mineral

Limonite (vibrant yellowish-brown iron oxide)

Limonite (FeO(OH)·nH2O)

Hardness: 4.0-5.5; Color: Yellowish-brown to ochre; Luster: Dull to earthy; Crystal structure: Amorphous (often pseudomorphic after pyrite); Specific Gravity: 2.7-4.3

Hardness: 4
Color: Yellowish-brown to ochre
Luster: Dull to earthy

Identified April 7, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5; Color: Yellowish-brown to ochre; Luster: Dull to earthy; Crystal structure: Amorphous (often pseudomorphic after pyrite); 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, magnetite, and siderite. Often found in gossipans (iron hats) above ore deposits.

Uses & applications

Historically used as a major source of iron ore; currently used as a natural pigment (yellow ochre) in paints, dyes, and cosmetics.

Geological facts

Limonite is not a true mineral in the strict sense but a mixture of hydrated iron oxide minerals, predominantly goethite. It was the source of some of the earliest pigments used in prehistoric cave paintings.

Field identification & locations

Identify in the field by its distinct yellow-brown streak, earthy habit, and association with weathered iron deposits. Found worldwide in oxidized zones of ore veins and as bog iron.

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