sedimentary
Fossil Coral (likely Favosites or Honeycomb Coral)
Class Anthozoa, Order Tabulata, Genus Favosites
Hardness: 3-4 (calcite) or up to 7 (if silicified); Color: Tan, gray, or white; Luster: Dull to earthy; Crystal Structure: Hexagonal or polygonal tube-like structures called corallites; Cleavage: None (fossilized)
- Hardness
- 3-4 (calcite) or up to 7 (if silicified)
- Color
- Tan, gray, or white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (calcite) or up to 7 (if silicified); Color: Tan, gray, or white; Luster: Dull to earthy; Crystal Structure: Hexagonal or polygonal tube-like structures called corallites; Cleavage: None (fossilized)
Formation & geological history
Formed in warm, shallow marine environments during the Silurian to Devonian periods (approx. 430-360 million years ago) through the permineralization of coral colonies.
Uses & applications
Primarily used as decorative display specimens, educational tools in paleontology, or sometimes cut and polished for lapidary work (jewelry).
Geological facts
Known as 'Honeycomb Coral' due to the distinctive grid-like appearance of the corallites. These extinct corals lived in colonies and were once a major part of the reef ecosystems that predated modern coral reefs.
Field identification & locations
Identify in the field by looking for a repeating honeycomb or 'pocked' pattern on water-worn stones. Frequently found in the Great Lakes region of the US (such as Michigan) and areas with limestone outcroppings.
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