sedimentary
Septarian Nodule
Septarian Concretion (Calcite, Aragonite, and Limestone)
Hardness of 3.5 to 4 on the Mohs scale, brownish exterior with yellow, white, or brown internal crystals, dull to vitreous luster, monoclinic/trigonal crystal system for the internal minerals, specific gravity around 2.6 to 2.7.
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Physical properties
Hardness of 3.5 to 4 on the Mohs scale, brownish exterior with yellow, white, or brown internal crystals, dull to vitreous luster, monoclinic/trigonal crystal system for the internal minerals, specific gravity around 2.6 to 2.7.
Formation & geological history
Formed in sedimentary rocks (often mudstones or shales) approximately 50 to 100 million years ago during the Cretaceous period, created when volcanic ash and decomposing organic matter caused mudballs to form, which then cracked as they dried and were filled with mineral-rich waters.
Uses & applications
Used primarily as decorative ornamental stone, in lapidary arts, metaphysical practices, and as collector specimens.
Geological facts
The word 'septarian' comes from the Latin word 'septem,' meaning seven, referring to the cracks that typically divide the concretion into seven or more patterns.
Field identification & locations
Easily identified by its distinctive turtle-shell-like pattern of cracked mud filled with crystalline veins. Commonly found in locations such as Utah and Madagascar.
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