sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, Limestone)
Hardness of 3.5 to 4 on the Mohs scale, colors ranging from brown, yellow, and grey with white or clear calcite veins, dull to vitreous luster, amorphous to crystalline fracture, specific gravity around 2.6 to 2.7.
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Physical properties
Hardness of 3.5 to 4 on the Mohs scale, colors ranging from brown, yellow, and grey with white or clear calcite veins, dull to vitreous luster, amorphous to crystalline fracture, specific gravity around 2.6 to 2.7.
Formation & geological history
Formed in sedimentary environments during the Cretaceous period (roughly 50 to 100 million years ago) as mud-rich sediments accumulated and formed concretions that cracked due to dehydration or earthquakes, later filled with mineral-rich water precipitating calcite and aragonite.
Uses & applications
Used primarily as decorative lapidary material, polished display specimens, bookends, and carved into various decorative objects.
Geological facts
The word 'septarian' comes from the Latin word 'septum', meaning partition, referring to the radiating cracks or partitions inside the rock.
Field identification & locations
Easily identified by its distinctive turtle-shell-like pattern of dark concretion mud surrounded by bright yellow or white crystalline veins. Commonly found in locations such as Utah and Madagascar.
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