sedimentary
Septarian Nodule (Dragon Stone)
Septarian Concretion (CaCO3 with Calcite, Aragonite, and Limestone/Bentonite)
Hardness: 3.5-4.0 (Mohs scale), Color: Brown, tan, and yellow with dark veins, Luster: Vitreous to dull, Crystal structure: Trigonal/Orthorhombic (within veins), Cleavage: Perfect rhombohedral in calcite infill.
- Hardness
- 3
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Physical properties
Hardness: 3.5-4.0 (Mohs scale), Color: Brown, tan, and yellow with dark veins, Luster: Vitreous to dull, Crystal structure: Trigonal/Orthorhombic (within veins), Cleavage: Perfect rhombohedral in calcite infill.
Formation & geological history
Formed during the Cretaceous period (50-70 million years ago). They began as mud balls on ancient seafloors that cracked during dehydration/shrinkage, which were later filled with minerals like calcite.
Uses & applications
Primarily used as decorative display specimens, lapidary material for bookends or spheres, and in jewelry/metaphysical collecting.
Geological facts
Also known as 'Dragon Stones' due to their scaly, reptilian appearance. They are unique because they are a combination of dehydration cracks and mineral precipitation within a single sedimentary body.
Field identification & locations
Identify by the distinct 'honeycomb' or 'turtle shell' pattern of dark brown/yellow veins against a tan host rock. Common locations include Utah (USA), Madagascar, and Morocco.
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