I’m frequently asked by novice gem cutters whether they should use oxide polish or diamond for polishing gemstones. I do have my opinions, based on many years of experience. First, I want to be clear about the type of materials I cut, because your gem types are a deciding factor when you’re choosing an abrasive for polishing.

Recommended Polishes For Natural Gemstones

I cut natural gemstones almost exclusively. The majority, with the notable exception of sapphire and chrysoberyl, are easily polished with an oxide polish, either aluminum oxide (Al2O3) or cerium oxide (CeO2). Diamond polish tends to work best on hard stones, hardness 8 and above. On softer stones below hardness 8, diamonds are much more problematic.

Stones Typically Polished With Cerium Oxide

Amethyst, citrine, ametrine, rose quartz, crystal quartz, smoky quartz, aquamarine, heliodor, emerald, goshenite, morganite, sunstone, feldspar, bytownite.

I rarely cut the following, but these should also be polished with cerium oxide.

Labradorite, orthoclase, opal, moldavite, andalusite, apatite, chrome diopside, fluorite, iolite, scapolite, sphene, spodumene, rhodochrosite, zincite.

Stones Typically Polished With Aluminum Oxide

Garnet