sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
AI-generated identification · may be incorrectHardness of 3-4 on the Mohs scale. Displays a brown, yellow, and grey exterior with distinct intersecting calcite veins forming a fractured pattern.
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Physical properties
Hardness of 3-4 on the Mohs scale. Displays a brown, yellow, and grey exterior with distinct intersecting calcite veins forming a fractured pattern.
Formation & geological history
Formed in sedimentary mudstone layers 50 to 100 million years ago through the shrinkage, cracking, and subsequent mineral infilling of clay concretions.
Uses & applications
Commonly sliced, polished, and carved into display pieces, spheres, and bookends for collectors.
Geological facts
The word septarian comes from the Latin septum, meaning partition, referring to the radiating cracks that divide the nodule.
Field identification & locations
Identified by its distinctive turtle-shell-like pattern of angular veins. Frequently found in marine sedimentary deposits worldwide, notably Utah and Madagascar.
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