mineral
Limonite (Iron Stone/Ocher)
Limonite (FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown/black, Luster: Dull to earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.7-4.3
- Hardness
- 4
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Physical properties
Hardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown/black, Luster: Dull to earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.7-4.3
Formation & geological history
Formed by the oxidation (weathering) of iron-rich mineral deposits such as pyrite, magnetite, and hematite in sedimentary or hydrothermal environments.
Uses & applications
Historically used as a yellow and brown pigment (ocher) for cave paintings and pottery. Minor source of iron ore and a common collector specimen for educational purposes.
Geological facts
Limonite is not a 'true' mineral but a mineraloid mixture of hydrated iron oxides. It was the primary source of color for ancient human artwork dating back tens of thousands of years.
Field identification & locations
Identify in the field by its distinct mustard-yellow to rust-brown streak (powder color), earthy texture, and association with wet, oxidizing environments. Commonly found in marshy areas as 'bog iron'.
