Fresh off the boat/plane this 3.47 carat standard round brilliant is the first major tourmaline I have cut in most of a year. I have cut a couple of included specimens that came with this rough, about a 13 carat crystal from Mozambique, but they did not prepare me for the challenge that lay ahead with cutting this stone. I was even more surprised by the challenge because I had already cut an emerald cut from the same discovery more than a year ago. I had not had any problems with that project.
Examining the crystal upon its arrival should have alerted me to the problems that I would have preforming the crystal. The crystal had been clipped (quickly breaking the crystal with a tool that looks like a nail clipper) and one end was clean and bright from the fresh conchodal fractures, while the other end was irregular and had been partial ground to clean up a central peak. I am sure that the grinding was done to remove/lessen the volume of flawed material, so the piece could be rated AAA (top quality clarity). I was really not too concerned about the central peak, which can be very important, because the rough was quite deep and a round stone with its table perpendicular to the c axis (principle axis) was the obvious choice in cuts.
Soon after I started grinding the cleanly fractured end as perpendicular to the principle axis of the crystal as I could, I realized that there were some fractures on one side of the nascent table that probably came from the clipping process. I had two options, one continue grinding as I was doing and just make the preform thinner or tilt the nascent table and probably retain more depth to the preform. The medium pastel tone level of the material certainly warranted a thicker preform/gemstone, but I investigated the ground/peak end before deciding on what to do. The ground peak end turned out to contain a number of significant flaws. It would be worthless and the depth of the flaws were still unknown, when I tilted the nascent table about 10 degrees off axis. The grinding of a table, in tourmaline, that is somewhat off the principle axis can be useful for other reasons than saving depth and eliminating flaws. Tourmaline does not have cleavage, but the plane that is perpendicular to the principle axis polishes significantly different (with my polishing process) than the rest of the tourmaline, in some cases. The relationship between color and polishing problems is complex and it is part of the cutting adventure to me. Most of the tourmalines do not have a significant problem with the axis of polish, but making the table exactly perpendicular to the principle axis is asking for problems. The problems do not extend to uniform color or a significant reduction in tone of the finished gemstone as long as the angle off axis is not too large. In unusual cases I have been known to cut the table at a 45 degree angle to the principle axis. If done well, with the appropriate material (open/transparent ends a must) you can produce a wider gemstone that utilizes the rough better. In my experience the finished gemstone will not be uneven in color. Because of the mixing of colors, and I am thinking of emerald cuts principle, I wouldn’t want to cut an off axis stone where mixed colors would get muddy.
After grinding the rough into a more or less round preform, I dopped the piece. It is very useful for a relatively thin preform (and this one was getting thinner) to to be dopped perpendicular to the dop. I use a high grade shellac based wax and the heat needed to cement may have caused a small fracture to form at the edge of the table. Tourmaline can be heat sensitive, but it has not been a problem in the vast majority of my rough. Now it was time to track down the cracks that radiated from the central peak. So with a very well worn 360 grit lap I made the preform thinning and thinner. The flaws not only refused to disappear, but their existence could be seen in marks on the surface of the ground surfaces. After making the girdle truly round, I switch to a well worn 1200 lap so that I would produce less subsurface damage as I continued to grind down the nascent culet. As I approached the point of no return where I would have to reduce the width/weight of the finished gemstone, the imperfections in the rough, crystallized into a bad culet. Now the little dunce cap that sat on the culet was probably less than a mm in depth, but its removal did effect my yield. At least no other marks from flaws, that might have been propagating in front of the grinding, since I had not seen them when I examined the rough, were gone.
Now one of the most painful moments in faceting is grinding down the griddle to ensure enough depth to width ratio to cut the correct angle on the pavilion and still have a good depth for the crown. I am very conservative when it comes to having a medium to thicker crown even if the tone level of the material is high. In this case I had to also deal with the minor fracture at the edge of the stone along with the depth of the crown/girdle. After leaving a minimum of depth for the girdle and crown, I realized that the flaw could not be removed from the finished gemstone without an unacceptable amount of weight loss. And it was not only weight that would be lost. The finished gemstones has a very nice medium toned pastel look and it needed a decent depth to retain this sparkly color. I did think that cutting the crown would remove a reflective side shoot of the flaw, while the remaining part of the flaw, perpendicular to the table, would not be very visible.
