sedimentary

Ironstone Concretion / Hematite Nodules

Ferruginous Sedimentary Rock (primarily Hematite Fe2O3 and Goethite FeO(OH))

AI-generated identification · may be incorrect

Hardness: 5-6 on Mohs scale; Color: Reddish-brown to yellowish-ochre; Luster: Earthy to metallic; Structure: Often nodular or cylindrical; Cleavage: None; Specific Gravity: 4.5-5.3.

Hardness: 5-6 on Mohs scale
Color: Reddish-brown to yellowish-ochre
Luster: Earthy to metallic

Identified June 5, 2026More sedimentary →

Explore Ironstone Concretion / Hematite Nodules in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 5-6 on Mohs scale; Color: Reddish-brown to yellowish-ochre; Luster: Earthy to metallic; Structure: Often nodular or cylindrical; Cleavage: None; Specific Gravity: 4.5-5.3.

Formation & geological history

Formed by the precipitation of iron-rich minerals from groundwater within the pore spaces of sedimentary rocks like sandstone or shale. These often form around a nucleus (like a fossil or organic matter) during the diagenesis process, frequently in the Cretaceous or Paleogene periods.

Uses & applications

Primary source of iron ore for industrial steel production. Historically used as earth pigments (ochre). Collected by amateur geologists for their unique rounded or cylindrical shapes.

Geological facts

Small, spherical hematite concretions found on Mars, nicknamed 'blueberries,' helped scientists prove the past presence of liquid water on the red planet. Terrestrial versions are often mistaken for meteorites or fossils due to their weight and odd shapes.

Field identification & locations

Identify in the field by their high density (feel heavy for their size) and reddish-brown streak when rubbed against unglazed porcelain. Commonly found in eroded sedimentary basins and badlands.