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Three examples of Petoskey Stones [with only natural wear giving some polished look] Click on the eArt Scan to the right, in order to have it become full screen size.

This is an eArt Scan by PMNS Curator, Terrell William 'Terry' Proctor, J.D. of Petoskey stones provided by Alyce Mulder who lives in the State of Michigan

Petoskey Stones are the official Michigan State stone. Michigan has two State fossils--THE Michigan State fossil is the Mastodon but also has a State Stone, which is the Petoskey Stone. However, the Petoskey Stone is also a fossil.

So what are Petoskey Stones? They are actually pieces of Permian coral. During the Devonian Period, most of the Central U.S., including Michigan, and on up into Canada, was under a shallow sea marine environment. Coral reefs formed upon what is now Michigan.

Petoskey Stones are found in the northern part of Michigan's Lower Peninsula. They are fragmented portions of Devonian Period coral reefs. About 360 MYBP, these coral reefs developed, in what is now Michigan. There was a species of coral which developed there which contained six sides (hexagonal) which were Hexagonaria percarinata coral. This is an example of what is known as a tabulate coral, one of two main types of coral, the other being rugose "horn" corals, which together made up the reefs during much of the Paleozoic Era. Both tabulate and rugose corals were decimated near the end of the Paleozoic Era. These two forms of coral were replaced by what are known as scleractinian corals. Scleractinian corals are what are common in reef environments today.

Why are these strange stones called the Petoskey Stones?

The Petoskey stones were found in the area of a town named Petoskey. The stones were sold as souvenirs there. The name Petoskey appears to have originated late in the 18th century. Its roots stem from an Ottawa Indian legend.

From a website of the Michigan State University http://www.geo.msu.edu/geo333/petoskystone.html, a former GEO 333 student there, named Emily Teske has written this history:

According to legend, a descendant of French nobility named Antoine Carre visited what is now the Petoskey area and became a fur trader with the John Jacob Astor Fur Company. In time, he met and married an Ottawa (or Odawa) Indian princess. Carre became known to the Indians as Neaatooshing. He was eventually adopted by the tribe and made chief.
In the spring of 1787, after having spent the winter near what is now Chicago, Chief Neaatooshing and his royal family started home. On the way, the party camped on the banks of the Kalamazoo River. During the night, a son was born to the Chief. As the sun rose, its rays fell on the face of the new baby. Seeing the sunshine on his son's face, the Chief proclaimed, "His name shall be Petosegay. He shall become an important person. " The translation of the name is "rising sun," "rays of dawn," or "sunbeams of promise".

Ms. Teske continues:In the summer of 1873, just a few years before the death of Petosegay, a city came into being on his land along the bay at Bear Creek. The site was a field overgrown with June grass. Only a few nondescript buildings existed. The population was no more than 50 or 60. The city was named Petoskey, an English adaptation of Petosegay. Thus they honored someone who gave his land, name, and the heritage of "sunbeams of promise".

Today, Petoskey is a growing city with all of the comforts of modern life and an appreciation of the past. Here is where Petoskey Stones are most commonly found. For those who look, Petoskey Stones are along the beaches, inland in gravel deposits, and sold in gift shops.

How was the Petoskey stone formed?

So, what is a Petoskey stone? It is a fossil colonial coral that lived in the warm Michigan seas during the Devonian time around 350 million years ago. The name Hexagonaria (meaning six sides) percarinata was designated by Dr. Edwin Stumm in 1969 because of his extensive knowledge of fossils. This type of fossil is found only in the rock strata called the Gravel Point Formation. This formation is part of the Traverse Group of the Devonian Age.
During the Devonian time, Michigan was quite different. Geographically, what is now Michigan was near the equator. A warm shallow sea covered the State. This warm, sunny sea was an ideal habitat for marine life. A Devonian reef had sheltered clams, cephalopods, corals, crinoids, trilobites, fish, and many other life forms.
The soft living tissue of the coral was called a polyp. At the center of this was the area where food was taken in, or the mouth. This dark spot, or eye, has been filled with mud of silt that petrified after falling into the openings. Surrounding the openings were tentacles that were used for gathering food and drawing it into the mouth. The living coral that turned into the Petoskey stone thrived on plankton that lived in the warm sea.
Calcite, silica and other minerals have replaced the first elements of each cell. Each separate chamber, then, on each Petoskey stone, was a member of a thriving colony of living corals. For that reason the Petoskey stone is called a colony coral.
The picture below illustrates the six sided formation left from the living coral colonies found on the Petoskey stone. These stones are polished and therefore display the fossilization even better. However, the wind and waves and sand cause a polishing effect, and for this reason stones found on the shores of the Bay have a more polished look naturally.

However, when Petoskey stones are found inland, they are unpolished and therefore less defined.

Where can you find the Petoskey stone?

The Petoskey stone can be found anywhere in the state from the Traverse City area across the state to Alpena. They can be found in gravel pits, and on road beds. However, the biggest influx of stones are found on and around Little Traverse Bay, in the town that gave the stone it’s name, Petoskey.

Pleistocene glaciers (about two million years ago) plucked Petoskey stones from the bedrock and spread them over Michigan and surrounding areas. This is why Petoskey stones can be found in gravel pits and along beaches far from the Petoskey area.
The best time to find the Petoskey stones is early spring after the ice on Grand Traverse Bay has melted along the shore. Each year as the ice is broken up and the winds push the ice in different directions, it pushes a new crop of Petoskey stones towards the shores. The best time to find the stone in the summer is after a wind storm or a misty rain, when the wetness will make the fossil pattern of the stone more visible. However, finding a stone might require some time and patience, especially considering the influx of other tourists seeking out the stones as well!

If you would like to learn to polish Petoskey stones by hand, Ms. Teske sets out instructions on the web page shown above, http://www.geo.msu.edu/geo333/petoskystone.html. Thank you Ms. Teske for your research on these interesting stones of Michigan.