mineral

Limonite (Gossan)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Hardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3

Hardness: 4-5
Color: Yellowish-brown to dark brown
Luster: Dull, earthy

Identified June 17, 2026More mineral →

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Physical properties

Hardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3

Formation & geological history

Formed as a secondary mineral through the oxidation and weathering of primary iron-bearing sulfide minerals like pyrite or chalcopyrite in the upper portions of ore deposits (Gossans).

Uses & applications

Used historically as a source of iron ore and as a pigment (yellow ochre) for paints and dyes. Primarily a geological indicator for deeper metal deposits.

Geological facts

Limonite is not a true mineral species but a mixture of hydrated iron oxide minerals, mostly goethite. It has been used as a pigment for over 30,000 years, found in Neolithic cave paintings.

Field identification & locations

Identify by its characteristic yellowish-brown streak or 'rusty' appearance. Common in weathered outcrops of mining districts. Collectors look for botryoidal (grape-like) or iridescent surfaces.

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