Such crystals must be oriented with table orthogonal to optic axis,
which is very detrimental to yield, but does wonders to appearance.
What I am trying to say, is that it is going to take time, and will
be quite expensive.
The above statement by Mr. Surpin is incorrect…
Ametrine is not expensive in the rough and the cutting costs of
standard shapes are similar.
The reason ametrine it is not often cut into ovals or rounds is
because the pavilion facets cause the two colours to mix, resulting
a stone that does not have a clear colour definition and looks muddy
from the top. In the case where one mixes any two opposite
colors–purple and yellow, red and green, orange and blue-- you will
get a sort of muddy brown. An emerald cut has long straight pavilion
facets, thus keeping the colours distinct and separate…
An example where I purposely want to mix the colours is in my latest
blog post. In this case I want the blue and purple to form indigo…–
which it does.
A good example of a muddy ametrine can be found here at the bottom
of the page. http://www.wsfgems.com/amethyst.html