mineral

Limonite

Limonite (FeOO·nH2O)

Hardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown, Luster: Dull or earthy, Crystal Structure: Amorphous/microcrystalline, Cleavage: None, Specific Gravity: 2.7-4.3

Hardness: 4

Identified April 6, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown, Luster: Dull or earthy, Crystal Structure: Amorphous/microcrystalline, Cleavage: None, Specific Gravity: 2.7-4.3

Formation & geological history

Formed as a secondary material through the oxidation or chemical weathering of iron-rich minerals such as pyrite, magnetite, or siderite. Common in sedimentary deposits and hydrothermal veins.

Uses & applications

Historically used as an iron ore. Primarily used today as a pigment (ochre) for paints and dyes. Historically used by ancient civilizations as body paint.

Geological facts

Limonite is not a true mineral in the strict sense, but a mixture of hydrated iron oxide minerals, mostly Goethite. It is the substance that gives many soils their yellow or brown color.

Field identification & locations

Identify in the field by its distinctive yellowish-brown streak (using a streak plate), its earthy appearance, and lack of magnetism compared to other iron ores like magnetite. Found globally in iron hats or 'gossans' above ore deposits.