mineral
Iron-rich weathered rock (likely limonite/goethite concretion)
Limonite–goethite mixture; chiefly FeO(OH)·nH₂O
AI-generated identification · may be incorrectBrown to dark brown, earthy to dull luster, irregular/concretionary texture, and likely Mohs hardness about 4–5.5; specific gravity commonly 3.0–4.3, with no visible cleavage or crystal structure.
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Physical properties
Brown to dark brown, earthy to dull luster, irregular/concretionary texture, and likely Mohs hardness about 4–5.5; specific gravity commonly 3.0–4.3, with no visible cleavage or crystal structure.
Formation & geological history
Forms as secondary iron oxides and hydroxides during weathering of iron-bearing rocks or in soils, bogs, and hydrothermal environments. Its age may range from recent soil formation to ancient deposits; the photograph alone cannot establish age.
Uses & applications
Used historically as iron ore and as a natural yellow-brown pigment (ochre); attractive specimens are collected but generally have little jewelry or construction value.
Geological facts
Limonite is a field term rather than a single precisely defined mineral, commonly consisting of poorly crystalline goethite and related iron oxides. Strong reddish-brown streak and possible attraction to a magnet can support identification if hematite or magnetite is present.
Field identification & locations
Common in weathered outcrops, iron-rich soils, mines, and stream gravels worldwide. Check for a yellow-brown streak on unglazed ceramic, high density, earthy texture, and rust staining; confirmation requires testing or analysis.
