mineral

Limonite

FeO(OH)·nH2O

Hardness: 4.0 - 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous or cryptocrystalline; Cleavage: None; Specific Gravity: 2.7 - 4.3

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

Identified July 14, 2026More mineral →

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Physical properties

Hardness: 4.0 - 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous or cryptocrystalline; Cleavage: None; Specific Gravity: 2.7 - 4.3

Formation & geological history

Secondary mineral formed from the weathering/oxidation of iron-rich minerals such as pyrite, magnetite, and hematite in oxidised zones of ore deposits.

Uses & applications

A major ore of iron since prehistoric times; also used as a yellow-brown pigment in paints (yellow ochre) and ceramics.

Geological facts

Limonite is not a true mineral species but a field term for unidentified hydroxides and oxides of iron with no visible crystals. It was often called 'brown hematite' or 'bog iron ore'.

Field identification & locations

Identified by its yellow-brown streak (when rubbed on ceramic) and earthy appearance. Commonly found in gossans (weathered outcrops over ore bodies) and as a cementing agent in sandstones.