Pyrite

Physical Properties

Hardness: 6-6.5 on the Mohs scale. Color: Pale brass-yellow. Luster: Metallic. Crystal structure: Cubic (isometric). Cleavage: Indistinct. Specific gravity: 4.9-5.2.

Formation & Geological History

Forms in a wide range of geological environments, including igneous (magmatic segregation), sedimentary (reducing conditions in marine sediments), and metamorphic deposits. It is often found in hydrothermal veins and associated with coal beds.

Uses & Applications

Primarily used for the production of sulfur dioxide and sulfuric acid. It also has historical use in the ignition of firearms (wheel-locks) and is currently popular as a decorative specimen and in costume jewelry (often called 'marcasite').

Geological Facts

Commonly known as 'Fool's Gold' because its color resembles real gold. However, pyrite is much harder than gold and brittle, meaning it will shatter rather than flatten when struck. It can create sparks when struck against steel.

Field Identification & Locations

Identify in the field by its brassy color, cubic crystal habits, and high density. Unlike gold, pyrite has a greenish-black streak when rubbed on a porcelain plate. It is found worldwide, notably in Spain, Italy, and the USA.

Identified on: 5/11/2026

Mode: Standard