Petoskey Stone Polishing Demonstrations


Our education committee provides classroom demonstrations of the polishing of Petoskey stones and tells students about our state stone, where it comes from, and what kind of fossil it is. 

 


MATERIALS:

Petoskey stone, three inches or less in diameter. If the stone is beach polished, or lightly tumbled using only sand and gravel as grit, the work will go faster.

Silicon carbide wet or dry sand paper220, 400 & 600 grits

Thick newspaper, a folded towel, or piece of rubber

Piece of cotton, corduroy or velvet

Polishing powder Tin oxide, cerium oxide or other specialized polish compound

Water

 

METHOD:

Use a thick pad (newspaper, towel or rubber) under each

piece of sandpaper and cloth.

Use a quarter sheet of sandpaper at a time.

As you are working, the sandpaper will become covered with fine bits of the stone you are polishing. You need to remove these bits every so often by 'washing' the sandpaper in a bowl or under running water.

 

1.Begin sanding with the 220 grit sandpaper. Hold a dampened stone firmly in one hand and rub the area of the stone to be polished on the sandpaper with a steady, rotating motion. After rubbing, rinse the stone and dry it. Examine for scratch marks which should be removed with more rubbing. This first sanding is very important and should be done with care.

 

2.Repeat the process using the 400 grit paper. This step should remove the scratches from the coarser paper, and any white spots. Rinse, dry and check.

 

3. If you are Using a bowl of water, dump the dirty water and get fresh.

 

4. Complete the sanding with 600 grit paper. Rinse and dry.
Examine the stone very carefully for any scratches or abrasions.
If there are any, go back to a coarser paper and repeat the process.
ALL SCRATCHES MUST BE REMOVED BEFORE POLISHING.

 

5. To polish, sprinkle a very small amount of polishing powder on the lightly dampened corduroy or velvet square. A short, rotating rub does the polishing. Lengthy rubbing does little to Improve the good polish reached quickly. If scratches show after polishing, go back to the 400 grit and work forward through the polish again.

 

6. Wipe off the stone, and you will have a beautiful petoskey, our Michigan state stone. Doing each step carefully should produce a finely polished stone, one of which you can be proud!

 

This method contributed by— Mr. Frank Rickerd

William and Bessie Rogers

Central Michigan Lapidary & Mineral Society


 

An added tip is that this proceedure will will work for most carbonate rocks.

For instance, marble, travertine and Michigan's Kona Dolomite all polish with this method