sedimentary
Fossilized Coral (Petoskey Stone / Favosites)
Favosites (extinct genus of tabulate coral)
Hardness: 3-4 (Mohs), Color: White to tan or grey, Luster: Dull to earthy, Crystal Structure: Hexagonal honeycombs, Composition: Calcite (CaCO3) or Silica (SiO2) if silicified.
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Physical properties
Hardness: 3-4 (Mohs), Color: White to tan or grey, Luster: Dull to earthy, Crystal Structure: Hexagonal honeycombs, Composition: Calcite (CaCO3) or Silica (SiO2) if silicified.
Formation & geological history
Formed in shallow, warm marine environments during the Devonian period, approximately 350-400 million years ago, when marine organisms were buried and replaced by minerals.
Uses & applications
Informational/educational collecting, jewelry (when polished), and decorative lapidary work. Highly valued by fossil hunters.
Geological facts
This specimen shows the characteristic honeycomb structure of Favosites, often called honeycomb coral. These organisms were colonial, building large reefs long before the age of dinosaurs.
Field identification & locations
Identify in the field by looking for a 'honeycomb' or 'grid' pattern on the surface. Commonly found in the Great Lakes region, limestone quarries, and ancient seabed deposits.
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