Botryoidal Pyrite

Physical Properties

Hardness: 6-6.5 (Mohs scale), Color: Brass-yellow with metallic luster, Crystal Structure: Isometric/Cubic (arranged in rounded botryoidal clusters), Cleavage: Indistinct, Specific Gravity: 4.8-5.0

Formation & Geological History

Formed in hydrothermal veins, sedimentary rocks, or metamorphic deposits. This specific 'botryoidal' or bubbly form often precipitates rapidly from iron-rich fluids in low-temperature environments or within voids in sedimentary host rocks.

Uses & Applications

Primary source of sulfur and iron in industrial history; today mainly a collector's specimen, used in lapidary work/jewelry (often called marcasite in jewelry), and used for making sulfuric acid.

Geological Facts

Also known as 'Fool's Gold' due to its resemblance to precious metals. Botryoidal (grape-like) growth habit is much rarer for pyrite than the traditional cubic crystal form. It can sometimes undergo 'pyrite disease' where humidity causes it to crumble over time into white powder.

Field Identification & Locations

Identify by its 'grape-cluster' shape, heavy metallic weight, and brassy color. Streak test will yield a greenish-black powder, unlike gold's yellow streak. Found globally, with notable deposits in Spain, Peru, and the USA.

Identified on: 4/19/2026

Mode: Standard