sedimentary

Iron-rich concretion or weathered ironstone

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

AI-generated identification · may be incorrect

Brown to rusty orange, earthy to dull metallic luster, irregular massive texture, and no visible crystal faces; hardness typically 4–5.5 Mohs, with moderate-to-high density and possible yellow-brown streak.

Identified August 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed by oxidation and cementation of iron-bearing sediments or minerals near Earth’s surface; such concretions commonly formed during weathering from the Cenozoic to recent geologic ages.

Uses & applications

Used historically as iron ore and yellow-brown pigment, but this specimen is mainly suitable for collecting or educational display.

Geological facts

The rusty coloration results from iron oxidation, similar to the process that creates rust on steel; limonite is a mixture rather than a single precisely defined mineral.

Field identification & locations

Identify it by its heavy feel, earthy rusty coating, brown-yellow streak, and attraction to a strong magnet if magnetite or goethite is present. Common in weathered soils, sedimentary layers, and iron-rich gravels worldwide.