mineral
Limonite
FeO(OH)·nH2O
AI-generated identification · may be incorrectHardness: 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
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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.
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