mineral
Limonite
FeO(OH)•nH2O
Hardness: 4 to 5.5 on Mohs scale; Color: Yellow-brown, dark brown, to black; Luster: Dull, earthy, to submetallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7 to 4.3
- Hardness
- 4 to 5
- Color
- Yellow-brown, dark brown, to black
- Luster
- Dull, earthy, to submetallic
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Physical properties
Hardness: 4 to 5.5 on Mohs scale; Color: Yellow-brown, dark brown, to black; Luster: Dull, earthy, to submetallic; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 2.7 to 4.3
Formation & geological history
Formed as a secondary mineral resulting from the oxidation and weathering of various iron-bearing minerals, often in sedimentary environments, gossans, or bog iron deposits.
Uses & applications
Historically used as a pigment (ochre), a minor ore of iron, and occasionally cut and polished into ornamental stones or jewelry.
Geological facts
Limonite is not a single distinct mineral, but rather a mixture of related hydrated iron oxides and hydroxides, most commonly goethite and lepidocrocite.
Field identification & locations
Identified easily by its characteristic yellowish-brown streak. Commonly found worldwide wherever iron-rich rocks undergo weathering.
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FeO(OH)·nH2O / FeO(OH)
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