mineral
Limonite
FeO(OH)·n(H2O)
Hardness: 4 to 5.5 on the Mohs scale; Color: Yellow-brown, brown, or dark brown; Luster: Earthy, sub-metallic, or silky; Crystal structure: Amorphous, typically occurring as massive, mammillary, or botryoidal formations; Cleavage: None; Specific gravity: 2.7 to 4.3
- Hardness
- 4 to 5
- Color
- Yellow-brown, brown, or dark brown
- Luster
- Earthy, sub-metallic, or silky
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Physical properties
Hardness: 4 to 5.5 on the Mohs scale; Color: Yellow-brown, brown, or dark brown; Luster: Earthy, sub-metallic, or silky; Crystal structure: Amorphous, typically occurring as massive, mammillary, or botryoidal formations; Cleavage: None; Specific gravity: 2.7 to 4.3
Formation & geological history
Formed by the oxidation and weathering of primary iron-bearing minerals like magnetite, pyrite, and siderite, commonly found in sedimentary environments and gossans above sulfide deposits.
Uses & applications
Historically used as a pigment (ochre), a minor ore of iron, and commonly collected as a specimen by rockhounds.
Geological facts
Limonite is not a single mineral species, but rather a mixture of related hydrated iron oxide minerals, predominantly goethite, akaganeite, and lepidocrocite.
Field identification & locations
Can be identified by its characteristic yellowish-brown streak on an unglazed porcelain plate. Found worldwide, particularly in weathered iron ore deposits.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Soil with Mineral Detritus and Quartz Fragments
Regolith / Silicate Mineral Aggregate
sedimentary
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