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Last summer my wife and I took a side trip on our way to Mackinac Island to hunt for Petoskey stones along the shores of Lake Michigan at Little Traverse Bay.Petoskey stones are a fossilized rugose coral, Hexagonaria percarinata, found in the Gravel Point Formation of the Traverse Group from the Devonian era.Glaciers deposited chunks of this coral that were subsequently rounded by wave action. When dry, the stone resembles ordinary limestone but when wet or polished using lapidary techniques, the distinctive mottled pattern of the six-sided coral fossils emerges. I hand polished this piece and had it set in a pendant by a local jeweler. Another form of fossilized corals are also found in the same location,Charlevoix stones.Charlevoix stones are Favosites an extinct kind of tabulate coral. While hunting for Petoskey stones I found this Actinostroma. Apparently these stromatoporoids are common but I thought that this one was a well preserved specimen.