sedimentary
Fossilized Honeycomb Coral
Favosites (extinct genus of tabulate corals)
Identified by closely packed polygonal (honeycomb) tubes called corallites. Hardness: 3-4 (calcite) or up to 7 (if silicified/agatized). Color: Tan, gray, or brown. Luster: Dull to waxy. Structure: Massive colonial growth.
- Hardness
- 3-4 (calcite) or up to 7 (if silicified/agatized)
- Color
- Tan, gray, or brown
- Luster
- Dull to waxy
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Physical properties
Identified by closely packed polygonal (honeycomb) tubes called corallites. Hardness: 3-4 (calcite) or up to 7 (if silicified/agatized). Color: Tan, gray, or brown. Luster: Dull to waxy. Structure: Massive colonial growth.
Formation & geological history
Formed during the Silurian to Devonian periods (approx. 430-360 million years ago). These were marine organisms that built calcium carbonate skeletons in warm, shallow seas, which were later buried and lithified into limestone or replaced by silica.
Uses & applications
Used primarily as educational specimens, decorative garden stones, and for jewelry when agatized (such as in Michigan's Petoskey/Charlevoix stones). Valuable to paleontologists for paleoenvironmental reconstruction.
Geological facts
Favosites is an extinct genus of tabulate coral. Unlike modern corals, they lacked septa (internal radial walls), giving the tubes a hollow 'honeycomb' appearance. They were major reef-builders before the Late Devonian extinction.
Field identification & locations
Identify in the field by the distinct hexagonal or polygonal pattern on the surface, resembling a wasp nest or honeycomb. Frequently found in the Great Lakes region of North America and limestone quarries globally. Use a drop of white vinegar; if it fizzes, it is still primarily calcium carbonate.
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