sedimentary

Goethite Concretion

Goethite (FeO(OH))

Hardness: 5-5.5 (Mohs scale), Color: Dark brown to black, Luster: Dull to submetallic, Structure: Earthy or botryoidal mass, High specific gravity (~4.3)

Hardness: 5-5

Identified July 19, 2026More sedimentary →

Explore Goethite Concretion in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 5-5.5 (Mohs scale), Color: Dark brown to black, Luster: Dull to submetallic, Structure: Earthy or botryoidal mass, High specific gravity (~4.3)

Formation & geological history

Formed through the precipitation of iron-rich groundwater in sedimentary environments, often congregating around a nucleus like a leaf, shell, or sand grain during rock lithification.

Uses & applications

Primarily used as a minor iron ore; occasionally used as a source of brown ochre pigment; collected as geological curiosities.

Geological facts

These are often mistaken for meteorites due to their weight and dark color. They are also nicknamed 'ironstones' or 'Indian beads' in some regions.

Field identification & locations

Look for rounded, heavy nodules that are dark on the outside but may show ochre-orange colors when scratched or cracked. Frequently found in sandstone or shale beds.