sedimentary

Pyrite-bearing sedimentary concretion

Iron sulfide (pyrite, FeS₂) in a carbonate-rich concretion

AI-generated identification · may be incorrect

Brassy metallic crystals with angular faces occur in a tan, earthy, rounded matrix; pyrite is Mohs 6–6.5, cubic, and has no true cleavage. The host appears softer and carbonate-rich, but cannot be confirmed from the photo alone.

Identified October 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed as a concretion in sediment, with pyrite crystallizing in iron- and sulfur-rich conditions during or after burial; its age depends on the host formation and is not identifiable from the image.

Uses & applications

Small specimens are mainly collected or used for display; pyrite has industrial importance as a sulfur source, though it is not typically used as a gemstone.

Geological facts

Pyrite is often called fool’s gold, but its hard, brittle crystals and cubic forms distinguish it from malleable gold.

Field identification & locations

Look for brassy metallic luster and sharp, brittle crystal faces within the lighter matrix. Pyrite occurs worldwide in sedimentary rocks, veins, and hydrothermal deposits; avoid prolonged moisture, which can promote oxidation.