sedimentary

Limonite / Goethite (Ironstone)

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

AI-generated identification · may be incorrect

Hardness: 4-5.5; Color: Yellowish-brown to dark brown/black; Luster: Dull to sub-metallic; Cleavage: None; Habbitt: Massive or concretionary

Hardness: 4-5
Color: Yellowish-brown to dark brown/black
Luster: Dull to sub-metallic

Identified July 12, 2026More sedimentary →

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Physical properties

Hardness: 4-5.5; Color: Yellowish-brown to dark brown/black; Luster: Dull to sub-metallic; Cleavage: None; Habbitt: Massive or concretionary

Formation & geological history

Formed by the oxidation and hydration of iron-bearing minerals or by the precipitation from iron-rich water in bog or swamp environments (Cenozoic to Recent).

Uses & applications

Historically used as a minor iron ore and for brown/yellow mineral pigments (ochre). Primarily of interest to amateur collectors.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals. It was often called 'bog iron' when found in marshy areas and was the primary source of iron for early civilizations.

Field identification & locations

Identify by its yellowish-brown streak, heavy weight for its size, and absence of magnetism (unless it contains magnetite). Found globally in weathered zones of iron ore deposits.