Rock Identifier
Rugose Coral Fossil (Rugosa (Order) / Horn Coral) — fossil
fossil

Rugose Coral Fossil

Rugosa (Order) / Horn Coral

Mohs hardness around 3-4 (calcite composition), white to light gray color, dull to vitreous luster, often shows distinct radial septa and a horn-like or cup-shaped structure.

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Physical properties

Mohs hardness around 3-4 (calcite composition), white to light gray color, dull to vitreous luster, often shows distinct radial septa and a horn-like or cup-shaped structure.

Formation & geological history

Formed during the Paleozoic Era (specifically Ordovician to Permian periods, roughly 450 to 250 million years ago) when ancient marine organisms secreted calcium carbonate skeletons in warm shallow seas.

Uses & applications

Used primarily by fossil collectors, in educational displays, and occasionally in lapidary work or jewelry.

Geological facts

Also commonly known as horn corals due to their horn-like shape, they went extinct during the Permian-Triassic extinction event.

Field identification & locations

Found worldwide in sedimentary limestone deposits, often recognized by their distinctive wrinkled outer wall (rugose) and internal radial symmetry.

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