I bought an ametrine and I think that IRL it is too light, almost transparent, especially at daytime. The stone itself is not spectacular, all beauty lies in the cut which is truly amazing. It is difficult to take pictures - the stone is very bright and there are many light reflexions on the surface. In daytime, the stone looks somewhat greyish. Uli told me that it is OK to bezel it because it just needs to be open from the front (the light has to fall on it). I wanted to bezel it in silver but now I think, gold-filled silver should work better because silver could bring out more grey.
I bought an amethyst from him which (hopefully!) is on the way from Munchen. The amethyst is darker, not too dark, but darker, and I think the cut should look better in darker stones.
My personal advice? These stones do not photograph well; they look much lighter in real life. This one, I think, is still an ametrine because it has a yellowish area in the back. If you decide to buy one, get in touch with Uli before you do so and discuss the colors. Honestly, I was expecting a darker stone, although this one should look very well in a ring or a pendant. I am no expert, I have only two of his stones, and both of the same type, but it seems that you can see the cut better in the smaller of the two stones. I would still consider buying similar stones if they can be bezeled well.
Crasru,
What are the mm measurements of both stones? The newer amethyst could still be an amethyst, only with some colour zoning, which is the slight yellowish portion in the back.