sedimentary
Ironstone pebble (likely limonite/goethite-rich)
Limonite, a mixture of hydrated iron oxides; commonly dominated by goethite (α-FeO(OH))
AI-generated identification · may be incorrectBrown to dark brown, earthy-to-dull luster, irregular and rounded; hardness and crystal structure cannot be determined reliably from the image. Ironstone commonly has a fine-grained texture and no visible cleavage.
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Physical properties
Brown to dark brown, earthy-to-dull luster, irregular and rounded; hardness and crystal structure cannot be determined reliably from the image. Ironstone commonly has a fine-grained texture and no visible cleavage.
Formation & geological history
Likely formed as iron oxides precipitated or accumulated in sediments, then became compacted and rounded by weathering and transport. Such deposits form across many geological ages and environments.
Uses & applications
Iron-rich ironstone has historically been used as iron ore and pigment; this small pebble is mainly of modest collecting interest.
Geological facts
Limonite is a field term for mixtures of hydrated iron oxides rather than a single mineral species.
Field identification & locations
The rusty-brown color and dense, lumpy appearance suggest ironstone, but a photo cannot confirm composition. Common in soils, sedimentary beds, and stream gravels worldwide; a streak test may help distinguish it from other brown rocks.
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