An illusion star cut. Far more complex and more challenging than a brilliant as I had to rethink my method once the cut bases weren't all regular polygons anymore. But, with what I've learnt from doing that today, I can now do any gem with exact precision based on a cutting chart, so it's been a useful exercise.

For this one, I actually started with an extruded 48 facet base and almost literally cut the diamond face by face in MoI according to the cutting chart. I can't see any other way of doing it with the same precision. One could probably eyeball it and make something that looked nice much faster, but angles would be wrong, and so realistic ray tracing would reveal imperfections in the cut.

This one doesn't look as good in a static image. I guess it's one of those cuts that really only come into their own once the diamond is subject to constant movement.