A Petoskey State of Mind

I promise, I will not use my science background to bore you too much, nor lecture on random facts, but, well, this summer I discovered a strange and amazing facet of northern Michigan. The beaches on Lake Michigan are sparsely littered with fossils of sea shells and most notably- these six sided corals called Petoskey Stones. They're even the Michigan state stone. 
I read that there was a coral reef there long (LONG) ago with a tropical sea and these are relics of that warmer time, and then I also read that these fossils made their way via an ice age and something about glaciers and bedrock, blah blah, whatever. In any case, they are there now.
Everywhere, stores were selling these Petoskeys. There was jewelry of all kinds made from these and people paying for ones found on the beach and scrreeech-halt! You mean, I can find these on the beach? Myself?! C'mon kids (or Ferb), I know what we're gonna do today!
I also know what we're doing for the Science Fair this year!  
The McCarron family has vacationed in Northern Michigan for years. An old family story is that Joan, Scott's Mom, had the hardest time finding these Petoskys. Finally, she discovered the secret. They have to be wet to be really visible. Once she found that out, she would scour the beaches, especially after a storm, and come home with a handful of them.
You can still kinda see the the coral pattern as white hexagons on the grey rocks when dry, but when wet (or polished), you can see the entire cells the ancient polyps formed. The kids LOVE to search for them, and well, so do we!
On a more lazy day of vacation (don't judge, you know you need one too), I sat in my reclining chair, lazily digging in the sand, collecting possible Petoskys. The kids would come to me, collect my rocks, run to the water, dip them in to reveal either a grey stone or a Petosky. We would scream with delight when we found one, as well, it's novel, and a cool thing to discover, no matter what age.
Here are some photos of the rocky beaches (yes, there are plenty of sandy ones too!), the kids collecting, shell and honeycomb fossils, and Petoskys!


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  • I never heard of this. I want to hunt for some next time I'm in MI.

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