sedimentary
Claystone Concretion
Septarian Concretion (Ironstone-rich)
Hardness: 3.5-4.5 (Mohs), Color: Reddish-brown to tan, Luster: Dull/Earthy, Structure: Microcrystalline with occasional septarian cracks, Specific Gravity: 2.8-3.2
- Hardness
- 3
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Physical properties
Hardness: 3.5-4.5 (Mohs), Color: Reddish-brown to tan, Luster: Dull/Earthy, Structure: Microcrystalline with occasional septarian cracks, Specific Gravity: 2.8-3.2
Formation & geological history
Formed through the precipitation of mineral cement within the spaces between sediment particles. Often found in shale or clay beds from the Cretaceous period.
Uses & applications
Used primarily as decorative collector specimens, garden ornaments, and occasionally studied in paleontology to find preserved fossils inside.
Geological facts
These are often mistaken for fossils, eggs, or meteorites due to their unusual shapes. They grow from the inside out and can range from millimeters to meters in size.
Field identification & locations
Look for rounded, bulbous shapes that contrast with the surrounding layering of sedimentary rock. Common in riverbeds and eroding clay cliffs.
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