sedimentary
Septarian Nodule
Septarian Concretion (Calcium Carbonate/Aragonite/Calcite)
Hardness: 3.5-4 (Mohs); Color: Grey, black, yellow, brown; Luster: Dull to waxy; Crystal structure: Trigonal/Orthorhombic; Features radial cracks.
- Hardness
- 3
- Color
- Grey, black, yellow, brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 3.5-4 (Mohs); Color: Grey, black, yellow, brown; Luster: Dull to waxy; Crystal structure: Trigonal/Orthorhombic; Features radial cracks.
Formation & geological history
Formed during the Cretaceous period (50-70 million years ago) through the accumulation of minerals around a center in marine environments, followed by shrinkage cracking and mineral infilling.
Uses & applications
Primarily used for ornamental purposes, lapidary art, jewelry, home decor, and educational geology specimens.
Geological facts
The name comes from the Latin word 'septum', meaning partition, referring to the cracks that divide the nodule. They are also known as 'Dragon Stones' due to their scaly appearance.
Field identification & locations
Look for rounded, heavy stones with 'lightning bolt' or 'cracked' patterns visible on the surface. Commonly found in Utah (USA), Madagascar, and various shoreline sites.
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