fossil
Fossil Coral (Rugose Coral / Horn Coral fragment)
Rugosa (Tetracoralla) / Calcite (CaCO3)
Hardness 3 (calcite matrix); buff, light brown, and tan alternating bands showing corallite wall structure and tabulae; earthy to vitreous luster; solid fossilized structure.
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Physical properties
Hardness 3 (calcite matrix); buff, light brown, and tan alternating bands showing corallite wall structure and tabulae; earthy to vitreous luster; solid fossilized structure.
Formation & geological history
Formed through permineralization or recrystallization of Paleozoic marine solitary rugose coral skeletons during the Ordovician to Permian periods (approx. 488 to 251 million years ago).
Uses & applications
Used primarily for fossil collecting, educational displays, and occasionally polished into cabochons for mineral jewelry.
Geological facts
Rugose corals, commonly known as horn corals, were abundant solitary marine organisms in ancient shallow seas before going extinct during the End-Permian mass extinction event.
Field identification & locations
Identified by parallel fine ribs (septal or tabular cross-sections) forming distinct ridged banding on the exterior. Commonly found in Paleozoic limestone formations, stream beds, and gravel deposits in regions like the American Midwest.
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