mineral
Limonite Concretion / Ironstone
Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O
Hardness: 4-5.5 on the Mohs scale, Color: Brown, yellowish-brown, or reddish-brown, Luster: Earthy to submetallic, Crystal structure: Amorphous or microcrystalline (pseudomorphic often after other minerals), Specific gravity: 2.7-4.3
- Hardness
- 4-5
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Physical properties
Hardness: 4-5.5 on the Mohs scale, Color: Brown, yellowish-brown, or reddish-brown, Luster: Earthy to submetallic, Crystal structure: Amorphous or microcrystalline (pseudomorphic often after other minerals), Specific gravity: 2.7-4.3
Formation & geological history
Formed through the weathering and oxidation of iron-bearing minerals in sedimentary environments, often found in soils and bog iron deposits.
Uses & applications
Historically used as a source of iron ore, and ground into pigments (ochre). Collected by mineral enthusiasts.
Geological facts
Limonite is not a true distinct mineral species, but rather a natural mixture of related hydrated iron oxides, most commonly goethite, lepidocrocite, and jarosite.
Field identification & locations
Commonly identified by its characteristic yellowish-brown streak and earthy appearance. Found worldwide in weathered iron deposits.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
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Regolith / Silicate Mineral Aggregate
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Limonite / Goethite (Iron Ore Mineral nodule)
FeO(OH)·nH2O / FeO(OH)
mineral
Septarian Pebble
Septarian nodule / Concretion
sedimentary
Schist
Schist
Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral