I believe the fiber optic will be needed for very fine point source...considering some gems will be 4mm or so, some larger depending on the stone.   The white led would probably provide a good feed for the fiber.   Good thoughts!  I am handy enough to put it all together.

This shot is of a piece in progress. The photo shows problems with lighting, in this case,the gemstones are blown out from too much direct light. The metal is not very reflective at this stage of the work.

The second shot is more decent, still, we rejected this one since the center stone was a bit too lively and focus was not dead on.   Both pics are rejects but kept as reference to the job done.
I wanted to post one where the metal was great and the stone looked dead...alas, not on this pc!