mineral
Limonite with Goethite
Iron Hydroxide Mixture (FeO(OH)·nH2O)
Hardness: 4.0-5.5; Color: Dull yellow to dark brown; Luster: Submetallic to earthy; Crystal structure: Amorphous or microcrystalline; Streak: Yellowish-brown; Specific Gravity: 2.7-4.3
- Hardness
- 4
- Color
- Dull yellow to dark brown
- Luster
- Submetallic to earthy
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Physical properties
Hardness: 4.0-5.5; Color: Dull yellow to dark brown; Luster: Submetallic to earthy; Crystal structure: Amorphous or microcrystalline; Streak: Yellowish-brown; Specific Gravity: 2.7-4.3
Formation & geological history
Formed usually through the chemical weathering of iron-rich minerals such as pyrite, magnetite, or siderite. Common in sedimentary deposits and gossans (iron caps) above ore veins.
Uses & applications
Historically used as an iron ore and as a source of yellow ochre pigment. Currently used for environmental filtration and as a low-value collector specimen.
Geological facts
Limonite is not a 'true' mineral but a mixture of hydrated iron oxides. It was a primary source of pigment for cave paintings dating back thousands of years.
Field identification & locations
Check for its characteristic mustard-yellow to brown streak on a porcelain plate. It often forms 'rust' coatings on other minerals. Found worldwide in bog iron deposits and weathering zones.
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