The Graff Asscher Cut
The stone is 'Asscher cut', which is a modern emerald cut that leans towards square rather than rectangular. It weighs 21.46 carats, is a D in color grade (completely colorless) and FL in clarity (flawless). This might not be a REALLY famous diamond right now, but it might be some day - it certainly has the potential. The ring has appeared in a series of ads in the New York Times, along with a 25.74-carat D-Flawless oval shaped diamond, and a large heart cut diamond, both in rings.