A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized coral, Hexagonaria percarinata. They are fragments of a coral reef that was originally deposited during the Devonian period, about 350 million years ago. (Wikipedia) Photo by Mark Willocks.
Petoskey Stones, the state stone of Michigan, are fossilized coral resulting from glaciation and are often polished to reveal the beautiful pattern of the 6 sided coral colonies. #Geology #Petoskey_Stone #Michigan