sedimentary
Concretion
Septarian Concretion
Hardness: 3-4 (Mohs scale), Color: tan, brown, black, grey, Luster: earthy to waxy, Crystal structure: microcrystalline matrix with calcite/aragonite veining, Cleavage: poor/none
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Physical properties
Hardness: 3-4 (Mohs scale), Color: tan, brown, black, grey, Luster: earthy to waxy, Crystal structure: microcrystalline matrix with calcite/aragonite veining, Cleavage: poor/none
Formation & geological history
Formed in ancient seabed sediments, often during the Cretaceous period, where mineral matter precipitates around a nucleus. Cracks develop as the sediment dries and are later filled with minerals.
Uses & applications
Used for ornamental objects, decorative bookends, metaphysical collections, and educational geological specimens.
Geological facts
The name comes from the Latin 'septum' meaning partition, referring to the cracks that divide the interior. They are often called 'Dragon Stones' due to their scaly appearance.
Field identification & locations
Identify in the field by their rounded, potato-like exterior and internal mineral-filled cracks when broken. Found commonly in Utah, Madagascar, and New Zealand.
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