Michigan Travel · Petoskey
Petoskey stones guide: what Michigan’s state stone is, how to spot one, and the 25-pound yearly limit on state land
PETOSKEY, Mich. — The city’s namesake rock is a fossil of a colonial coral, Hexagonaria percarinata, that grew in a warm sea covering Michigan about 350 million years ago during the Devonian period, according to the Petoskey Area Visitors Bureau and state geologists. Michigan named it the state stone in 1965.
How to spot one. Dry Petoskey stones often look like plain gray limestone. Wet, they show a honeycomb of six-sided cells, each the skeleton of a single coral polyp. That is why collectors hunt in the shallows or carry a water bottle.
When. Spring and late fall, after storms churn the shoreline and ice and waves turn over fresh stones, are favorite times, and beaches are far less crowded than in summer.
Where. Beaches along Little Traverse Bay, including Petoskey State Park and the waterfront near downtown, are popular starting points, according to the visitors bureau.
The limit. Michigan rules cap the amount of rocks, minerals and fossils one person may remove from state-owned land at 25 pounds a year, total, for personal and noncommercial use, under R 299.922. Petoskey stones count toward that limit. Collecting on private land requires the owner’s permission.
Polishing. Many local shops sell polished stones and polishing kits, and hand polishing with fine sandpaper and water brings out the pattern.
Sources:
Petoskey Area Visitors Bureau, “Petoskey Stone” (fossil coral, where to look), https://petoskeyarea.com/media/petoskey-stone/
Michigan EGLE, “Rock and mineral identification” / rockhounding (state stone, Devonian fossils), https://www.michigan.gov/egle/public/learn/geology/rockhounding
Michigan Administrative Code, R 299.921 to R 299.933 (25-pound annual limit on state land), https://ars.apps.lara.state.mi.us/AdminCode/DownloadAdminCodeFile?FileName=R+299.921+to+R+299.933.pdf
Photo: Debchristiansen, “Looking For Petoskey Stones.jpg,” Wikimedia Commons, CC BY-SA 4.0, cropped and color-adjusted, https://commons.wikimedia.org/wiki/File:Looking_For_Petoskey_Stones.jpg
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