Editor’s Note: Some years ago, the International Gem Society (IGS) conducted a survey of members’ polishing techniques. Here, you’ll find the results for corundum polishing. The corundum gem family includes both ruby and sapphire. Whether you’re just starting to learn the art of gem cutting or just looking for a new way to tackle a problematic gem material, we hope these results provide some useful suggestions.

For more information about the survey or to find results for more gemstones, click here.

Check out these articles for additional recommendations for polishing sapphires and polishing synthetic corundum.

Corundum Polishing Techniques

Laptype polish lubrication votes
Ceramic 50-100k diamond extender/oil 44
Tin 14-100k diamond water, vinegar/oil 13
BATT 50-100k diamond oil or water 8
Ceramic 50-100k diamond none/alcohol/other 8
Fast or Last lap 14-50k diamond oil/water 7
Copper 50-100k diamond oil 6
Cast Iron 100k diamond baby oil/kerosene/olive oil/extender 5
Ceramic 50-100k diamond water 4
Zinc 50k diamond oil 3
Corian 14k diamond oil 2
Marine Brass 50k diamond oil 2
Turbofan Corundum water 1
Plexiglass 14-100k diamond oil 1
Mirror Facet Mirror Facet water 1


  • Polishing agents and lubricants divided with a “/”, like “cerium/diamond,” means either/or.
  • Polishing agents