Pyrite

Physical Properties

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

Formation & Geological History

Formed in igneous, metamorphic, and sedimentary rocks. It common creates in hydrothermal veins through sulfur-rich fluids, as a magmatic segregation, or as an authigenic mineral in sedimentary environments where oxygen is limited.

Uses & Applications

Historically a source of sulfur for sulfuric acid production; used today as a minor ore of iron, in jewelry (often called 'marcasite'), and widely collected by hobbyists for its aesthetic crystal formations.

Geological Facts

Commonly known as 'Fool's Gold' because its color and shimmer often deceived prospectors. Unlike gold, pyrite is brittle and leaves a greenish-black streak, whereas gold is malleable and leaves a yellow streak.

Field Identification & Locations

Identify by its cubic crystals, metallic brassy luster, and hardness (it can scratch glass). Found globally, with notable deposits in Spain, Italy, Peru, and the USA. Collectors look for sharp, well-defined cubic faces and tarnish-free surfaces.

Identified on: 4/19/2026

Mode: Standard