Petoskey Stone: Fossil Coral, Identification & Michigan Geology

Petoskey Stone is fossilized colonial coral, most commonly associated with Hexagonaria, from Devonian-age rocks of Michigan. When polished, its repeating coral structure becomes especially visible.

The signature pattern

Petoskey Stone often shows rounded to hexagonal corallites arranged across the surface. The internal radiating lines can become much clearer after polishing or when the stone is wet.

A real example

Our current 8.2 oz polished Michigan Petoskey Stone shows the classic fossil coral pattern across a broad polished surface.

View the 8.2 oz Petoskey Stone specimen.

Why collectors like it

Petoskey Stone combines fossil history, regional identity and lapidary appeal. It works equally well as a fossil specimen, decorative stone and teaching piece.

Explore more fossils and petrified specimens.