mineral

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Hardness: 4.0-5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3

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

Identified June 20, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5; 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 weathering and oxidation of iron-bearing minerals like pyrite, magnetite, and hematite in sedimentary environments.

Uses & applications

Historically used as an iron ore and as a pigment for ochre paint. Occasionally used in industrial purification processes.

Geological facts

Limonite is not a single mineral but a mixture of hydrated iron oxide minerals. It was the primary source of 'yellow ochre' used in prehistoric cave paintings.

Field identification & locations

Identified by its distinctive yellowish-brown streak on a porcelain plate and lack of magnetism compared to magnetite. Found in wetlands as 'bog iron'.