I am not sure that it would do very well as a serious jewelry establishment. Diamond Finger has a rather non-serious sound to it, IMHO at least
BUT, mentioning a "finger" somehow makes me think of the "middle finger" right away, and that goes perfectly with the next thing diamonds make me think of: screwing people out of their money This would make a great site, blog type perhaps, educating potential diamond buyers about where these stones come from, how many people and nations suffer (or at least suffered), so that de Beers could make its billions. How diamonds are not even that rare and how the whole thing is mostly blown out of proportion by advertisment, false traditions and pure brainwashing... And yes, I did buy my fiance a diamond engagement ring for mid-to-high $x,xxx - unfortunately, your domain does not come even close to that at this stage...
I would say mid-$xx undeveloped if you get lucky.
Good luck!