mineral

Limonite (Iron Ore)

Limonite (Hydrous ferric oxides), generic formula FeO(OH)·nH2O

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to dark brown; Luster: Dull, earthy, or submetallic; Crystal structure: Amorphous (no visible crystal habit); Cleavage: None; Specific gravity: 2.7–4.3.

Hardness: 4-5
Color: Yellowish-brown to dark brown
Luster: Dull, earthy, or submetallic

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the secondary alteration of iron-rich minerals (like pyrite, magnetite, or hematite) via weathering and oxidation. Found in oxidized zones of iron ore deposits and as bog iron in sedimentary environments.

Uses & applications

Historically used as a major iron ore and as a pigment (yellow ochre). Today, it is used in the production of brown and yellow paints and as a low-grade iron source in industry.

Geological facts

Limonite isn't a true mineral but a 'mineraloid' as it is a mixture of several hydrous iron oxide minerals. It has been used by humans as a pigment since prehistoric times (cave paintings).

Field identification & locations

Identify in the field by its distinct yellowish-brown streak on a porcelain plate and its earthy, rusty appearance. Often found in swampy areas or as 'gossan' capping metallic ore veins. Common globally.

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