Tiffany prides itself on its cut. So are all Tiffany diamonds rated "ideal"?
My understanding is that 'ideal' or 'signature ideal' is kind of a made up grade with different qualifiers and definitions for different vendors. (GIA certificates, for example only go up to Excellent). While I do think that Tiffany's only selects the diamonds with exceptional cut, they don't use that marketing term for the best cuts, they simiply stop at Excellent as their highest grade. That being said, I put the stats of my 'Excellent' cut Tiffany & Co. diamond into pricescope's cut advisior and got a rating of 0.2. Since the closer to zero the better the cut (and the algorithyms make it impossible to get exactly zero) and considering the crazy shine the diamond gives, I would have to say that the cut is pretty close to perfection.
My guess would be that yes they only sell diamonds with 'Excellent' on their certificates. You can ask to see the certificate on any diamond they show you to verify that.
If youre trying to compare prices between a Tiffany diamond and some other vendor, say BlueNile, I would only look at Signature Ideals in order to compare apples to apples.
This is what I've been told by Tiffany.
I have a Tiffany's 1.45 ct round solitaire and it's not an ideal cut. Mine is rated "very good". I also own an ideal cut Hearts and Arrows stone from White Flash that scores excellent in every catagory. To me both stones sparkle about the same--maybe I have bad eyesight?! I love both my stones equally =)
As to my post above, I now am thinking that the Tiffany diamonds may be in the ideal range but the White Flash Hearts and Arrows stones are in the super ideal catagory.
For the HCA - the closer to 1 the better, not 0.