If you wish to just keep the ring as a single prop with the stone nice and sharp it is simple if you have UVMapper.
Bring the ring into UVMapper
Select the ring group
Map it, assign to a material
Select the stone
Under the Tools use the Verices, Split vertices by group option
Map it, assign to a material.
Save wit no options selected, I suggest adding uvs to the name.
Import that into Poser and check.

If this works for you would you please let me know.

I must remember to remember what it was I had to remember.