When I started faceting tourmaline many years ago, diamond was not generally considered the best polish for tourmaline. When I got back into faceting seriously about 15 years ago, I never considered diamond as a polish for tourmaline. In part this was because of the limits of reproducibility of my platform faceter and the multiple stepped process that is needed to produce a fine finish with diamond. I also still believe that the “wet” look I crave in polishing tourmaline is best obtained by the use of oxides. In my case I have come to focus on using alumina, though tin oxide and chrome oxide can be useful. (I have not used either one recently.)
About 10 years ago, I was experiencing scratching problems with the quality of alumina I was getting and the need for control with such an aggressive polishing agent. My solution was to go to a refined product that consists of chelated alumina (alumina held in suspension by a legate (chemical radical that attaches to the alumina in more than one location). I also stopped spinning the polishing lap for greater control and to make my meets. This lead to a number of problems with maintaining the surface properties of the tin lead lap I had come to depend on. I started using vinegar to maintain an active polishing surface and rotating the lap periodically to keep the polishing surface from being scratched or even worse ripped by an interaction with the lap. I have come to think that the wearing way of the layer of oxide on the tin lead lap during polishing and the build up of waste are the two factors, that can cause damage to the polishing facet and to the lap. (I use a razor blade to periodically remove the polishing mixture when it becomes too contaminated with waste.)
With the latest standard round brilliant I just finished I am afraid that a new chapter in the “Polish Wars” is upon me. The tourmaline I am cutting is not new to me and is a nice moderately dichroic melon color. The round is moderate in size and should polish without any problems. Yet the mains began to tear as I started my routine effort to polish them. What? Regrinding and another attack of tearing. Failure?? Well it got so bad that I even ended up doing a “kamikaze” attack on one of the mains. The consists of pushing down on the facet as hard as I can, while moving it rapidly. It can remove tears that can not be handled any other way. It can also be the end of the faceting project, but that is not usually the case. Well the tourmaline did respond well to the the attack and I was able to finish all the mains. I had move some of them so much that I had to recut the breaks. Something I almost never do.
I was growing tired of the fight to cut a modest round in a stone that was significantly included, but I polished on. Well it turned out to be a piece of cake to polish even the table, in one try. This is what I had expected.. The problem with the mains would not really warrant a call to battle in the “Polish Wars” except that I have had a couple of recent problems with other tourmaline under the same conditions. One was a small round that was part of a lot from which I had already cut several stones. The yellow green round I had not finished before that small blue green one from the lot, was behaving so badly that I thought it was a beryl. (I will be having its IR checked), but now I have my doubts.
I am sure that the geometry of the facets and their location on the gemstone causes some of the tearing problems. But I have finished an included yellow round in the middle of all this war preparations and it did not have a problem. A rather long ratio emerald cut I finished in the middle of all this, also did not have any problems with polishing. So the problem is not yet completely defined and controlled, so the “Polish Wars” continues. I intended to rework the round that I thought was beryl and you will hear of any progress. Lets hope for a quick success in my continuing effort to put the best polish on tourmaline that I can.
An update and good news on the continuing Polish Wars. I recut a round that had been driving me crazy and by reducing the amount of vinegar I used and removing waste contaminated polishing powder more often, the stone polished great. And the facets were nice and flat, which gave a nice twinkle to the modest stone that has good crystal. I suspect that I had run into a few stones that had higher than average amounts of manganese. It was probably in the form of Mn+2 because the rough did not have a strong reddish component. While many pinks polish wonderfully, there are a percentage that react too strongly to the polish and refuse to be polished without undercutting shallow braided stream-like channels in the facet. I work to minimize the effect, but it is a delicate business and I fail many times to completely eliminate it. Fortunately it is usually only a problem on facets that are close to being perpendicular to the c axis, with tables being the hardest to deal with.