How to Polish Petoskey Stones

Reviewed by Claudia & Angelo Zimmermann

Last Updated: April 24, 2024 References

Petoskey stones are fossil colonial coral. They were named after the city of Petoskey, Michigan. You can find them along the sandy beaches, inland in gravel deposits, and sold in gift stores throughout the state. As charming as the stones are, maintenance is needed to make them look shiny and feel smooth. Start by sanding the stones with various types of grit paper. Then, apply a polishing base to the stones.^{[1]
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Part 1

Part 1 of 2:

Sanding Away the Scratches

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1
Use a stone file to get rid of uneven areas. The objective is to remove any relatively small bumps and create an even shape. File around the entirety of your stones until satisfied.^{[2]
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- Don't worry about getting rid of the scratches.
Dampen your stones with water beforehand. Hold each stone firmly in one hand, and rub the soon-to-be polished area with a steady, circular motion. Be careful not to over-sand.^{[3]
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If you're using a bowl of water, replace it with clean water often. The scrapings will accumulate and cloud the water if you don't. Carefully examine them for scratch marks.
This step should remove scratches from the coarser paper along with any white spots. Rinse, dry, and check your stone.^{[4]
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When you think all sanding marks have been removed, sand each stone for another 5 to 10 minutes. Your stones may already look smooth and beautiful, but this paper will ensure no scratches are missed.^{[5]
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Part 2

Part 2 of 2:

Polishing Them to Perfection

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Using one specifically made for rock polishing is ideal. Car-finish rubbing compounds work well, too.
Make sure it's a small amount (size of a quarter). Ensure the corduroy or velvet piece is lightly dampened beforehand.^{[6]
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State of Michigan
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3
Polish your stones in the manner you used for sanding. Aim for a short, circular motion. Work your way from the top to the bottom.^{[7]
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- See any scratches? Return to the 400 grit paper, and repeat the sanding process. Then, continue polishing until satisfied.
Make sure the cloth is clean and dry. Using a cotton cloth is fine.

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Tips

If your stones have been rounded by running water from glaciers or waves on the beach, a lot of your initial shaping may already be complete. This will make polishing go faster.

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Grit refers to the size of grains on a sandpaper. The higher the number, the finer the grain or grit.

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Make sure the newspaper is placed directly under your Petoskey stones before you sand them. This will catch the scrapings, which you can easily discard.

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Warning

Adult supervision is needed for children involved in sanding and polishing. Make sure you carefully explain each step of instructions in an easy manner.