mineral

Weathered Pyrite Nodule

Iron Sulfide (FeS2) undergoing oxidation to limonite/goethite

AI-generated identification · may be incorrect

Hardness of 6-6.5 for unweathered pyrite, but surface weathering creates a softer outer layer (1-5.5). Color is brassy yellow internally, weathering to rusty brown, orange, and reddish-brown. Luster is metallic to earthy. Crystal habit is cubic, pyritohedral, or massive.

Identified August 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed in sedimentary, igneous, and metamorphic environments through hydrothermal precipitation or low-temperature sedimentary processes involving sulfur and iron. Subject to surface weathering (oxidation) when exposed to air and moisture, turning the iron sulfide into iron oxides/hydroxides.

Uses & applications

Mostly collected by amateur rockhounds and mineral enthusiasts; historically used to strike fire and as a source of sulfur and sulfuric acid.

Geological facts

Commonly known as 'fool's gold' due to its superficial resemblance to gold, pyrite often weathers into rusty nodules that beginners frequently mistake for gold nuggets.

Field identification & locations

Found worldwide in sedimentary shales, coal beds, and hydrothermal veins. Identify by its characteristic rusty orange surface coating, brownish streak, and heavy weight relative to its size.