sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
AI-generated identification · may be incorrectHardness of 3-4 on the Mohs scale, brownish-grey exterior with yellow or white calcite veins, dull to vitreous luster, amorphous nodular structure.
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Physical properties
Hardness of 3-4 on the Mohs scale, brownish-grey exterior with yellow or white calcite veins, dull to vitreous luster, amorphous nodular structure.
Formation & geological history
Formed in sedimentary mudstone layers during the Cretaceous period, approximately 50 to 100 million years ago, through the desiccation and cracking of mud concretions filled with mineral-rich water.
Uses & applications
Popular in lapidary arts for making polished display pieces, spheres, and jewelry due to their intricate spiderweb patterns.
Geological facts
The word septarian comes from the Latin word septum, meaning partition, referring to the radiating cracks inside the nodule.
Field identification & locations
Easily identified by their distinctive turtle-shell or cracked-mud exterior patterns and internal crystalline networks; frequently found in Madagascar and Utah.
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