sedimentary

Ironstone concretion (likely hematite-rich)

Iron-oxide-cemented sediment, chiefly hematite (Fe₂O₃) and/or goethite (FeO(OH))

AI-generated identification · may be incorrect

Reddish-brown, earthy to dull luster, with a rough iron-rich rind and harder gray-brown interior; hardness and density vary with composition. The photo does not reveal diagnostic crystal structure or cleavage.

Identified October 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when iron oxides cement sediment or precipitate around a nucleus, often during groundwater movement and weathering. Its age and exact formation environment cannot be determined from the image alone.

Uses & applications

Ironstone is used as iron ore where iron content is sufficient; attractive pieces may be kept as geological specimens, but this example does not appear gem-grade.

Geological facts

Iron oxides produce the characteristic rusty red-brown colors and can coat or cement other minerals.

Field identification & locations

Look for high density, rusty streak or coatings, and iron-rich cement; hematite gives a reddish-brown streak, while goethite commonly gives yellow-brown. Ironstone occurs widely in sedimentary terrains worldwide.