mineral
Limonite
Limonite (Hydrous iron oxides, predominantly Goethite FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4 to 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellowish-brown; Specific Gravity: 2.7 to 4.3.
- Hardness
- 4 to 5
- Color
- Yellowish-brown to dark brown
- Luster
- Dull, earthy, or submetallic
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Physical properties
Hardness: 4 to 5.5; Color: Yellowish-brown to dark brown; Luster: Dull, earthy, or submetallic; Crystal Structure: Amorphous or microcrystalline; Streak: Yellowish-brown; Specific Gravity: 2.7 to 4.3.
Formation & geological history
Secondary mineral formed by the oxidation and hydration of iron-rich minerals (like pyrite or magnetite) in weathering zones or sedimentary deposits.
Uses & applications
Historically used as an ore of iron; widely used as a natural pigment (ochre) in paints, dyes, and cosmetics; occasionally used in metallurgy.
Geological facts
Limonite is not a true mineral species but a field term for unidentified hydrous iron oxides. It has been used as a pigment since prehistoric times, notably in Paleolithic cave paintings.
Field identification & locations
Identify by its characteristic yellowish-brown streak and lack of cleavage. It is commonly found in 'gossans' (weathered iron caps over ore deposits) and in bog iron deposits.
