Well here is another gemstone hot off the dop stick. The rough had a natural table that was obvious and the tables outline looked rather like a “D”. It had a moderately strong degree of dichroism with a very nice bright green a/b axis and a darker, more olive green c axis. The c axis was so dark that I opted out of cutting an oval and decided to cut an emerald cut with possibly steep ends, to isolate the darkness. Still as I rotated the rough and then began to shape an emerald cut out of it, I was getting signs that the long dimension of the gemstone to be was not oriented with the dark c axis. And it was not oriented with the a/b axis. So how was it oriented?
Since I was dealing with a smaller piece of rough, that weighed less than a gram, you have to go for retaining weigh/size or you don’t have a stone. Therefor I preceded to rough out a normal emerald cut with an orientation that suited the efficient use of the rough. I didn’t realize, until I cut the corners of the completely ground pavilion that the dark/c axis was oriented at 45 degrees to the sides of the emerald cut. I can honestly say that I had never done that before. I had ended up using a 40 degree round of facets at the keel and two more rows that were each separated by 5 degrees because the rough was darker than I would have liked. (I usually use 40 degrees, 47 degrees and 55 degrees for a three steep pavilion.)
So what did I end up with. The material did polish well, but I had a bit of a facet failure and had to recut some of the crown. I can see the bright green a/b, but the dark c axis dominates the stone,. I can see the effect of the biased c axis in a lopsided flash, but I don’t know how many people would notice it. I will have to try it out on some innocent friends without giving away the secrete. I would also never deliberately cut another gemstone to be oriented this way. But if I came across another weird piece of rough that could only give me a good yield by having the c axis diagonal, I would cut for weight. If the c axis had not been so dark, the little emerald cut would have been much more interesting.