sedimentary

Limonite Concretion

Hydrated Iron(III) Oxide-Hydroxide (FeO(OH)wnH2O)

AI-generated identification · may be incorrect

Hardness: 4-5.5 (Mohs scale), Color: Yellowish-brown to dark brown, Luster: Dull or earthy, Crystal Structure: Amorphous or nanocrystalline, Cleavage: None, Specific Gravity: 2.7-4.3

Hardness: 4-5

Identified July 14, 2026More sedimentary →

Explore Limonite Concretion in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 4-5.5 (Mohs scale), Color: Yellowish-brown to dark brown, Luster: Dull or earthy, Crystal Structure: Amorphous or nanocrystalline, Cleavage: None, Specific Gravity: 2.7-4.3

Formation & geological history

Formed by the oxidation of iron-bearing minerals or by precipitation from iron-rich groundwater in sedimentary environments. Common in swampy areas or bog-iron deposits.

Uses & applications

Historically used as a low-grade iron ore and as a pigment for ochre paints. Today, primarily collected by hobbyists or used in educational displays.

Geological facts

Limonite is not a true mineral but a mixture of similar hydrated iron oxide minerals, mainly goethite. It has been used as a pigment (Yellow Ochre) since prehistoric times for cave paintings.

Field identification & locations

Identify by its brownish-yellow streak on ceramic surfaces and its lack of magnetism compared to magnetite. Found in sedimentary basins, marshes, and weathered ore outcrops worldwide.