mineral
Limonite Concretion
Limonite (FeO·nH2O)
AI-generated identification · may be incorrectHardness: 4 to 5.5 on the Mohs scale. Color: Yellowish-brown, dark brown, or reddish-brown. Luster: Earthy to submetallic. Crystal structure: Amorphous, typically forms as botryoidal, mammillary, or stalactitic masses and concretions. Cleavage: None.
- Hardness
- 4 to 5
- Color
- Yellowish-brown, dark brown, or reddish-brown
- Luster
- Earthy to submetallic
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Physical properties
Hardness: 4 to 5.5 on the Mohs scale. Color: Yellowish-brown, dark brown, or reddish-brown. Luster: Earthy to submetallic. Crystal structure: Amorphous, typically forms as botryoidal, mammillary, or stalactitic masses and concretions. Cleavage: None.
Formation & geological history
Formed through the secondary alteration and weathering of other iron-bearing minerals and rocks, frequently found in sedimentary environments or as gossans above sulfide ore deposits.
Uses & applications
Used historically as a source of iron ore, as a yellow and brown pigment (ochre) for paints and dyes, and valued by mineral collectors for unusual botryoidal and concretionary shapes.
Geological facts
Limonite is not a true discrete mineral species, but rather a mixture of related hydrated iron oxides and hydroxides, most commonly goethite and lepidocrocite.
Field identification & locations
Easily identified by its characteristic yellowish-brown streak, earthy luster, and brownish-orange weathering crusts. Found worldwide in oxidized iron deposits and weathering zones.
