Many gemstones of different kinds have zoning caused by different tone levels in their color. In amethyst and sapphire etc. it is not considered desirable, but with tourmaline I find it can be used to make an interesting and beautiful gemstone or at least be render unimportant in the gemstone most of the time. The use of an emerald cut with a large ratio between its width and length is normally used to enhance the differences in tone or color that exist in some tourmaline. Steep angles on the narrow ends are sometime used to minimize mixing that occurs down the long axis of the tourmaline. I don’t cut my bi, tri and graded tone emerald cuts with steep ends because it robs them of the limited amount of scintillation that is normally found in well cut emerald cuts. The use of the same angles on the ends, as the sides, leads to the reflection of the opposing colors or tone levels in the ends of the emerald cut to the other end of the gemstone. Potentially the mixing of the colors in the ends could be ugly, but I have not run into that problem.
The stone I have chosen to demonstrate graded tone in tourmaline is a great pink and flawless. The top of the stone in the picture has the darker tone level and the reflection in the bottom (I like to call it a pagoda) is the top’s reflection imposed on a very pale body. The mixing is quite stable from face up even when the stone is examined at different angles. I instruct people to turn a tourmaline unto its table and examine the gemstone in that position, to get a good picture of what its color distribution really is.
I think the photo testifies to the fact that zoning was not a problem with this tourmaline. Fortunately the crystal shape of many tourmaline is conducive to this style of cut. I have seen some really wild ratios in emerald cuts, but I don’t go to extremes, even if weight lose in cutting is larger than necessary. I will admit that generally I do not buy rough that are crystals with excessively large ratios or short stubby pieces with different colors or tone levels unless I intend to cut it in two or to cut something like a round with its table perpendicular to the principle axis.