Chipping

One of the most disappointing failures that can happen while cutting a tourmaline gem is for the culet or keel to chip. This can happen after you have partially polished the pavilion or while cutting the pavilion. Which varieties of tourmaline are prone to chipping is hard to say, but I think really hot pink is more fragile than most colors.

Weight retention

The thickness of the preform being cut is important to how I try and remove the chips. Many times I will try and polish out the chips and not impact the thickness reserved for the crown. I use 41 degrees for the round’s mains and 40 degrees r the emerald cuts so the slight changes in angle that might occur while polishing out the chips will have no impact on the beauty of the finish gem. This preferred procedure is not always effective in removing all of the chip. Therefor a judgment decision has to be made about recutting the pavilion or not.

Judgement on chip removal

On the whole I have left some residual tiny chips and did not recut the pavilion. Conserving the thickness of the tourmaline gem is critical to both weight retention and the gems beauty (depth of tone). I also felt that I had fine ground deeply enough to get rid of any damage from coarser grinding. Therefor I was not going to get a better finish even if I ground away more material. Lately I have tried to carefully grind deeper with my dear, old, mostly worn out 3000 lap and had success in minimizing chips, in some cases. This can save a lot of polishing. And the loss of material could be unimportant.

Final point on grinding.

The discussion of grinding/polish culets and keels has left out one important point. (The following restrain in grinding is particularly important when dealing with unground surfaces on the preform which can be weaker.) I try and leave the grinding of these critical gemstone locations short of completion with each grade of coarse grinding. I try and do this even when the depth appears not to be important. Therefor the deeper grind with my final lap is just a more extreme effort of what I have been doing all along. And when done well makes beautiful gemstones.

Bruce