sedimentary
Fossil Coral (Favosites Honeycomb)
Favosites (Genus), Phylum Cnidaria, Class Anthozoa
Hardness: 3 on Mohs scale (if calcified) to 7 (if silicified/agatesized); Color: Gray, tan, or white; Luster: Dull to waxy; Structure: Tabulate honeycomb-like cells (corallites); Cleavage: None (fractures irregularly); Specific Gravity: 2.6-2.8.
- Color
- Gray, tan, or white
- Luster
- Dull to waxy
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Physical properties
Hardness: 3 on Mohs scale (if calcified) to 7 (if silicified/agatesized); Color: Gray, tan, or white; Luster: Dull to waxy; Structure: Tabulate honeycomb-like cells (corallites); Cleavage: None (fractures irregularly); Specific Gravity: 2.6-2.8.
Formation & geological history
Formed through the fossilization of marine coral colonies in shallow tropical seas. These specimens typically range from the Ordovician to the Permian periods (approx. 450 to 251 million years ago). The organic material is replaced by minerals like calcite or silica over millions of years.
Uses & applications
Used primarily as decorative collector specimens, educational fossils, and occasionally cut into cabochons for jewelry (especially if silicified). In industry, limestone containing these fossils may be crushed for road base or used in cement production.
Geological facts
Commonly known as 'Honeycomb Coral' due to the closely packed polygonal cells. They were colonial animals that lived in warm, sunlit waters. Unlike modern corals, tabulate corals like Favosites lacked the complex septa (radial partitions) seen in today's coral species.
Field identification & locations
Identify in the field by looking for a 'honeycomb' or grid-like pattern on the surface of gray or tan rocks. Frequently found in limestone quarries and along shorelines in the Great Lakes region (USA) and Europe. Collectors should look for defined 'pores' or tubes on the specimen's cross-section.
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