mineral
Limonite
FeO(OH)·nH2O (Hydrated iron oxide-hydroxide)
Hardness: 4 to 5.5 on the Mohs scale. Color: Yellowish-brown, dark brown to blackish. Luster: Earthy, sub-metallic, or silky. Crystal Structure: Amorphous or microcrystalline (pseudomorphic after other minerals). Specific Gravity: 2.7 to 4.3.
- Hardness
- 4 to 5
- Color
- Yellowish-brown, dark brown to blackish
- Luster
- Earthy, sub-metallic, or silky
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Physical properties
Hardness: 4 to 5.5 on the Mohs scale. Color: Yellowish-brown, dark brown to blackish. Luster: Earthy, sub-metallic, or silky. Crystal Structure: Amorphous or microcrystalline (pseudomorphic after other minerals). Specific Gravity: 2.7 to 4.3.
Formation & geological history
Formed through the secondary alteration and weathering of iron-bearing minerals, commonly found in gossans, oxidation zones of ore deposits, and sedimentary bog iron environments.
Uses & applications
Historically used as a low-grade iron ore and as a natural yellow ochre pigment in paints and ceramics. Rarely used in jewelry, mostly of interest to mineral collectors.
Geological facts
Limonite is not a true distinct mineral species, but rather a mixture of related hydrated iron oxides, principally goethite, akaganeite, and lepidocrocite.
Field identification & locations
Easily identified by its characteristic yellowish-brown or rust-colored streak and earthy appearance. Commonly found worldwide where iron deposits undergo weathering.
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Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
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