Michigan Rockhounding
August, 2007
Report by Mike Streeter
Pictures by Chrissy & Mike Streeter


Northern Michigan

I was born in Charlevoix, in northern lower-Michigan. My Mom, sister, brother and their families live there and I try to visit as often as I can. It is fortunate for me that my family lives in a beautiful harbor town, with Lake Michigan to the west and Lake Charlevoix to the east.

Lake Michigan Beach at Charlevoix

One of the most enjoyable pastimes in Charlevoix is to hunt stones along any one of a number of public beaches. One type of rock that many people like to look for is called a Petoskey Stone. A Petoskey Stone is a fossil colonial coral that lived in the warm Michigan seas during Devonian time, around 350 million years ago. The name Hexagonaria (meaning six sides) percarinata was designated by Dr. Edwin Stumm in 1969. This type of fossil is found only in the rock strata called the Gravel Point Formation that is part of the Traverse Group only found in northern Michigan. The glaciers scooped up and deposited chunks of coral that were subsequently rounded by wave action.

Petoskey Stones can be found on beaches and in gravel pits and other areas of exposed loose rock throughout northern Michigan. Countless Tourists from far and wide spend at least part of their vacations walking the Lake Michigan shoreline looking for Petoskey Stones. Many the local shops specialize in everything Petoskey Stone, including jewelry of every description, nicknacks, paperweights, etc. As a kid in Charlevoix, I loved the beach in any weather so I guess that it was inevitable that I would start hunting Petoskeys. It didn't take long for me to broaden my search to area gravel pits that were comprised of ancient lake shore deposits. So, all these many years later, Chrissy and I continue the great Petoskey Stone hunt each time we visit Charlevoix. By the time that our three day visit was over, we had accumulated yet another bushel basket full of Petoskeys, along with a few other fossil types, including stromatolites.

Click on each specimen picture to enlarge

My Mom just happens to live next to a large gravel pit, part of which is filled with a spring-fed pond. Naturally, we like to hunt the pit for rocks during our visits. Just as with most gravel deposits, there is always plenty of Petoskeys to be found. But, on our last visit, we noticed a dark gray pile of rocks that had appeared to have been brought in from elsewhere. Upon closer inspection, it was clear to me that the rocks must have originated from the nearby limestone quarry, as they contained what I recognized to be Devonian age fossils including, brachiopods, colonial coral and bryozoa. Upon even closer examination, I noticed that some of the fossils were hollow and were lined with tiny calcite crystals.

Click on each specimen picture to enlarge

Southwestern Michigan Coast

Prior to our vacation, we arranged to rockhound with our pal, Everett Harrington, on our return trip home to North Carolina. Everett lives in very southern Michigan and agreed to lead us to a couple collecting spots in the general area. It took us four hours to make the drive from Charlevoix down to South Haven where we met up with Everett and Mom Celia. The plan for the day was to hit an area of beach south of town where septarian nodules have been found.

The weather could not have been more perfect for beach combing and swimming. Having brought along my snorkeling gear, I took the perfect opportunity to do my hunting in the water while the landlubbers worked the shoreline.

Opal wasn't quite sure what to do with herself while I was swimming back and forth. A few times, she charged out into the water to see what the heck I was doing and why I was floating right where she would have liked to have been retrieving sticks.

Since the rocks show up so much better wet and you couldn't get any more wet than on the bottom of a lake, I managed to find lots of nice rocks, including a small puddingstone that had been dragged and deposited by Pleistocene glaciers from somewhere north of what is now the Canadian border!

Click on picture to enlarge

I was in the water for only about 5 minutes before I came upon a rounded brick on which the following letters were clearly engraved: "L E O". This just happens to be Chrissy's father's name, so it was quite a coincidence to find a brick bearing his name on the bottom of Lake Michigan and we shared a good laugh when I handed it to her!

Click on picture to enlarge

After about an 1-1/2 hours of swimming, I was beginning to feel the chill of the 70-degree water and decided to join the rest of the crew on the shoreline. Everett was delighted to find a rounded brick with red cement and some pretty green slag from an unknown factory that had been placed with concrete and other man-made rock for erosion control.


By late-afternoon, we had found enough rocks to make hauling them the several hundred yards back to our vehicles a real chore.

Click on each specimen picture to enlarge

After stowing our rocks and gear and confirming our plans to visit a rock quarry near Battle Creek with Everett the next day, we headed out in search of a campground where I had reserved a spot for the next couple nights.

Report continued . . . . . . .

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