sedimentary

Ironstone concretion

Iron-oxide-rich sedimentary concretion, likely dominated by goethite and/or hematite

AI-generated identification · may be incorrect

Small, rough, ochre-brown specimen with an earthy to dull luster; hardness and composition cannot be determined reliably from the image. Ironstone concretions vary in mineral content and have no single crystal structure.

Identified October 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when iron minerals cement sediment into a compact nodule, often during diagenesis. Its age and exact formation environment cannot be determined from appearance alone.

Uses & applications

Commonly collected as a geological specimen; iron-rich rocks have also been used as iron ore where deposits are sufficiently concentrated.

Geological facts

Brown and yellow coloration commonly results from oxidized iron minerals such as goethite and hematite.

Field identification & locations

Look for a dense, rusty-colored nodule with an irregular surface; a streak test and close inspection can help distinguish ironstone from other rocks. Ironstone occurs in sedimentary deposits worldwide.