mineral

Limonite (Iron Ore)

Limonite (FeO(OH)·nH2O)

Hardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (lacks definite crystal shape); Cleavage: None; Specific Gravity: 2.7 to 4.3.

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

Identified March 20, 2026More mineral →

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Physical properties

Formation & geological history

Formed by the oxidation and hydration of iron-rich mineral deposits (like pyrite or magnetite) in sedentary or metamorphic environments. Can form at any geological age where iron minerals are exposed to weathering.

Uses & applications

Historically used as a lower-grade iron ore; used as a natural pigment (ochre) for paints and dyes; currently mostly used for architectural pigments and cement production.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxides. It was a primary source of iron for ancient civilizations and is the main component of 'yellow ochre' used in prehistoric cave paintings.

Field identification & locations

Identify in the field by its distinct mustard-yellow to brown streak (scraped against porcelain) and earthy texture. Commonly found in gossans (weathered tops of ore veins) and bog iron deposits worldwide.