sedimentary

Ironstone Concretion (Limonite/Goethite)

Iron-rich sedimentary rock (FeOx)

AI-generated identification · may be incorrect

Hardness: 5-5.5 on Mohs scale; Color: Dark brown, rusty orange, or black; Luster: Dull to sub-metallic; Crystal Structure: Amorphous or microcrystalline; High specific gravity (heavy for its size).

Hardness: 5-5
Color: Dark brown, rusty orange, or black
Luster: Dull to sub-metallic

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 5-5.5 on Mohs scale; Color: Dark brown, rusty orange, or black; Luster: Dull to sub-metallic; Crystal Structure: Amorphous or microcrystalline; High specific gravity (heavy for its size).

Formation & geological history

Formed by the precipitation of iron oxide minerals within the pore spaces of sedimentary rocks like sandstone or shale. This typically occurs in oxygenated groundwater environments during diagenesis.

Uses & applications

Historically used as an iron ore; currently used as garden decoration, for lapidary rough, or as collectible geological curiosities.

Geological facts

These are often mistaken for meteorites because of their dark, heavy appearance and rusted exterior, a phenomenon commonly called 'meteor-wrongs.'

Field identification & locations

Identify by its weight, rusty streak, and lack of internal metallic grains. Common in weathered sandstone formations and riverbeds. Collectors value specimens with unique shapes.