mineral

Limonite (Iron Ore)

Limonite (Hydrated iron oxide - FeO(OH)·nH2O)

Hardness: 4-5.5; Color: Yellowish-brown to brownish-orange; Luster: Dull or earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3.

Hardness: 4-5
Color: Yellowish-brown to brownish-orange
Luster: Dull or earthy

Identified April 12, 2026More mineral →

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Physical properties

Hardness: 4-5.5; Color: Yellowish-brown to brownish-orange; Luster: Dull or earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3.

Formation & geological history

Formed as a secondary mineral through the weathering of iron-rich ores or as a precipitate in bogs, lakes, and marine environments. Can occur in any geological age where oxidation occurs.

Uses & applications

Historically used as a major source of iron ore; currently used as an earthy pigment (yellow ochre) in paints, dyes, and cosmetics.

Geological facts

Limonite is not a true mineral but a mineraloid composed of a mixture of hydrated iron oxides. It was once the primary source of iron for indigenous cultures and early industrial 'bog iron' smelting.

Field identification & locations

Identify by its characteristic yellowish-brown streak, lack of magnetism, and earthy texture. Commonly found in gossans (weathered tops of ore veins) and as coatings on other rocks.

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