Pyrite

Physical Properties

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

Formation & Geological History

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, in contact metamorphic rocks, and in sedimentary rocks such as shale and coal. It forms through the reaction of iron and sulfur in oxygen-poor environments.

Uses & Applications

Major source of sulfur for sulfuric acid production; used in the jewelry industry (marketed as 'marcasite'); historically used in firearms (wheel-locks) to create sparks; collected as a popular display mineral.

Geological Facts

Commonly known as 'Fool's Gold' due to its resemblance to precious metal. Unlike gold, pyrite is brittle and leaves a dark streak. Famous deposits are found in Rio Tinto (Spain) and Huanzala (Peru).

Field Identification & Locations

Identify in the field by its distinct metallic brassy color, hardness (it can scratch glass, while gold cannot), and its greenish-black streak. It is often found associated with quartz veins and other sulfides. Common worldwide.

Identified on: 4/13/2026

Mode: Standard