KEY TAKEAWAYS:
- Petoskeys are a type of fossilized coral from around 350 million years ago.
- Petoskey stones, like the city, get their name from the Odawa leader and merchant Ignatius Petosegay.
- These fossils can be found across the Lower Peninsula and in some other Great Lakes states, though they are most common in Michigan.
What are Petoskey stones?
Petoskey stones are fossilized corals. Their scientific name is Hexagonaria percarinata. During the Devonian period, around 350 million years ago, the land that would some day be Michigan was covered in a shallow saltwater sea. It was also significantly closer to the equator, which made for warm waters where sea creatures like coral could thrive.
“So if you could think about a coral from Florida, that's what a Petoskey would have looked like back then,” explained Scot Wack, co-author of Rockhounding: A Beginner’s Guide to Rock Hunting Around Lake Michigan. Scot wrote the book with his wife Jennifer. They also own the NorthPort Trading Post—a rock shop on the Leelanau Peninsula.
The “eyes” of the Petoskey stone are actually the mouths of the coral. Over millions of years, as the climate changed and the tectonic plates shifted, the corals died and the crevices of the coral became filled with limestone and other sediment.
The origin of the word Petoskey
Before European colonization, Odawa people had lived in the area that they called Bear Creek. After white settlers move to the area, they named their settlement Petoskey after a prominent Odawa businessman and landowner in the region, Ignatius Petosegay–or Biidaasige. Many of Biidaasige’s descendants still call the region home, and the reservation of the Little Traverse Bay Band of Odawa Indians covers 336 square miles of land in nearby Emmett and Charlevoix Counties. Petoskey stones are widespread in this region. In 1965, Michigan Governor George Romney signed legislation declaring the Petoskey stone the state stone of Michigan.
Where can you find them?
Petoskey is a great place to go looking for Petoskey stones, but it’s not the only place you can find them in Michigan. They are widely distributed across Michigan’s Lower Peninsula, from Lake Michigan to Lake Huron.
“When the glaciers pushed across Michigan, they pushed southeast across Michigan, which dropped them from the Grand Traverse strata all the way across Michigan to the southeast. So the further south you go, the less you're going to get,” explained Wack.
You can find Petoskey stones in some of the surrounding Great Lakes states, though they are more common in Michigan. And you don’t even need to be near water to find one, although it makes them easier to spot.
“I've got friends that have horses north of town, and they kick them out of the pasture all the time,” said Wack. “They're a lot easier to see wet. So the shoreline is basically where you're going to go, but you can find them on gravel roads. You can find them in rock pits. They're all over the place. Once you get an eye for them, you'll see them a lot more.”
Rockhounding tips for Petoskey stones
IMPORTANT NOTE: It is illegal to take rocks from national parks like Sleeping Bear Dunes National Lakeshore or Isle Royale. So in those spots, just admire your rockhounding finds where they are and put them back when you’re done.
TIP #1: Wetter is better
The distinctive honeycomb pattern on Petoskey stones is easier to see when the stones are wet. Look for them along the water’s edge or bring a spray bottle with you if you’re hunting on drier parts of the beach.
TIP #2: Anywhere on the lakeshore is fair game
The Michigan Supreme Court ruled in 2005 that the lakeshore is public property and anyone is allowed to walk along the lakeshore up to the high water mark, even on private property. But, said Scot Wack, make sure you’re not parking your stuff in one location and that you’re respectful of the property owners.
“I usually end up trying to pick up trash if I see trash. You know, it's just common sense things that we want to preserve for, for the next group of rockhounds,” said Wack.
TIP #3: Polish your finds for a clearer pattern
Scot and Jennifer recommend training your eye to find the particular shade of gray and a circular pattern that’s common to Petoskeys. Not all Petoskey stones have a super clear pattern when you find them on the beach. But if you can find gray stones with circular pattern, you can use a hand polishing kit to see if there’s a clearer pattern underneath the top layers of sediment.
TIP #4: Be mindful of future rockhounders
Be picky about the rocks you really want to take with you. There is a yearly limit of 25 lbs for rocks gathered from land owned by the state of Michigan. And, again, taking rocks (or anything else) from national parks is strictly prohibited. The good news, Scot said, is that the supply of beach stones is constantly being refreshed as the waves move in and out.
“We want to make sure that everyone is able to see it, but there is no shortage of rocks,” said Wack. “We live on a rock. There will always be rocks here.”
TIP #5: These stones tell a story
From fossils like Petoskey stones to industrial byproducts like Leland blue, the rocks you find on the beach each tell a story about our state. Spend some time figuring out what that cool-looking rock is and learning the story behind it. You might learn something surprising about our state’s ancient history–and feel a bit of wonder about your place in it.
“You know, these are 360 million year old fossils and you're finding one on the beach. You're the first one to touch it,” Wack noted.
Other Great Lakes fossils to add to your collection
Petoskey stones aren’t the only fossilized coral that you can find along the lakeshore. Others you might be able to find along a Lake Michigan beach include Charlevoix stones (favosites), chain corals (halysites), horn corals (rugose), and pipe corals (syringopora).
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