sedimentary

Iron-rich concretion or weathered ironstone

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

AI-generated identification · may be incorrect

Brown to rusty yellow-brown, earthy to dull/submetallic luster, granular and strongly weathered; typically Mohs 4–5.5, with no obvious cleavage and variable density. The surface appears oxidized and may contain quartz, clay, or other sedimentary matrix.

Identified August 15, 2026More sedimentary →

Explore Iron-rich concretion or weathered ironstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Likely formed by groundwater oxidation and cementation of iron-bearing sediment, producing a concretion or ironstone nodule; exact age cannot be determined from the photograph. Such material commonly develops in soils, sedimentary basins, and weathering zones.

Uses & applications

Used historically as an iron ore and natural pigment; attractive pieces are collected, but this specimen is generally unsuitable for jewelry or construction unless part of an aggregate or decorative-stone collection.

Geological facts

Limonite is a field term for mixtures of hydrated iron oxides rather than one distinct mineral. A yellow-brown streak, earthy texture, and reddish-brown weathering are characteristic.

Field identification & locations

Check for a yellow, ochre, or brown streak on unglazed porcelain, high specific gravity, and attraction to a strong magnet if magnetite is present; avoid destructive tests on valuable specimens. Common in iron-rich soils and sedimentary regions worldwide.