sedimentary
Limonite (Iron Ore)
Hydrated ferric oxide mixture (FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4.0-5.5 | Color: Brown, yellowish-brown, ochre | Luster: Dull, earthy | Crystal Structure: Amorphous/Microcrystalline | Cleavage: None | Specific Gravity: 2.7-4.3
- Hardness
- 4
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Physical properties
Hardness: 4.0-5.5 | Color: Brown, yellowish-brown, ochre | Luster: Dull, earthy | Crystal Structure: Amorphous/Microcrystalline | Cleavage: None | Specific Gravity: 2.7-4.3
Formation & geological history
Formed as a secondary mineral through the oxidation and hydration of other iron-bearing minerals (like pyrite or magnetite) in weathered zones of ore deposits or as sedimentary bog iron.
Uses & applications
Historically used as a major ore of iron; currently used predominantly as a natural pigment (yellow ochre) in paints, dyes, and cosmetics.
Geological facts
Limonite is not a true mineral in the strictest sense but a mixture of minerals, primarily goethite. It was the source of iron for many early industrial ironworks.
Field identification & locations
Identify by its yellowish-brown streak on a porcelain plate and lack of magnetism compared to magnetite. Found globally in weathered capping of iron-rich mineral veins (gossans).
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