sedimentary
Iron-rich concretion (possibly limonite/goethite)
Limonite, a mixture of iron oxyhydroxides, commonly including goethite (α-FeO(OH))
AI-generated identification · may be incorrectRough, irregular, ochre-brown to dark brown with an earthy to dull luster; likely Mohs 4–5. Exact mineral composition and hardness cannot be confirmed from the photo.
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Physical properties
Rough, irregular, ochre-brown to dark brown with an earthy to dull luster; likely Mohs 4–5. Exact mineral composition and hardness cannot be confirmed from the photo.
Formation & geological history
Iron oxides can precipitate and accumulate in sediment, forming nodules or concretions; age and formation setting cannot be determined visually.
Uses & applications
Common iron-rich concretions have little commercial value; iron oxides are used as pigments and iron ore when sufficiently concentrated.
Geological facts
“Limonite” is a field term for mixtures of hydrated iron oxides rather than one distinct mineral species.
Field identification & locations
Its rusty brown color and lumpy, earthy surface suggest an iron-rich specimen, but testing streak (typically yellow-brown) and examining a fresh break would help distinguish it from slag or other materials. Iron-rich concretions occur in many sedimentary environments worldwide.
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