mineral

Limonite with Ironstone

Limonite (hydrated iron(III) oxide-hydroxides), FeO(OH)·nH2O

AI-generated identification · may be incorrect

Hardness: 4-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal Structure: Amorphous (pseudomorphous); Specific Gravity: 2.7-4.3.

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

Identified June 29, 2026More mineral →

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Physical properties

Hardness: 4-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull or earthy; Crystal Structure: Amorphous (pseudomorphous); Specific Gravity: 2.7-4.3.

Formation & geological history

Formed as a secondary mineral through the oxidation and weathering of primary iron-bearing minerals like pyrite, magnetite, and siderite in the oxidation zone of ore deposits.

Uses & applications

A major source of iron ore historically; used as a natural earthy pigment (yellow ochre) in paints and coatings.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals, mainly goethite. It has been used as a pigment by humans for over 15,000 years, seen in prehistoric cave paintings.

Field identification & locations

Identify by its characteristic yellow-brown streak, earthy appearance, and lack of cleavage. Often found in bog deposits or as caps over iron-rich veins.