First of all, congratulations, I hope she says yes. There's some things you should know, though, when out shopping for the ring, if you're into that kind of thing. The ring thing.
Here's some terms specific to diamond shopping you should be able to talk with your jeweller.
via allaboutgemstones.com
The counterpart to a blemish is the Inclusion, an internal flaw in a diamond. These can be invisible from several angles, but usually show black from overhead, due to their lack of reflectivity.
