mineral
Limonite (Iron Ore)
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; 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; Cleavage: None; Specific Gravity: 2.7-4.3
Formation & geological history
Formed as a secondary mineral through the weathering and oxidation of iron-bearing minerals like pyrite, magnetite, and hematite in sedimentary environments.
Uses & applications
Historically used as an iron ore and as a pigment for ochre paint. Occasionally used in industrial purification processes.
Geological facts
Limonite is not a single mineral but a mixture of hydrated iron oxide minerals. It was the primary source of 'yellow ochre' used in prehistoric cave paintings.
Field identification & locations
Identified by its distinctive yellowish-brown streak on a porcelain plate and lack of magnetism compared to magnetite. Found in wetlands as 'bog iron'.
