fossil
Fossil Coral (Rugose / Horn Coral)
Rugosa (Tetracoralla)
Hardness: 3-4 (calcite) or 6.5-7 (silicified); Color: Dark brown, gray, yellowish-tan; Luster: Dull to earthy; Structure: Cylindrical or horn-shaped with distinct internal radial septa
- Hardness
- 3-4 (calcite) or 6
- Color
- Dark brown, gray, yellowish-tan
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (calcite) or 6.5-7 (silicified); Color: Dark brown, gray, yellowish-tan; Luster: Dull to earthy; Structure: Cylindrical or horn-shaped with distinct internal radial septa
Formation & geological history
Formed in warm, shallow marine seas during the Paleozoic Era (Ordovician through Permian, ~488 to 251 million years ago) through the accumulation and permineralization of calcium carbonate skeletal structures.
Uses & applications
Used primarily for educational display, fossil collections, ornamental specimens, and studying ancient marine ecosystems.
Geological facts
Rugose corals lived solitary lives attached to the seabed and went extinct during the end-Permian mass extinction event roughly 252 million years ago.
Field identification & locations
Look for a horn-like, cone-shaped body with vertical ridges (septa) radiating from the center on the cross-section. Commonly found in limestone formations in the Midwestern United States and around ancient ocean bed regions.
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