To SG Designs: What BillBedford said is true protecting the diamond and the finger is one of the reason for this hole to be there. I will add two other reason for this particular design: it helps locating the stone when I snap it in and it also prevent the diamond from being "twisted" out. This kind of setting can be "unsafe" if there is somewhere to catch the stone (or the claws) as it can make it pop out.
For buying cz stone, this website offers very cheap ones:
http://www.diamondcz.co.uk/
The one in the picture is not a cz diamond but a "simulant" from
http://www.diamondnexus.com/loose-stones in the US. Apparently it is quite different than a CZ, but I am still not convinced by the difference in price...
Finally for real diamond, as I don't like the idea of a mined diamond (neither did she by the way
), I bought a lab created diamond from Gemesis in the US to:
http://gemesis.com/diamonds/. There I can really tell the difference
(but obvioulsy there is a huge difference in price to).
Regards,
Sapro