sedimentary
Septarian (Dragon Stone)
Septarian Concretion (SiO2 + CaCO3)
Hardness: 3.5-4 (Mohs scale); Color: Yellow (calcite), brown (aragonite), gray (limestone); Luster: Earthy to vitreous; Crystal structure: Trigonal/Orthorhombic components.
- Hardness
- 3
- Color
- Yellow (calcite), brown (aragonite), gray (limestone)
- Luster
- Earthy to vitreous
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Physical properties
Hardness: 3.5-4 (Mohs scale); Color: Yellow (calcite), brown (aragonite), gray (limestone); Luster: Earthy to vitreous; Crystal structure: Trigonal/Orthorhombic components.
Formation & geological history
Formed roughly 50 to 70 million years ago during the Cretaceous period from the solidification of mud pools as sea levels receded, creating shrinkage cracks that later filled with minerals.
Uses & applications
Primarily used for ornamental carvings, pocket stones, decorative pyramids/points, and jewelry. Highly valued by collectors for its unique 'cracked' aesthetic.
Geological facts
The name comes from the Latin word 'septum', meaning partition, referring to the cracks that divide the concretion. Their patterns are unique like fingerprints.
Field identification & locations
Identified by high-contrast yellow calcite filled cracks within a darker earthy matrix. Commonly found in Utah, USA and Madagascar. Collectors should look for vibrant crystallization in the 'veins'.
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