sedimentary
Ironstone Concretion
Ironstone (Limonite/Goethite/Hematite mixture)
Hardness: 5-6. Color: Dark brown to black with reddish undertones. Luster: Dull to earthy. Structure: Massive/amorphous. Cleavage: None. Specific Gravity: 3.2-3.8.
- Hardness
- 5-6
- Color
- Dark brown to black with reddish undertones
- Luster
- Dull to earthy
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Physical properties
Hardness: 5-6. Color: Dark brown to black with reddish undertones. Luster: Dull to earthy. Structure: Massive/amorphous. Cleavage: None. Specific Gravity: 3.2-3.8.
Formation & geological history
Formed by the precipitation of mineral cement, typically iron oxide, within the spaces between sediment grains in sedimentary rock layers. Common in sandstone or shale formations.
Uses & applications
Primarily collected for aesthetic interest or as curios; historically used as a low-grade iron ore.
Geological facts
These are often mistaken for meteorites due to their weight and dark color, but are actually terrestrial. Sometimes they form around a fossil nucleus.
Field identification & locations
Identified by high density, reddish-brown streak, and lack of magnetism (usually). Found in stream beds, deserts, and eroding cliffs.
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