mineral

Limonite (Ochreous)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Color: Brown to yellowish-brown; Hardness: 4 to 5.5 on Mohs scale; Luster: Dull or earthy; Crystal Structure: Amorphous or cryptocrystalline; Cleavage: None; Specific Gravity: 2.7 to 4.3.

Hardness: 4 to 5
Color: Brown to yellowish-brown
Luster: Dull or earthy

Identified May 7, 2026More mineral →

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Physical properties

Color: Brown to yellowish-brown; Hardness: 4 to 5.5 on Mohs scale; Luster: Dull or earthy; Crystal Structure: Amorphous or cryptocrystalline; Cleavage: None; Specific Gravity: 2.7 to 4.3.

Formation & geological history

Formed primarily by the chemical weathering of iron-rich minerals such as pyrite, magnetite, and siderite in oxidation zones of ore deposits or within sedimentary beds.

Uses & applications

Used historically and currently as a pigment (brown ochre) for paints and dyes. Known as an iron ore, though less preferred than hematite due to its water content.

Geological facts

Limonite is not a singular mineral species but a complex of hydrated iron oxides. It was one of the first pigments used by early humans in cave paintings, such as those at Lascaux.

Field identification & locations

Identified in the field by its distinct yellow-brown streak, earthy appearance, and lack of magnetism compared to other iron minerals. Commonly found in boggy environments or as gossans atop metal veins.

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