mineral

Limonite (Yellow Ochre)

Hydrated iron(III) oxide-hydroxides (FeO(OH)·nH2O)

Hardness: 4.0-5.5; Color: Yellowish-brown to brownish-black; Luster: Dull or earthy; Crystal Structure: Amorphous (lacks internal structure); Streak: Yellow-brown; Specific Gravity: 2.7-4.3.

Hardness: 4
Color: Yellowish-brown to brownish-black
Luster: Dull or earthy

Identified May 4, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5; Color: Yellowish-brown to brownish-black; Luster: Dull or earthy; Crystal Structure: Amorphous (lacks internal structure); Streak: Yellow-brown; Specific Gravity: 2.7-4.3.

Formation & geological history

Formed as a secondary mineral through the chemical weathering of iron-rich minerals such as pyrite, magnetite, and hematite in oxidising environments.

Uses & applications

Historically used as a pigment (Yellow Ochre) for paint and cave art. In some regions, it is used as a low-grade iron ore.

Geological facts

Limonite was one of the first pigments used by early humans; it has been found in cave paintings dating back thousands of years. It often forms a 'gossan' or 'iron hat' over mineral deposits.

Field identification & locations

Identify in the field by its distinct yellow-brown earthy appearance and yellow streak when rubbed on a porcelain plate. Common in bog deposits and weathered soil zones.

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