sedimentary

Limonite/iron-oxide concretion

Hydrated iron oxides, commonly goethite (FeO(OH)) with variable limonite mixture

AI-generated identification · may be incorrect

Brown to ochre, earthy-to-submetallic luster, irregular porous texture; hardness roughly 4–5.5 Mohs, variable composition and no consistent crystal form. The image suggests a rusty, iron-rich mass, but fine details are unclear.

Identified October 10, 2026More sedimentary →

Explore Limonite/iron-oxide concretion 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

Forms as iron minerals weather and oxidize near Earth’s surface, often accumulating in soil, sediment, or cavities; commonly geologically recent to ancient depending on host deposits.

Uses & applications

Iron ores are used for iron and steel production; attractive forms are collected, while ordinary specimens have little commercial value.

Geological facts

“Limonite” is a field term for mixtures of hydrated iron oxides rather than a single mineral species.

Field identification & locations

Look for ochre-brown color, earthy texture, and a rusty streak; it commonly occurs in weathered iron-rich rocks and soils. Similar-looking rocks require a streak or composition test for confident identification.