Alas, no - it would look like a clear (depending on inclusion) cab. There are a few (very rare) diamonds out there that have a luminous appearance to them, though I''ve only ever seen one on-line shot from another diamond board ... and now, I can''t find it! Gr ... will add it if I hunt it down.
Yes if you see it please post it here! I did find a site that uses whole uncut type diamonds ( not really cabs though) in their jewelry, but a lot of them were poor quality. Some of the designs were fun to look at though. It''s called diamondsintherough.com
Bingo! Found it in my cache, though I'm still trying to figure out *where* I found it: I just had them saved as "Opalized Diamonds" and I'm not sure if that's the title *I* gave them, or the title they came with ... nevertheless, enjoy ....
ETA: And, found the discussion, but the site won't allow a link - but googling "Opalized Diamond" should bring it up for the curious.