sedimentary

Rounded ironstone concretion

Iron-rich sedimentary concretion, commonly composed of goethite and/or hematite cementing sand or clay

AI-generated identification · may be incorrect

Smooth, rounded, ochre-brown surface with scattered dark spots; likely opaque and earthy to dull-lustrous. Hardness and crystal structure cannot be determined from the image; iron oxides range roughly 5–6.5 Mohs.

Identified September 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as iron minerals cemented sediment around a nucleus during diagenesis. Concretions occur in sedimentary rocks of many ages; the specimen’s age and exact composition are not identifiable visually.

Uses & applications

Mostly collected as a natural curiosity or used decoratively; iron-rich material can be an iron ore where concentrated, but this specimen’s grade is unknown.

Geological facts

Concretions often develop rounded shapes as minerals precipitate outward through surrounding sediment, sometimes preserving fossils or internal bands.

Field identification & locations

Look for a dense, earthy brown-to-rust exterior and, if broken, a contrasting interior or concentric layers; a streak test and density check can help distinguish ironstone. Iron-rich concretions are widespread in sedimentary terrains worldwide.