seeing as how i am now a diamond expert i  have been wondering over what a jeweler said to me recently about polish and symmetry determining how good of an overall cut the stone is...........   is it true that the polish and symmetry on a GIA report(fair, good, very good or excellent) determines how good the cut of the stone is? or, is the cut (poor,good,very good, premium, or ' signature ideal') a separate entity in and of itself? isn't it possible to have 'good' polish and 'very good' symmetry and still have an 'ideal' cut stone? or am i loosing my mind?
in my diamond quest, i found many diamond websites that specialized in these so called 'signature ideal' and 'premium' cut stones. some of these sites even suggested that polish and symmetry are not that important to the lay person because only a jeweler with equipment can really tell the difference............ why do some labs include it in there certifications? and some not? anyone want to chip in here? David?       

Hi Guys!

The problem with the titles that sellers give to cuts ( premium, super duper ideal, etc) are simply sales tools nothing more.
The reason I say this is that cut is a matter of taste.
A simple look at the history of "ideal" cuts shows what I'm talking about.
Till January 2006, when GIA came out with a "cut grade" for round diamonds, the proponents of these so called "ideal" cuts pointed to AGS who said that a well cut diamond with a table of 57% was somehow better than a well cut diamond with a 60% table.
Now, GIA's "EX" cut grade which includes both 57% as well as 60% has debunked that notion..

Re Symmetry/Polish and their relationship with overall cut quality:
Having EX polish and symmetry will not necessarily make a diamond more attractive, or well cut than one with Good Polish and symmetry. I've seen some seriously ugly diamonds with VG, or EX pol/symmetry.

As far as labs- there's really only one taken seriously on the finest stones, by dealers- that's GIA.
Hope this helps!