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, octahedral, or pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8-5.0.

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

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Forms in a wide variety of geological environments: as an accessory mineral in igneous rocks, in hydrothermal veins (precipitating from hot sulfur-rich fluids), and in sedimentary rocks where oxygen is low (anoxic conditions). It is found in rocks ranging from the Archean era to modern times.

Uses & applications

Historically used as a source of sulfur and sulfuric acid. Today, it is primarily used as a minor iron ore, in jewelry (known as 'marcasite' jewelry), as a semiconducting material in lithium batteries, and as popular specimens for mineral collectors.

Geological facts

Pyrite is often mistaken for gold because of its color; however, it is much harder than gold (gold can be scratched by a knife, pyrite cannot) and has a greenish-black streak whereas gold has a golden streak. It can create sparks when struck against steel, which is why its name comes from the Greek word 'pyr' meaning fire.

Field identification & locations

Identify in the field by its distinct cubic crystal shapes, metallic pale-yellow shine, and its brittle nature (it shatters under pressure, while gold flattens). Commonly found in the United States (Colorado, Illinois), Peru, Italy, and Spain. Collectors should look for sharp, mirror-like cubic faces.