Pyrite in Matrix (Fool's Gold)

Physical Properties

Hardness: 6-6.5 Mohs; Color: Pale brass-yellow to golden; Luster: Metallic; Crystal Structure: Isometric (often cubic or pyritohedral); Cleavage: Indistinct; Specific Gravity: 4.8-5.0

Formation & Geological History

Formed in igneous, metamorphic, and sedimentary environments through hydrothermal activity or authigenic precipitation in oxygen-poor sediments.

Uses & Applications

Historical source of sulfur and sulfuric acid; today used in jewelry (as 'marcasite'), mineral collecting, and as a component in lithium batteries.

Geological Facts

Known as 'Fool's Gold' because its color and weight are deceptive to novice prospectors. It can emit sparks when struck against steel, a property that led to its use in wheel-lock firearms.

Field Identification & Locations

Identify by its brittle nature (gold is malleable), brassy color, and greenish-black streak when rubbed on unglazed porcelain. Commonly found in quartz veins or sedimentary shales worldwide.

Identified on: 5/9/2026

Mode: Standard