mineral

Limonite

Limonite (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 4.0-5.5; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal Structure: Amorphous (often pseudomorphous); Specific Gravity: 2.7-4.3

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

Identified June 23, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal Structure: Amorphous (often pseudomorphous); Specific Gravity: 2.7-4.3

Formation & geological history

Formed usually by the oxidation and hydration of iron-rich sulfide minerals through weathering; found in secondary enrichment zones of ore deposits.

Uses & applications

Historically used as an iron ore; currently used as a pigment (brown ochre) in paints and coatings; also a source of iron for primitive iron extraction.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals, primarily goethite. It was the source of yellow and brown pigments in prehistoric cave paintings.

Field identification & locations

Identify by its characteristic yellowish-brown streak and dull appearance. It is commonly found in gossans (iron caps) over sulfide deposits and in bog iron environments.