mineral

Limonite (Iron Ore)

Limonite (Hydrous iron(III) oxide-hydroxide mixture, FeO(OH)·nH2O)

Hardness: 4.0-5.5 (Mohs); Color: Yellow-brown, dark brown to black; Luster: Dull to earthy; Crystal Structure: Amorphous/Microcrystalline; Specific Gravity: 2.7-4.3.

Hardness: 4
Color: Yellow-brown, dark brown to black
Luster: Dull to earthy

Identified June 15, 2026More mineral →

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Physical properties

Hardness: 4.0-5.5 (Mohs); Color: Yellow-brown, dark brown to black; Luster: Dull to earthy; Crystal Structure: Amorphous/Microcrystalline; Specific Gravity: 2.7-4.3.

Formation & geological history

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

Uses & applications

Historically used as a major source of iron ore; also used as a natural earth pigment (yellow ochre) in paints, dyes, and cosmetics. Today, it is primarily a geological specimen or minor industrial material.

Geological facts

Limonite is not a true mineral species but an amorphous mixture of several iron-bearing minerals like goethite. It has been used as a pigment for cave paintings dating back thousands of years.

Field identification & locations

Identify by its brownish-yellow streak, lack of magnetism (usually), and earthy habit. The coordinates (Somaliland/Ethiopia region) are consistent with the presence of weathered sedimentary layers and iron-rich Precambrian formations where limonite nodules are common.

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