mineral
Limonite (Iron-rich Gossan/Laterite)
FeO(OH)·nH2O (Hydrated Iron Oxide)
AI-generated identification · may be incorrectHardness: 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
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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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