sedimentary
Limonite Iron Concretion
Hydrated iron oxide-hydroxide, FeO(OH)·nH₂O
AI-generated identification · may be incorrectMohs hardness of 4 to 5.5, yellowish-brown to dark brown color, earthy to sub-metallic luster, amorphous crystal structure, and a yellowish-brown streak.
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Physical properties
Mohs hardness of 4 to 5.5, yellowish-brown to dark brown color, earthy to sub-metallic luster, amorphous crystal structure, and a yellowish-brown streak.
Formation & geological history
Formed through the low-temperature oxidation and weathering of iron-bearing minerals in sedimentary environments and groundwater systems.
Uses & applications
Historically used as a yellow pigment (ochre) and minor iron ore, with limited use in lapidary collections.
Geological facts
Limonite is not a true distinct mineral, but rather a mixture of related iron oxides like goethite and lepidocrocite.
Field identification & locations
Identified by its characteristic yellowish-brown streak and pitted, rust-like exterior; commonly found globally in weathered iron deposits and arid soils.
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