mineral

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

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 July 14, 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 material through the oxidation and weathering of primary iron-bearing minerals (like pyrite or magnetite) in hydrothermal veins or sedimentary deposits.

Uses & applications

A major source of iron ore; historically used as a pigment (brown ochre) and currently sought for mineral specimens.

Geological facts

Limonite is not a single mineral but a mixture of hydrated iron oxide minerals, primarily goethite. It has been used as a pigment by humans since prehistoric times in cave paintings.

Field identification & locations

Identify by its characteristic yellowish-brown streak on a porcelain plate and its earthy, yellowish weathered appearance on outcrop surfaces. Common in gossans or 'iron hats' over sulfide deposits.