-
Difficulty:
-
-
Terrain:
-
Size: 
(not chosen)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
These coordinates will take you to a gorgeous, but tiny, stretch of beach at Algonac State Park. While the beach is only about ¼ mile long, it’s a rockhound’s dream, for along its shore you can see marvelous samples of the Michigan state rock, the petoskey. This Earthcache is all about petoskey stones.
The stone, only found in Michigan, is a fossilized form of coral, Hexagonaria percarinata. Most often, petoskey stones are found in Michigan’s Upper Peninsula, but they’re also easy to find around the cities of Petoskey and Charlevoix. They’re quite recognizable by their mottled markings, which are easier to see when the stones are wet; otherwise they resemble smooth limestone pebbles. But how did these pretty stones end up so far south, all the way in humble Algonac State Park?
These unique stones were formed when retreating glaciers in the Devonian Period (about 350 million years ago) broke off chunks of coral, dragging them along and depositing them in various places as they receded. This process makes them smooth in appearance, and is also the reason why the majority of petoskey stones are small in size. The specimens found in locations like the one at this cache site are also smoothed and somewhat polished by the waves and sand along the shoreline. It is possible to hand-polish fine specimens of petoskey, though polishing them in a tumbler is not recommended, as the stones are very soft.
When logging this cache, please walk the beach for a moment. While heading north along the shore, about half-way up the beach, you’ll encounter a sort of landmark. This is an excellent place to pause, to stoop down, and find a petoskey (or coral) specimen or two. If you were able to find a specimen, was it a petoskey stone, or simply a chunk of fossilized coral? Do you think it's possible to distinguish between the two, and if so, how? Please describe the piece you found, and what you think the classification would be (true petoskey or pretty but non-petoskey coral). Also, if you'd like, watch the waves for a moment, and look closely at what the waves do, how they gently tumble the rocks, along the very edge of the shore. Do your specimens show the effects of being tumbled back and forth against the sand? Optionally, please include a photo of what you've found.
In a message to me, please describe the appearance of the stones at the north end of the beach (where the short, lush trees are). How do they look different than the stones you've seen further south on the beach? Hint: it has to do with size. This will help determine if you were indeed at the right beach.
Please, be gentle with the environment and only examine the samples (don't take them), and don’t litter. Also note that if you don’t have a Michigan State Parks “Passport,” you won’t be able to park in the lot nearest the park — but parking is available along the road.
Additional Hints
(No hints available.)