mineral
Limonite (often after Pyrite)
Limonite (FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull/Earthy to sub-metallic; Crystal structure: Amorphous; Streak: Yellow-brown; Specific Gravity: 2.7-4.3
- Hardness
- 4-5
- Color
- Yellowish-brown to dark brown
- Luster
- Dull/Earthy to sub-metallic
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Physical properties
Hardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull/Earthy to sub-metallic; Crystal structure: Amorphous; Streak: Yellow-brown; Specific Gravity: 2.7-4.3
Formation & geological history
Secondary mineral formed from the chemical weathering of iron-rich minerals such as pyrite, magnetite, and siderite. Often found in oxidized zones of ore deposits and as bog iron.
Uses & applications
Historically used as an iron ore; currently used as a pigment (ochre) for paints and dyes. Small specimens are collected for geological study.
Geological facts
Limonite is not a true mineral but a mixture of hydrated iron oxides. It is responsible for the yellowish-brown coloring in many soils and weathered rock surfaces.
Field identification & locations
Identify by its characteristic yellow-brown streak and earthy appearance. Commonly found in sedimentary ironstones and as 'gossans' over mineral veins. Check for pseudomorphs after cubic pyrite.
