sedimentary
Rugose Coral (Horn Coral Fossil)
Order Rugosa (fossilized in limestone/chert)
Hardness: 3-4 (if calcite) or 7 (if silicified); Color: Tan, brown, or grey; Luster: Dull to earthy; Shape: Characteristic conical or 'horn' shape with visible septa (internal ridges).
- Hardness
- 3-4 (if calcite) or 7 (if silicified)
- Color
- Tan, brown, or grey
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (if calcite) or 7 (if silicified); Color: Tan, brown, or grey; Luster: Dull to earthy; Shape: Characteristic conical or 'horn' shape with visible septa (internal ridges).
Formation & geological history
Formed in warm, shallow marine environments. Most common specimens are from the Paleozoic Era (Ordovician to Permian periods, approx. 488 to 251 million years ago).
Uses & applications
Primarily used for educational purposes, geological research, and hobbyist collecting. Occasionally used in rustic jewelry or as garden decor.
Geological facts
Rugose corals lived as solitary polyps and were part of massive reef systems before becoming extinct during the Great Dying at the end of the Permian period.
Field identification & locations
Identify in the field by its distinct horn-like taper and the circular ridges or radial patterns inside the cup (calice). Commonly found in limestone outcrops and creek beds across North America and Europe.
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