sedimentary
Fossilized Coral (Petoskey Stone or similar)
Hexagonaria percarinata (Order: Rugosa)
Hardness: 3-4 (Mohs scale), Color: Cream, beige, or white when unpolished, Luster: Dull to earthy (waxy if polished), Structure: Visible radial septa and hexagonal or honeycomb-like patterns.
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Physical properties
Hardness: 3-4 (Mohs scale), Color: Cream, beige, or white when unpolished, Luster: Dull to earthy (waxy if polished), Structure: Visible radial septa and hexagonal or honeycomb-like patterns.
Formation & geological history
Formed from the fossilized remains of ancient colonial corals from the Devonian period (approx. 350-400 million years ago) in shallow marine environments.
Uses & applications
Commonly used for lapidary work, jewelry, home decor, and educational geological collections.
Geological facts
The state stone of Michigan is the Petoskey stone, which is this specific type of fossilized rugose coral. These corals were once part of a reef in a warm, shallow sea covering North America.
Field identification & locations
Look for the distinctive 'sunburst' or honeycomb pattern on the surface. These are frequently found along shorelines of the Great Lakes, especially when the stone is wet.
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