A Petoskey stone is a rock with fossilized rugose coral (Hexagonaria percarinata). These corals lived in Michigan during the Devonian time period (between 419-358 million years ago). During this time, warm shallow seas covered much of the state. Petoskey stones can often be found in the northern region of Michigan's lower peninsula and in 1965, they were named Michigan's state stone.
Virtual Discovery Kit: Fossils (April 2020) Calling all paleontologists! Step back on the geological timeline to explore a variety of plant and animal fossils. Learn all about the science of fossils and how prehistoric creatures lived, ate, and moved about our world.