mineral
Limonite / Iron Oxide Concretion
FeO(OH)·nH2O (Hydrated iron oxide)
Hardness: 4-5.5 on the Mohs scale; Color: Yellow-brown, dark brown to black; Luster: Submetallic, earthy, or dull; Crystal structure: Amorphous or microcrystalline (pseudomorphic); Cleavage: None; Specific Gravity: 2.7-4.3.
- Hardness
- 4-5
- Color
- Yellow-brown, dark brown to black
- Luster
- Submetallic, earthy, or dull
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Physical properties
Hardness: 4-5.5 on the Mohs scale; Color: Yellow-brown, dark brown to black; Luster: Submetallic, earthy, or dull; Crystal structure: Amorphous or microcrystalline (pseudomorphic); Cleavage: None; Specific Gravity: 2.7-4.3.
Formation & geological history
Formed through the low-temperature oxidation of iron-bearing minerals and weathering of iron ores. It commonly precipitates in sedimentary environments, bogs, and soils.
Uses & applications
Historically used as an iron ore and pigment (ochre); currently of interest mainly to mineral collectors.
Geological facts
Limonite is not a true mineral species in the strict sense, but rather a mixture of related hydrated iron oxides and hydroxides, most commonly goethite.
Field identification & locations
Can be identified by its characteristic yellowish-brown streak and earthy to submetallic luster. Found worldwide in oxidized zones of iron deposits.
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Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
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Septarian Pebble
Septarian nodule / Concretion
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Schist
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