sedimentary

Iron-rich concretion or weathered ironstone

Limonite/goethite-rich ironstone; commonly hydrated iron oxides (FeO(OH)·nH₂O)

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to dull luster, irregular botryoidal or porous surface; typically Mohs 4–5.5, with no visible cleavage and a brown-yellow streak. The image alone cannot confirm mineral identity.

Identified August 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms through oxidation and concentration of iron-bearing minerals in soils, sediments, and weathered rock; commonly associated with laterite, bog iron, and sedimentary iron deposits. Formation may range from recent weathering to ancient sedimentary environments.

Uses & applications

Used historically as an iron ore and natural pigment; attractive pieces may be collected, but this small specimen has little commercial value.

Geological facts

Limonite is a field term for hydrated iron oxides rather than a single precisely defined mineral. Goethite and hematite commonly occur together, producing rusty red-brown coloration.

Field identification & locations

Look for a yellow-brown to reddish streak, earthy texture, high apparent density, and attraction to a strong magnet if magnetite is present. Common in weathered soils, stream gravels, and iron-rich sedimentary formations worldwide.