The Petoskey Stone, a unique and captivating fossil, holds a special place in Michigan’s natural history. This distinct stone, recognized for its intricate patterns, serves as Michigan’s official state stone. It offers a tangible connection to an ancient marine world, representing an intersection of paleontology and geology. Discovering a Petoskey Stone along the state’s shorelines links individuals to millions of years of Earth’s past.
Characteristics of the Petoskey Stone
A Petoskey Stone is fossilized rugose coral, specifically Hexagonaria percarinata. Its distinguishing feature is a pattern of tightly packed, six-sided shapes, known as corallites, the skeletal remains of individual coral polyps. These hexagonal patterns are typically more visible when the stone is wet or polished, revealing a contrast that resembles a honeycomb or sunburst. When dry, the stone often appears as ordinary limestone, ranging from light grey to beige or brown. The central “eye” within each hexagon was the coral polyp’s mouth, surrounded by radiating lines, its tentacles.
The Geological Story of Petoskey Stones
Petoskey Stones originated from colonial coral reefs that thrived in warm, shallow seas during the Devonian Period, about 350 to 400 million years ago. At that time, what is now Michigan was near the equator, providing a tropical environment for marine life. As these ancient corals died, their skeletons accumulated on the seafloor and fossilized. Over millions of years, organic material was replaced by minerals like calcite and silica, preserving the hexagonal structures within the rock. Later, during the Ice Age, glaciers scoured the landscape, breaking up fossil-bearing limestone beds and scattering the stones across Michigan’s lower peninsula.
Where to Discover Petoskey Stones
Petoskey Stones are found along the shores of Lake Michigan and Lake Huron, especially in Michigan’s northern Lower Peninsula. Key areas include beaches near Petoskey and Charlevoix. The best times to search are early spring after winter ice recedes or after storms, as wave action uncovers new stones. Since patterns are more pronounced when wet, hunting along the water’s edge or carrying a spray bottle aids identification. When collecting, respect local regulations; the Michigan Department of Natural Resources allows removing up to 25 pounds per year from state lands, but collecting is restricted in national park areas like Sleeping Bear Dunes National Lakeshore.
Michigan’s Official State Stone
The Petoskey Stone was officially designated as Michigan’s state stone on June 28, 1965. This designation, signed into law by Governor George Romney, recognized the stone’s connection to the state’s geological heritage and natural beauty. The name links to Chief Petosegay, an Odawa (Ottawa) Indian chief whose name means “rays of dawn” or “sunbeam,” fitting the stone’s radiating pattern. The stone is popular as a souvenir and plays a role in local tourism, with visitors searching for their own piece of Michigan’s ancient past.