sedimentary

Weathered iron-rich rock or concretion

Likely limonite/goethite-bearing concretion; exact identification requires testing

AI-generated identification · may be incorrect

Brown-yellow, earthy to dull luster, rounded and heavily weathered surface with dark iron-oxide streaking; hardness roughly 4–5.5 Mohs, opaque, with no obvious cleavage or crystal faces.

Identified August 14, 2026More sedimentary →

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Physical properties

Brown-yellow, earthy to dull luster, rounded and heavily weathered surface with dark iron-oxide streaking; hardness roughly 4–5.5 Mohs, opaque, with no obvious cleavage or crystal faces.

Formation & geological history

Probably formed by groundwater cementing sediment with hydrated iron oxides, or by weathering of an iron-bearing host rock. Such concretions commonly form in sedimentary deposits during the Quaternary or older geological periods.

Uses & applications

Primarily a field or teaching specimen; iron-rich material can be an ore, but this small rounded piece has little industrial value and is not gem-quality.

Geological facts

Limonite is a variable mixture of hydrated iron oxides rather than a single true mineral; yellow-brown coloration typically reflects goethite and related oxides.

Field identification & locations

Common in soils, stream gravels, weathered rock, and sedimentary formations worldwide. A rusty streak, relatively high density, and possible attraction to a strong magnet help distinguish it from ordinary brown stones; a scratch test and streak test are useful.