold is soft) and greenish-black streak. Common in mining districts worldwide, such as Peru, Spain, and North America. Collectors should ensure specimens are kept away from high humidity to prevent decomposition.