sedimentary

Limonite Ironstone

Goethite-Limonite concretion / Iron oxide

AI-generated identification · may be incorrect

Hardness: 4 to 5.5 on the Mohs scale; Color: Yellow-brown, reddish-brown, to dark brown; Luster: Earthy to submetallic; Crystal structure: Amorphous to microcrystalline; Specific gravity: 2.7 to 4.3

Hardness: 4 to 5
Color: Yellow-brown, reddish-brown, to dark brown
Luster: Earthy to submetallic

Identified August 4, 2026More sedimentary →

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Physical properties

Hardness: 4 to 5.5 on the Mohs scale; Color: Yellow-brown, reddish-brown, to dark brown; Luster: Earthy to submetallic; Crystal structure: Amorphous to microcrystalline; Specific gravity: 2.7 to 4.3

Formation & geological history

Formed through the weathering and oxidation of iron-bearing minerals or through chemical/biochemical precipitation in sedimentary environments, often found as nodules, crusts, or concretions.

Uses & applications

Used historically as an iron ore, a pigment (ochre), and as a specimen for mineral collectors.

Geological facts

Limonite is not a distinct mineral species, but rather a natural mixture of hydrated iron oxide minerals, predominantly goethite, lepidocrocite, and quartz clays.

Field identification & locations

Can be identified in the field by its characteristic yellowish-brown streak and earthy appearance. Commonly found worldwide in weathering zones of iron deposits.