sedimentary

Ironstone Concretion (Iron Oxide Pebble)

Ironstone / Goethite-Hematite Concretion (Fe2O3 / FeO(OH))

AI-generated identification · may be incorrect

Hardness 5.0 to 6.5 on Mohs scale; color ranges from dark brown and reddish-brown to dark gray/black; dull to sub-metallic luster; microcrystalline or amorphous texture with rounded, water-worn or wind-polished surface (desert varnish/patina); relatively high specific gravity (3.8-5.3).

Identified November 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of iron-bearing mineral solutions (such as hematite, goethite, or limonite) within porous sedimentary rock or soil layers, often around an organic nucleus. Subsequently weathered out and smoothed by fluvial or alluvial transport.

Uses & applications

Historically mined as low-grade iron ore; commonly collected as geological curiosities, naturally smoothed river stones, or decorative garden stones.

Geological facts

Due to their dark color, high density, and rounded, pitted surface (resembling regmaglypts), ironstone pebbles and concretions are among the most common 'meteorwrongs'—objects mistakenly identified by finders as meteorites.

Field identification & locations

Identified in the field by its dark brown to red streak on unglazed porcelain, absence of genuine fusion crust, non-magnetic or only weakly magnetic nature (unless containing magnetite), and heavy feel relative to typical silicate rocks. Frequently found in stream beds, gravel deposits, and arid sedimentary basins.