04/18/2026
Celebrating Petoskey stones! We have several in our collection. Did you know that Ella Petoskey, Chief Petoskey’s granddaughter, was present when Governor Milliken officially declared the Petoskey stone the state stone?
The official stone of Michigan, Petoskey stones were formed by glaciers pulling fossilized rugose corals from the bedrock, grinding their surfaces smooth, and depositing them along the shores of Lake Michigan. Rugose, or wrinkled, corals are an extinct type of coral, which were abundant 470 to 252 million years ago. Like many corals today, they lived on the seafloor either individually or in large colonies, and their skeletons were made of calcite. This particular coral species is found only in Michigan’s Gravel Point Formation, mostly around the town of Petoskey in the northwest portion of the lower peninsula.