I wish that I could say all my problems with this piece of rough were over now that I had a reasonably clean gemstone with good integrity, but I can’t. All the main facets at the culet polished quickly and with a flat bright polish the still amazes me with tourmaline, when it is really polishing well. My first indications of problems came with the break facets near the girdle. The were developing some rippling at the tips of the breaks that are away from the girdle. It is a pain to get them flat sometimes, but it is manageable. Then I got a scratch and the scratch did not want to go away. Now some people would think that the lap had become contaminated, but I know that it is caused by the build up of waste in the polishing powder, on the stationary lap, in this case. I had been cleaning the surface of the lap periodically with a razor blade and I was unhappy that I had apparently not done it often enough in this case. Still the appearance of the scratch is not as important as its refusal to disappear. To get rid of it I had to get off the plane of the break facet and ended up over polishing the facet. Now I can reduce the break facets size by repolishing the mains, but I decided to wait until I finished the pavilion before doing the extra work. If I had more problems it might not be worth the fuss. Well everything went well until I got another scratch on a break facet. Now these scratches are amazing. They are so sharp and bright that you would think that little fairies on ice skates were dancing on your bright polished facet. I cleaned the lap and after reapplying my mixture of vinager and chelated alumina, I started polishing again. Well the stone chirped some and when I looked at the facet it was badly scratched. I played with it for a while, but it came down to regrinding the facet. No this is a delicate job, to find the facet again with a 3000 grit lap without drastically over grinding the facet. I make a trial cut without turning the machine on. It would be nice to finish the facet recut without the machine being on, but I have found that I do not get a nice surface the way with all tourmaline. Holding my breath I recut the facet under power and it was fine, but as expected a bit too big for its britches. After not having any difficulty finishing the polishing of the culet, I was faced with two break facets that were larger than I wanted. Now neither one was really bad, but since everything else polished wonderfully with good meets, I decided to repolish the associated mains. The end from this effort was the reduction in the quality of the meets around the effected facets, but with none that were too grading on my sensitivities.
After transferring the partially completed gemstone to another dop, I adjusted the hand piece so that it was level and found out that the preform had been perpendicular to the dop stick when I cut the pavilion by gently grinding the residual wax on the table to be. This was particularly important because I now had a potential depth problem with the crown and I did not want to remove any material from the crown’s depth. I decided to grind my crown mains at my standard 40 degrees even if the table would be somewhat larger, as a percentage of the girdle, than usual. With everything set to go, the crown ground easily. The break facet angles even came in about 47 degrees which is fine. Now only one thing really stood in my way to finishing beautiful gemstone. Polishing the table.
Polishing the table of a gemstone of more than a smaller size, is an interesting effort, in my polishing world. I believe that the table is the pathway to the soul of a gemstone and I am determined to not have any marks on its surface. I also do not cut any gemstones without tables. The polishing of the table on the subject of this long discussion started out wonderfully. but I soon discovered that I had not completely ground the surface flat after I made my last adjustment on the position of the table. With a thicker crown, I would have probably taken another very light cut on the table, but conservation of material was an imperative in this case. So I polished out the slightly off angle corner of the table and the going was still easy. As the polishing continues, it becomes harder to maintain good contact with the lap over the complete area of the table. This is because I never polish a table when I am right on the surface from the start, on any significantly sized tourmaline. It just doesn’t work well. The last sections of the table are the hardest to get mark free and sometimes it has come down to the last swipe the marks the table. The marks come from the mixing and solidifying of the alumina/waste paste on the lap in my opinion. The marks, which can be like the ones I describe earlier on the breaks, can be ripped deeper or just refuse to leave while the polishing is done on their plane. I have to go off the polishing plane to remove them and that leads to more registration problems with keeping the polished part of the table in contact with the lap. And as I have said this tourmaline does not like to give up its scratches.
Well the need to polish out the corner of the table to make th table flat and a less than perfectly flat lap combined with the somewhat sensitive nature of this tourmaline combined to make scratches. None of the them were very deep, but I kept having to adjust the head to polishing them out and get registration problems. Many times the rocking back and forth over the surface of the nascent table get so frustrating that a recut is in order. The new beginning is flat and with a better appreciation of the tourmaline in question success usually takes only two to three tries. But with this stone, I did not want to grind down the table, it was large enough and so I polished into the night. I would get very close and get either a mark or realized that I had produced a crease in the table because I was a little off its plane. The stone kept responding to my efforts and it was getting flatter while staying in better contact with the lap, but the hour grows late. I was also going threw a lot of polishing compound trying to keep the level of waste down in my mixture. ( you also have to reposition yourself on the lap occasionally because of the wearing down its oxide layer, which can damage the lap and mark the stone.) Finally I was very close, but I began to feel that I would have to grind down the table. Taking my maturity in hand, I did the responsible thing and went to bed. I hate to leave a table unfinished for my dreams, but tomorrow would be another day and it is usually not a problem to come back later when the passion cools and you are rested.
The next day, I was ready and determined to finish the matter. The effort took more hours of the morning and I began to think that I would have to leave a corner of the table unfinished. I would then remove it when I repolished the stars that had receded significantly because of all the polishing on the table. But just a little more and a little more and then it was done. I gave my victory gesture, that I do not do in public, to make the stone realized how I felt about the matter and move on to polish the rest of the crown with ease.
The finished product is a different shade of gold/orange that has a satisfying medium tone level. Its only flaw is a barely noticeable (you have to look for it) dark non reflective flaw at the girdle. Its flat well polished facets give the stone a tinsel like flash as they quickly and completely turn off an on to the stone’s movement in the light. It weighs 3.47 carats which is only a 25 percent yield, but not too bad for a stone that turn out to be much less than AAA. While being similar to an emerald cut I made from a piece of rough from the same discovery, it is a fine addition to the wonderful world of color in my collection.