mineral
Limonite (Iron Ore)
FeO(OH)·nH2O
AI-generated identification · may be incorrectHardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (no visible crystals); Cleavage: None; Specific Gravity: 2.7 to 4.3
- Hardness
- 4 to 5
- Color
- Yellowish-brown to dark brown
- Luster
- Dull, earthy
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Physical properties
Hardness: 4 to 5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal Structure: Amorphous (no visible crystals); Cleavage: None; Specific Gravity: 2.7 to 4.3
Formation & geological history
Formed as a secondary material through the oxidation or weathering of iron-rich mineral deposits (like pyrite, magnetite, or glauconite) in sedimentary environments.
Uses & applications
Historically used as a major iron ore and as a natural earth pigment (yellow ochre). Commonly used in fertilizers and for manufacturing pigments/paints today.
Geological facts
Limonite is not a true mineral in the strictest sense but a mixture of hydrated iron oxide minerals. It was the source of yellow ochre used by ancient humans in cave paintings.
Field identification & locations
Identified by its ochre-yellow streak and rusty brown appearance. Often found in bog deposits or as gossan caps over sulfide ore veins. Very common worldwide in weathered rock layers.
