Very nice results! Shooting jewellery is one of the hardest things I've tried. I metal detect as my other hobby and often find myself shooting rings I've found, it is more difficult than one would think to get a good result. A light box of some sort really helps.
I like the dark background in the first image, very nice. I usually use a white one but that is just because I use simple household objects for light diffusers. Plastic milk jugs work ok as do the white ice-cream buckets. I'd be interested in hearing how you get the dark background and maintain the light. Got any tips?
Oh...and don't forget to put your wife's jewellery back....