fossil
Petoskey Stone
Hexagonaria percarinata
Hardness: 3-4 (Mohs scale), Color: Brownish-gray, Luster: Dull to vitreous when polished, Crystal structure: Hexagonal cell patterns, Specific gravity: 2.7
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Brownish-gray, Luster: Dull to vitreous when polished, Crystal structure: Hexagonal cell patterns, Specific gravity: 2.7
Formation & geological history
Devonian period fossilized coral (approx. 350 million years ago) formed by the replacement of calcium carbonate with calcite and minerals in a shallow sea environment.
Uses & applications
Commonly used in jewelry (pendants, beads), as decorative office ornaments, and highly popular for rock collecting and lapidary art.
Geological facts
It is the state stone of Michigan. The unique 'eye' pattern is the fossilized skeleton of colonial rugose coral. The name 'Petoskey' comes from the Ottawa Indian Chief Pet-O-Sega.
Field identification & locations
Identify by looking for small, six-sided honeycomb shapes. They are most easily spotted when wet, as the pattern is obscured by a gray/white chalky surface when dry. Commonly found on beaches of Lake Michigan and Lake Huron.
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