mineral

Limonite Geode Fragment

Hydrated ferric oxide mixture (FeO(OH)nH2O)

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3.

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

Identified June 10, 2026More mineral →

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Physical properties

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to dark brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3.

Formation & geological history

Formed as an oxidation product of secondary iron-rich minerals in sedimentary deposits or as a bog iron ore. It often forms boxy or rectangular weathering structures known as ironstones.

Uses & applications

Historically used as an iron ore; currently used as a pigment (yellow ochre) and occasionally in mineral collections.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals, primarily goethite. It was once the source of 'ochre' used in prehistoric cave paintings.

Field identification & locations

Identify in the field by its distinctive yellowish-brown streak and boxy, layered, or 'boxwork' weathering patterns. Common in iron-rich sedimentary basins and weathered outcrops.

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