sedimentary

Ironstone (limonite/goethite-rich rock)

Limonite, a mixture of hydrated iron oxides, commonly including goethite (α-FeO(OH))

AI-generated identification · may be incorrect

Rusty brown to ochre, earthy to subtly metallic luster, with irregular masses and possible nodular or layered forms. Goethite is Mohs 5–5.5; limonite’s hardness varies, and its crystal structure is not distinct because it is a mixture.

Identified October 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms as iron-bearing minerals oxidize and weather, or precipitate from iron-rich groundwater in soils and sedimentary settings. The image alone cannot establish the specimen’s age.

Uses & applications

Ironstone has been used as iron ore and natural pigment; attractive pieces are collected, but this example does not appear gem-grade.

Geological facts

“Limonite” is a field term rather than a single mineral species; goethite and related iron oxides commonly produce its yellow-brown to dark-brown colors.

Field identification & locations

The rusty, lumpy coating and earthy brown coloration suggest iron oxides, but the photo is insufficient for a definitive identification. Ironstone occurs widely in weathered soils and sedimentary deposits; a yellow-brown streak and relatively high density can help confirm it.