sedimentary

Ironstone Concretion

Ferruginous Sandstone / Iron-rich Sedimentary Rock

AI-generated identification · may be incorrect

Hardness: 5-6 (Mohs); Color: Dark brown, reddish-brown, or rusty; Luster: Dull, earthy; Crystal structure: Amorphous or microcrystalline; Cleavage: None; High specific gravity due to iron content.

Hardness: 5-6 (Mohs)
Color: Dark brown, reddish-brown, or rusty
Luster: Dull, earthy

Identified June 13, 2026More sedimentary →

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Physical properties

Hardness: 5-6 (Mohs); Color: Dark brown, reddish-brown, or rusty; Luster: Dull, earthy; Crystal structure: Amorphous or microcrystalline; Cleavage: None; High specific gravity due to iron content.

Formation & geological history

Formed by the precipitation of mineral cement, typically iron oxides like hematite or goethite, within the spaces between sediment grains. These often form in marshy environments or via groundwater movement through sandstone layers over millions of years.

Uses & applications

Historically used as a low-grade iron ore. Today, used primarily as decorative stones in landscaping, as a geological curiosity for collectors, and occasionally in construction as aggregate.

Geological facts

Ironstones can sometimes form 'Limonite boxworks' or hollow nodules. They are often mistaken for meteorites because of their dark, heavy, and metallic appearance, a phenomenon known as 'meteor-wrongs'.

Field identification & locations

Identify by its heavy weight relative to size and the presence of a 'rusty' yellow or red streak. Found globally in sedimentary basins, often weathering out of sandstone or shale cliffs.