THE PETOSKY STONE

It can be assumed that most people who have visited this website have encountered, at least once in their lives, some sort of trinket or something made out of a polished Petoskey stone. But what exactly is a Petoskey stone, and why is it called what it is? Actually, in this case, legend, geology, and history are intertwined to give the definition of what the Petoskey stone actually is. The study of the geology of the Petoskey stone also gives one quite an idea of how life was in Michigan during the Devonian time.

Why is it called the Petoskey Stone?

The name Petoskey Stone likely came about because it was found and sold as a souvenir from the Petoskey area. The name Petoskey appears to have originated late in the 18th century. Its roots stem from an Ottawa Indian legend.
   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".
    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. petosky.gif (247684 bytes)

Source:  Photograph by Randy Schaetzl, Professor of Geography - Michigan State University

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!



HOW TO POLISH PETOSKEY STONES BY HAND

And now for the real fun! Petoskey stones are made up of calcite, and therefore are a good candidate for hand polishing. Calcite is soft enough so that it can be easily worked, but dense enough to take a nice polish.

WHAT YOU NEED TO POLISH THE STONES:

Petoskey stone
Sandpaper (220, 400, or 600 grit)
A thick towel or newspaper
A piece of corduroy or velvet
Polishing powder
Water

Once you have found the stone you want to polish, sand it down with the 220 the sandpaper mentioned above. After rubbing, rinse the stone down and dry it off. Examine the stone for scratch marks, and if there are any, keep on sanding! All scratch marks should be gone!  Next, sand again with 400 grit sandpaper. This should remove any coarse spots. Once again, rinse, dry and check.  Now sand the paper with the 600 grit to make sure that the stone is smooth and scratch free. When you think it looks perfect, continue sanding for another 10 minutes, just to make sure.  At this point, it is time to polish. Sprinkle the damp corduroy or velvet with polishing powder. A short, rotating rubbing will polish the stone. However, if scratches appear, start from the beginning with the 220 grit paper to remove them!  When you’re finished with the polishing, simply rinse the stone off in clean water, and dry. Now you have your own, hand polished Petoskey stone!

 

This page was created by Emily Teske, a former GEO 333 student.  Great job, Emily.

This material has been compiled for educational use only, and may not be reproduced without permission.  One copy may be printed for personal use.  Please contact Randall Schaetzl (soils@msu.edu) for more information or permissions.