fossil
Fossilized Coral (Petoskey Stone type)
Hexagonaria percarinata (Fossilized Rugose Coral)
Hardness: 3-4 (Mohs scale), Color: Creamy white to grey, Luster: Dull to waxy, Structure: Hexagonal or radiating septa patterns, Material: Calcite or Silica replacement
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Creamy white to grey, Luster: Dull to waxy, Structure: Hexagonal or radiating septa patterns, Material: Calcite or Silica replacement
Formation & geological history
Formed during the Devonian Period (approx. 350 million years ago) when warm, shallow seas covered much of the area. These corals were buried in sediment and fossilized over millions of years.
Uses & applications
Used for jewelry (pendants and beads), ornamental stones, paperweights, and popular collector items.
Geological facts
This is the state stone of Michigan. The unique 'eye' pattern is the fossilized skeleton of ancient coral colonies. They are most easily spotted when wet, which makes the pattern pop.
Field identification & locations
Identified by the distinct honeycombed or radial pattern on the surface. Commonly found along the shores of Lake Michigan and Lake Huron. Collectors should look for them after a storm on stony beaches.
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