Diamond or Oxide Polish?

I get asked this question on a frequent basis. Here are my opinions and what I have found through many years experience works best for me.

Before I get going on the answer I need to be clear about what I cut. This is important because of course what you cut is a deciding factor in what you need to polish with.

I cut almost exclusively natural gemstones. The majority of natural gemstones with the notable exception of Sapphire and Chrysoberyl, are easily polished with either aluminia oxide or cerium oxide.

Note: Diamonds tend to work best on hard stones, 8 hardness and above. Diamonds are much more problematic on softer stones, below 8 hardness.

Stones I typically polish with CeO2 - Amethyst, Citrine, Ametrine, Rose Quartz, Crystal Quartz, Smokey Quartz, Aquamarine, Helidore, Emerald, Goshenite, Morganite, Sunstone, Feldspar, Bytownite.

Stones I polish with CeO2 but I rarely cut - Labadorite, Orthoclase, Opal, Moldavite, Andalucite, Apatite, Chrome Diopside, Flourite, Iolite, Scapolite, Sphene, Spodumene, Rhodochrosite, Zincite.

Stones I typically polish with Alumminum Oxide (Al2O3) - Garnets of all types (Almandine, Demantoid, Spessertite, Pyrope, Grossular, Uviorite), Peridot, Tanzanite, Tourmaline of all types (Achroite, Dravite, Elbiate, Indicolite, Rubellite, Schorl, Siberite, Verdelite), Zircons, Spinels.

Stones I polish with Alumminum Oxide but I rarely cut - Idocrase, Topaz

Natural stones I cut that require diamonds to polish - Sapphires (of all types), Chrysoberyl, Danburite.

Note: Most other man-made materials can easily be polished with either Alumminum Oxide or CeO2. Like I said I do not cut man-made materials, but CZ, Corundum, and larger Spinels would require diamonds to polish.

There are some exceptions and some stone types that I do polish with diamonds depending on the individual stone and the size of the stone. Often as some stones get larger (depending on the stone type) they may require diamonds to polish. The stone types I occasionally polish with diamonds are Topaz, Zircon, Danburite, Spinels, and occasionally just a problem stone/facet that I try diamonds on.

Why oxides?

As you may have noticed that I prefer to polish almost all the stones I cut using either CeO2 or Alumminum Oxide .

I know there are some people that for one reason or another like diamonds on various laps ceramic, tin (Batt is a tin lap), copper. I frankly am not a fan and do not generally agree with them.

Polishing can be done many different ways and to some extent it is each to their own and what ever works for you.

But I have found over the years that oxides are just much better than diamond polishes and work better for various reasons on most natural gem stones. This is of course my opinion. But I have a lot of experience and have at one time or another tried almost every combination of laps/polishes that are around.

Oxides just work faster and easier in my opinion. I generally find the finish that CeO2 or Alumminum Oxide leaves is much higher quality than most diamond polishes. Remember that most oxides are .3 micron or higher which roughly translates to 150,000 mesh. Many oxides depending on the manufacturer and the quality are quite a bit finer than .3 micron.

A typical diamond polishing scenario would be to cut the stone to 1200 grit, then switch to diamond prepolish and polish. Generally the steps would average some thing like this, 3,000 (for a large stone), 8,000, 14,000 (not always used), 50,000. Some people may polish to 100,000 diamond but generally people do not go much higher than 50,000 on an average diamond polish.

A typical oxide polish (for me) is cut the stone to a worn 1200 grit lap. Polish with either CeO2 or Alumminum Oxide depending on the stone... That is it, done.

Note: I am not talking about contest cutting where a slow diamond polish is easier to control for meets under high power. I would note though that many of the contest stones are "kiss" polished with an oxide after the diamond polish to give them a final "pop".

Noticed huh? Oxides are much faster and frankly I think in most cases leave a better finish. Instead of a minimum of 2 steps (many stones require 3-4 extra polish stages with diamonds) for a diamond polish. Oxides are one step.

Remember on every step/polish you will have to cut/polish every facet on the entire stone. If the stone has say 100 facets, with diamond polish you will be polishing 100 extra facets (8,000, 50,000 diamond polish, remember the oxide polish is one stage).

Depending on the stone and the diamond polishing steps the stone requires you maybe using up to 5 extra polishing stages. That would be 400 extra facets (remember the the oxides stage is one).

Think of the hours that 2-5 extra diamond polishing stages will take... Oxides are a much easier way and in my opinion a better polish for stones that can be polished with oxides.

OK... Laps and polish combinations.

Spectra Ultralaps - For a beginner or some one who does not cut a lot of stones Spectra Ultralaps that are charged with which ever oxide is needed for the stone being polished work well and they are inexpensive. They will actually polish nice flat facets if used properly. A light tough and a good prepolish are the secrets that prevent rounding.

Note: I know several guild contest winners that use Ultralaps to pop their stones before sending them off to be judged. Some of them will not admit it because they do not want people to know what they are doing. But they are using them.

Tin Laps - A tin lap is an all around work horse of a lap and will polish well with any type of oxide. Tin laps polish about as fast or faster than any other lap for Tourmaline and Garnets (once broken in). The lap I probably use the most is a tin lap with Alumminum Oxide. Mainly because I tend to cut a lot of Tourmaline and Garnets. Tin laps are also generally the laps I use to polish with diamonds (one 8,000 and one 50,000 charged tin lap) because Zinc laps are no longer available.

Note: There are various manufacturers of tin laps. Some manufacturers say their laps are made with a different processes and claim their laps are better than others. I have no personal evidence either way... What ever works as far as I am concerned. I have no real opinion, I think any manufacturer's tin lap will work fine and have used all of them at one time or another.

Phenolic Laps - These laps work very well with all oxides and I am finding that I like them and tend to use them a lot. I do not recommend a Phenolic lap for a new cutter (ultralaps for a new cutter) because they can be a little fussy about lining a facet up to be polished. But I have had very good success with them and do recommend them for a more advanced cutter that wants to polish with oxides (they are very inexpensive too). Phenolic laps are not quite as fast or easy to polish with as a good tin lap. But I do find that they help solve some occasional polishing problems that I have and they do polish almost as fast and in some cases better than a tin lap.

I realize there are some people that for one reason or another prefer diamonds to polish with. If that is the case then each to their own. This article is not really written for them, this article is for the more inexperienced faceter. I want people to try different polishes and combinations. On some venues it is easy to get the impression that diamond polish is the only, or best way to go.

But that is not necessarily true and there is a large contingent of faceters quietly using oxides and not saying anything. I personally think that if you counted what people are polishing with you would find that diamond polishes would come out a poor second in choice, at least for materials that do not require diamonds because of hardness.

Note: Every pro I know, including myself uses oxide polishes extensively. That should tell you some thing.

I would point out one last thing. Did you ever notice all the people talking on the lists like the USFG list about how they are having trouble with their charged diamond polishing laps? Notice how often they talk about how to clean them? Get them to stop scratching? Recharge them? Resurface them? Just trying to fix them in general?

Every hear or read anybody having those problems with an oxide polishing lap? That should tell you some thing.

Oxides, in particular Alumminum Oxide and CeO2 are really some of the best polishes available to faceters and if you are not using them you are really missing a much faster and easier way to polish most natural gem stones. I would also add a much more trouble free way of polishing.

To some extent polishing methods depend on what you cut and the person. But I can tell you I would not do with out my Alumminum Oxide and CeO2 oxide polishes.

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