Pyrite (Iron Pyrite)

Physical Properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal Structure: Isometric (often cubic, pyritohedral, or octahedral); Cleavage: Indistinct; Specific Gravity: 4.9-5.2.

Formation & Geological History

Formed in diverse geological environments including hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks like shale and coal. It can form at various geological ages from the Precambrian to the present.

Uses & Applications

Historically a source of sulfur and sulfuric acid; today it is used in jewelry (often sold as 'marcasite'), as a collector specimen, and occasionally in the production of lithium-ion batteries and solar panels.

Geological Facts

Commonly known as 'Fool's Gold' due to its metallic luster and brassy hue which often confuses beginner prospectors. Unlike gold, it is brittle and will leave a greenish-black streak when rubbed on a porcelain plate.

Field Identification & Locations

Identify in the field by its brassy color, high hardness (it can scratch glass), and cubic crystal habits. It is found globally, with famous deposits in Spain, Italy, and the USA. Collectors look for sharp, mirror-like crystal faces.

Identified on: 4/25/2026

Mode: Standard