fossil
Petoskey Stone
Hexagonaria percarinata
Hardness: 3.0-3.5 (Mohs scale), Color: Gray to tan when dry; reveals a distinctive six-sided coral pattern when wet, Luster: Dull to vitreous, Crystal structure: Hexagonal (calcified coral structure), Cleavage: None
- Hardness
- 3
- Color
- Gray to tan when dry
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Physical properties
Hardness: 3.0-3.5 (Mohs scale), Color: Gray to tan when dry; reveals a distinctive six-sided coral pattern when wet, Luster: Dull to vitreous, Crystal structure: Hexagonal (calcified coral structure), Cleavage: None
Formation & geological history
Formed during the Devonian Period about 350 million years ago from the fossilized remains of ancient rugose coral colonies in warm, shallow seas.
Uses & applications
Used primarily for specimens, jewelry, paperweights, and decorative lapidary arts.
Geological facts
The Petoskey stone is the state rock of Michigan. Its unique pattern is formed by the individual coral polyps. The name comes from an Ottawa Chief, Pe-to-se-ga.
Field identification & locations
Identified by the unique 'hexagon' or honeycomb pattern visible on the surface, especially when wet or polished. Best found on the shores of Lake Michigan and Lake Huron.
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