sedimentary

Ironstone concretion (likely hematite-rich)

Ferruginous concretion; primarily iron oxides/hydroxides, commonly hematite (Fe₂O₃) and goethite (FeO(OH))

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to submetallic luster, irregularly rounded and strongly weathered; hardness typically 5–6.5, with no obvious cleavage and high specific gravity (~3–5). The surface may show botryoidal or layered growth and a reddish-brown streak.

Identified August 16, 2026More sedimentary →

Explore Ironstone concretion (likely hematite-rich) 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 minerals cement sand, clay, or organic nuclei during groundwater-driven precipitation, often in sedimentary formations; its exact age cannot be determined from the photograph. It may also be a weathered iron-rich nodule rather than a pure mineral specimen.

Uses & applications

Used mainly as a teaching or collecting specimen; hematite-rich material has historically been an iron ore and pigment source, but this small nodule has little industrial value.

Geological facts

Ironstone concretions commonly develop concentric internal layers and can form distinctive rounded shapes. A reddish streak on unglazed porcelain and attraction to a strong magnet—if magnetite is present—help distinguish varieties.

Field identification & locations

Common in sandstone, shale, laterite, and stream gravels worldwide, especially Australia, the United States, India, and the United Kingdom. Estimated value: $1–$10 for a common hand specimen; unusual shapes or locality-provenanced pieces may reach $20–$50.