mineral

Limonite (Iron Stone/Gossen)

Limonite (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3.

Hardness: 4
Color: Yellowish-brown to dark brown
Luster: Dull or earthy

Identified March 30, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3.

Formation & geological history

Formed by the oxidation and hydration of iron-rich mineral deposits (like pyrite or magnetite) in weathering zones near the surface. Can be found in Bog iron deposits or as a 'gossan' cap over ore bodies.

Uses & applications

Historically used as a low-grade iron ore and as a pigment for ochre. Today, it is primarily of interest to geologists and collectors as an indicator of underlying metal deposits.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals, mostly goethite. It was one of the earliest pigments used by humans for cave paintings and pottery.

Field identification & locations

Identify by its characteristic yellowish-brown streak (when rubbed on unglazed porcelain) and its 'rusty' appearance. Commonly found in sedimentary environments or as a weathering crust. Collectors look for 'pseudomorphs' where limonite has replaced the shape of other crystals.