sedimentary
Septarian Nodule
Septarian Concretion
AI-generated identification · may be incorrectHardness of 3.5 to 4 on the Mohs scale. Composed of calcite, aragornite, and limestone with brown, yellow, and grey colors and a dull to earthy luster.
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Physical properties
Hardness of 3.5 to 4 on the Mohs scale. Composed of calcite, aragornite, and limestone with brown, yellow, and grey colors and a dull to earthy luster.
Formation & geological history
Formed in sedimentary mudstone layers during the Cretaceous period approximately 50 to 100 million years ago through the dehydration and cracking of mud concretions.
Uses & applications
Popular as a decorative stone, polished display specimen, carved into spheres or bookends, and collected by mineral enthusiasts.
Geological facts
The distinctive crack patterns form when mud balls dry out and shrink from the inside out, creating cavities that later fill with minerals like calcite.
Field identification & locations
Easily identified by its characteristic turtle-shell pattern of internal cracks filled with contrasting minerals. Found globally, notably in Madagascar and Utah, USA.
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