Pyrite (Fool's Gold)

Physical Properties

Hardness: 6-6.5 on Mohs scale; Color: Pale brass-yellow; 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 via hydrothermal veins, contact metamorphism, or as a primary/secondary mineral in sedimentary sequences. It occurs in environments with low oxygen and high sulfur contents.

Uses & Applications

Historically used as a source of sulfur and sulfuric acid. Today, it is popular in jewelry (as marcasite), used in lithium batteries, and widely collected as a decorative mineral specimen.

Geological Facts

Known as 'Fool's Gold' because it was often mistaken for real gold by prospectors. Unlike gold, which is soft and leaves a yellow streak, pyrite is brittle and leaves a greenish-black streak. It can actually create sparks when struck against steel.

Field Identification & Locations

Identify by its brittle nature and brassy metallic luster. Common in mining districts worldwide, such as Rio Tinto (Spain) and various locations in Peru and the USA. Useful for distinguishing from gold via streak test or hardness test.

Identified on: 4/23/2026

Mode: Standard