mineral
Limonite / Iron Oxide Concretion
Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O
Hardness varies on Mohs scale from 4 to 5.5, color ranges from yellowish-brown to dark brown and black, luster is earthy to submetallic, amorphous crystal structure, specific gravity is 2.7 to 4.3.
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Physical properties
Hardness varies on Mohs scale from 4 to 5.5, color ranges from yellowish-brown to dark brown and black, luster is earthy to submetallic, amorphous crystal structure, specific gravity is 2.7 to 4.3.
Formation & geological history
Forms through the weathering and oxidation of iron-bearing sulfide minerals, especially pyrite, as well as in sedimentary environments and bogs where iron precipitates.
Uses & applications
Historically used as a pigment (ochre), low-grade iron ore, and occasionally collected as geological specimens.
Geological facts
Limonite is not a true distinct mineral species, but rather a natural mixture of related iron oxides and hydroxides, most commonly goethite.
Field identification & locations
Easily identified by its characteristic yellowish-brown streak and earthy appearance. Found worldwide in weathered iron deposits and soils.
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