mineral

Limonite (Iron-rich Gossan/Laterite)

FeO(OH)·nH2O (Hydrated Iron Oxide)

Hardness: 4 to 5.5; Color: Yellowish-brown to dark brown; Luster: Dull to earthy; Crystal Structure: Amorphous/microcrystalline; Streak: Yellow-brown.

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

Identified June 15, 2026More mineral →

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Physical properties

Hardness: 4 to 5.5; Color: Yellowish-brown to dark brown; Luster: Dull to earthy; Crystal Structure: Amorphous/microcrystalline; Streak: Yellow-brown.

Formation & geological history

Formed by the chemical weathering of iron-bearing minerals (like pyrite or magnetite) in oxidizing environments. Common in the Carolina Slate Belt as weathering products of metallic ores.

Uses & applications

Historically used as an iron ore; currently used as an earth pigment (ochre) and as a physical indicator for mineral prospecting.

Geological facts

Limonite is not a single mineral but a mixture of hydrated iron oxide minerals, primarily goethite. It often forms the 'iron hat' or gossan over buried sulfide deposits.

Field identification & locations

Identified by its distinctive yellowish-brown streak on porcelain and its earthy, rusty appearance. Very common in the red clay soils of North Carolina due to intense weathering.

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Mineral/Rock

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