Pyrite

Physical Properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal Structure: Isometric (cubic, octahedral, pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8-5.02

Formation & Geological History

Formed in high and low-temperature hydrothermal veins, as an accessory mineral in igneous rocks, and by magmatic segregation. It also forms in sedimentary rocks via bacterial reduction of sulfates in oxygen-poor environments. It can be found in rocks of all geological ages.

Uses & Applications

Historical source of sulfur for sulfuric acid. Used today in fossil fuel refining, as an electrode material in lithium batteries, and as a popular specimen for collectors and jewelry (often called 'marcasite' in the trade).

Geological Facts

Commonly known as 'Fool's Gold' because its color and high specific gravity can deceive novice prospectors. Unlike gold, pyrite is brittle and creates a greenish-black streak when rubbed against a touchstone, whereas gold is malleable and leaves a yellow streak.

Field Identification & Locations

Identify in the field by its brassy color, cubic crystal habits, and the 'sulfur' smell released when struck. Commonly found in association with quartz, coal, and metallic ores. Found globally in locations like Spain, Peru, Italy, and the USA.

Identified on: 5/9/2026

Mode: Standard