By Christine Lehman • Updated Mar 24, 2022
Petoskey stones are more than just beach treasures; they are fossilized colonies of colonial coral that once thrived in the Devonian seas covering northern Michigan about 350 million years ago. Recognized as Michigan’s state stone, a polished Petoskey reveals a striking hexagonal pattern that is a testament to its ancient origins.
Begin by rubbing the stone over 220‑grit sandpaper. Place the sandpaper on a flat surface and move the stone back and forth, or lay the stone on the ground and glide the sandpaper across it. Choose the method that feels most comfortable for the stone’s size. Keep the stone and paper slightly wet to reduce friction and help the grit glide smoothly. Continue until surface blemishes are removed and a smoother texture emerges.
Repeat the motion with 400‑grit sandpaper. The stone should feel noticeably smoother and any remaining coarse spots should fade. Sand until the entire surface is uniformly polished, indicating that the roughness from the previous step has been eliminated.
Use 600‑grit sandpaper for a final refinement. Continue until the stone is free of scratches and has a refined, even surface. Spend an additional 10–15 minutes at this grit to ensure optimal smoothness.
Wet a small piece of leather or velvet and sprinkle it with polishing powder. Apply the paste with short, rotating strokes over the entire stone. This process brings out a subtle shine and enhances the stone’s natural patterns.
Rinse the stone thoroughly and dry it with a soft cloth. If any dull spots or scratches remain, restart the process at Step 1 with 220‑grit sandpaper.
Polishing a Petoskey stone is a meticulous process that can be time‑intensive. Patience and careful technique are key to revealing the stone’s full beauty.
