I put my answer here and hope that everyone will see it. Thank you all
for responding.

The rather large piece is centerstone for a diadem and I was thinking
of crystal. Perhaps needless to say, diamond is way out of my league
here. :-)

However, I found a prism in a second hand-shop that will do nicely, at
least for a prototype diadem, so my question was a bit premature. I
might return to this friendly and well informed forum in the future
for further advice and, again, thank you all for responding to my
post.

My best,

/Kjell

On Oct 29, 2:55 am, kjelleman wrote:
I wonder if there are standard measures for these. I would like to
have a "fat" Marquise, at least fat compared to what I've found when
googling around. Ideally it should fit within the figure known as
"vesica piscis", more or less. (A somewhat pointy almond or a "fat"
Marquise cut explains the figure.)

I also read about oval cuts that there is something called the bow-tie
effect. Some kind of shadow that is usually seen as an imperfect cut.
The stone I want to have made is supposed to resemble an eye. I wonder
if there is any way to use this bow-tie effect so as to give the
illusion of the eye's pupil. Any other tip on how to achieve this
would of course be greatly appreciated.

The stone is supposed to be noncolored. If the form is not 100%
correct I guess the fitting could be done in a way to make it look
more like I want it, but most of all I want the stone itself to come
as close as possible to the ideal.

/Kjell