Sedimentary
Petoskey Stone
Hexagonaria percarinata
AI-generated identification · may be incorrectHardness: 3 on Mohs scale, Color: Light brown to gray, Luster: Dull to waxy, Crystal Structure: N/A (Fossilized Coral), Cleavage: None, Specific Gravity: Variable depending on mineralization
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Physical properties
Hardness: 3 on Mohs scale, Color: Light brown to gray, Luster: Dull to waxy, Crystal Structure: N/A (Fossilized Coral), Cleavage: None, Specific Gravity: Variable depending on mineralization
Formation & geological history
Formed from fossilized rugose coral from the Devonian period, originally deposited in shallow marine environments.
Uses & applications
Used primarily in lapidary arts for cabochons, pendants, and ornamental objects. It is the state stone of Michigan.
Geological facts
Petoskey stones are actually fossilized coral, specifically Hexagonaria percarinata, which lived approximately 350 million years ago. They are distinguished by their hexagonal cell pattern.
Field identification & locations
Identified by its distinctive hexagonal pattern, commonly found along the shores of Lake Michigan and Lake Huron. Collectors often look for them wet, as the pattern becomes more visible.
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