Michigan’s state stone is a colony coral that lived in a warm Devonian sea here 350 million years ago, and it turns up as smooth grey cobbles all along the northern Lake Michigan shore, showing its six-sided cell pattern the moment it is wet. Petoskey State Park and the beaches from Charlevoix to Traverse are the classic ground; hunt the wet line after a storm. PUBLIC beaches: Michigan allows collecting up to 25 pounds a year of rock and mineral from state land, but NOT from national lakeshores such as Sleeping Bear.
Fossil coral (Hexagonaria)
Other places on the map within a couple of hours.
