sedimentary

Ironstone concretion

Iron-oxide-cemented sediment, commonly goethite (FeO(OH)) and/or hematite (Fe₂O₃)

AI-generated identification · may be incorrect

Rough, irregular brown-to-rusty surface with earthy to submetallic luster; likely opaque and relatively dense. Hardness and internal structure cannot be determined reliably from the photo; ironstone is variable and may show no distinct crystals or cleavage.

Identified October 14, 2026More sedimentary →

Explore Ironstone concretion in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Forms when iron oxides cement sediment or replace material during groundwater-driven chemical precipitation; age depends on its host formation and cannot be inferred from appearance alone.

Uses & applications

Commonly collected as a geological specimen; iron-rich varieties have been used as low-grade iron ore and, historically, as pigment.

Geological facts

Ironstone can develop rounded or irregular concretions and rusty colors from oxidation of iron-bearing minerals.

Field identification & locations

Look for a heavy feel, rusty brown streak, and iron-rich cement; a fresh broken surface or streak test can help distinguish it from ordinary rock. Found in sedimentary terrains worldwide.