mineral

Limonite (Iron Ore)

FeO(OH)·nH2O

Hardness: 4-5.5 (Mohs scale); Color: Yellow-brown to black; Luster: Dull, earthy to submetallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Yellow-brown to black
Luster: Dull, earthy to submetallic

Identified July 20, 2026More mineral →

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Physical properties

Hardness: 4-5.5 (Mohs scale); Color: Yellow-brown to black; Luster: Dull, earthy to submetallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7-4.3

Formation & geological history

Formed by the oxidation of iron-rich mineral deposits (like pyrite/magnetite) or through the precipitation in swampy environments (bog iron). Common in weathering zones of ore bodies.

Uses & applications

Historically used as a major source of iron ore; currently used as a pigment in paints (yellow ochre) and for mineral specimens.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals. It was once the primary source of iron for ancient civilizations and is the source of the yellow color in most desert sands.

Field identification & locations

Identified by its signature yellow-brown streak, earthy habit, and association with other oxidized iron minerals. Common in sedimentary layers and weathered gossans.