sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, Limestone)
AI-generated identification · may be incorrectHardness 3-4 on Mohs scale, brownish-grey exterior with yellow or white crystal vugs, dull to vitreous luster, amorphous to monoclinic crystal structure.
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Physical properties
Hardness 3-4 on Mohs scale, brownish-grey exterior with yellow or white crystal vugs, dull to vitreous luster, amorphous to monoclinic crystal structure.
Formation & geological history
Formed in sedimentary mudstone during the Cretaceous period, approximately 50 to 100 million years ago, through the cracking and mineral infilling of mud concretions.
Uses & applications
Popular in lapidary arts, decorative spheres, bookends, and sought after by mineral collectors.
Geological facts
The name originates from the Latin septum, meaning partition, referring to the characteristic pattern of cracks inside the concretion.
Field identification & locations
Easily identified in the field by its turtle-like shell pattern and internal radiating cracks filled with calcite crystals. Found globally, notably in Madagascar and Utah.
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