sedimentary

Septarian Nodule

Septarian Concretion (Calcium Carbonate/Aragonite/Calcite)

AI-generated identification · may be incorrect

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

Identified July 6, 2026More sedimentary →

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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.