Pyrite

Physical Properties

Hardness: 6-6.5 on Mohs scale. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Isometric (often forms cubes, pyritohedrons, or octahedrons). Cleavage: Poor/indistinct. Specific gravity: 4.95-5.10.

Formation & Geological History

Forms in a wide variety of geological environments: as a primary mineral in igneous rocks, as a contact metamorphic mineral, and in sedimentary rocks (often replacing organic material or forming nodules). Can be of any geological age.

Uses & Applications

Historically used for producing sulfur dioxide for the paper industry and sulfuric acid. Sometimes used in jewelry (often marketed as 'marcasite'). Popular among mineral collectors.

Geological Facts

Commonly known as 'Fool's Gold' because its brassy color and metallic luster led inexperienced prospectors to mistake it for real gold. Unlike gold, pyrite is brittle and leaves a greenish-black streak.

Field Identification & Locations

Identify in the field by its brass-yellow color, metallic luster, cubic or pyritohedral crystal habit, and greenish-black streak on a streak plate. It is much harder than gold (which has a hardness of 2.5-3). Found worldwide, with notable deposits in Spain, Peru, Italy, and the USA.

Identified on: 4/15/2026

Mode: Advanced