sedimentary

Iron-rich concretion or weathered ironstone

Goethite–hematite-rich limonite concretion (tentative)

AI-generated identification · may be incorrect

Dark reddish-brown, earthy to dull luster, fine-grained and massive, with irregular fractures and rounded weathering. Likely hardness about 4–6 Mohs and relatively high specific gravity, roughly 3.0–4.5; no visible crystals or cleavage.

Identified September 2, 2026More sedimentary →

Explore Iron-rich concretion or weathered ironstone 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-bearing minerals precipitate and cement sediments during groundwater movement and weathering, commonly producing nodules or concretions. Its exact geological age cannot be determined from the photograph.

Uses & applications

Primarily a teaching or collecting specimen; ironstone and goethite ores have historically been mined for iron, while hematite is also used as a pigment and ornamental material.

Geological facts

The red-brown color comes from hematite, goethite, and hydrated iron oxides. A reddish-brown streak on unglazed porcelain would support an iron-oxide identification.

Field identification & locations

Common in weathered soils, sedimentary formations, and iron-rich deposits worldwide, especially Australia, Brazil, India, and the United States. A magnet test, streak test, and specific-gravity comparison would help distinguish it from ordinary mudstone or slag.