How to Polish Petoskey Stones

Co-authored by wikiHow Staff

Last Updated: January 11, 2021 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

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.
2
Transition to sanding with 220 grit paper. 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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3
Rinse each stone and dry them with a towel. 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.
4
Repeat the aforementioned process using 400 grit paper. 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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5
Conclude the sanding with 600 grit paper. 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

1
Choose a polishing base. Using one specifically made for rock polishing is ideal. Car-finish rubbing compounds work well, too.
2
Apply the polishing base to your stones. 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
Official website for the 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.
4
Wipe them off with a cloth. Make sure the cloth is clean and dry. Using a cotton cloth is fine.

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.