mineral

Limonite

Limonite (Hydrous iron oxides, FeO(OH)·nH2O)

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (lacks internal structure); Streak: Yellowish-brown; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Yellowish-brown to dark brown
Luster: Dull, earthy

Identified April 6, 2026More mineral →

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Physical properties

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (lacks internal structure); Streak: Yellowish-brown; Specific Gravity: 2.7-4.3

Formation & geological history

Formed as a secondary mineral through the weathering and oxidation of other iron-bearing minerals like pyrite, magnetite, and hematite in oxidation zones. It often forms through bog-iron deposits in marshy environments.

Uses & applications

Major historical ore of iron; used as a pigment (yellow ochre) in paints and dyes; currently used as a minor iron ore and for specimen collecting.

Geological facts

Limonite is not a true mineral species but a mixture of hydrous iron oxides (mostly goethite). It was one of the first pigments used by early humans in cave paintings.

Field identification & locations

Identify in the field by its distinctive yellowish-brown streak on a porcelain plate and its earthy, dull appearance. It is found globally in gossans, bog deposits, and weathered ore outcrops.

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