mineral
Iron-oxide-rich weathered rock
Limonite/goethite-bearing ironstone; chiefly hydrated iron oxides, often FeO(OH)·nH₂O
AI-generated identification · may be incorrectEarthy to submetallic luster with rusty yellow, orange, brown, and black coloration; typically massive, porous, and botryoidal rather than crystalline. Hardness is about 4–5.5 Mohs, with no consistent cleavage and variable specific gravity around 3.3–4.3.
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Physical properties
Earthy to submetallic luster with rusty yellow, orange, brown, and black coloration; typically massive, porous, and botryoidal rather than crystalline. Hardness is about 4–5.5 Mohs, with no consistent cleavage and variable specific gravity around 3.3–4.3.
Formation & geological history
Forms through oxidation and hydration of iron-bearing minerals, commonly as a weathering crust, gossan, bog-iron deposit, or cavity coating. It may develop at any geological age in oxygen-rich surface environments.
Uses & applications
Used historically as an iron ore and commonly as a natural yellow-brown pigment; attractive botryoidal specimens are collected, but it is rarely used in jewelry.
Geological facts
The name “limonite” describes a mixed, poorly crystalline iron-oxide material rather than one exact mineral. A reddish-brown streak on unglazed porcelain strongly supports iron oxides.
Field identification & locations
Common in oxidized ore zones, soils, caves, and weathered basalt or sulfide deposits worldwide. Distinguish it from hematite by its generally yellow-brown streak and from rusted metal by its natural porous mineral texture.
