Champagne Diamond Engagement Ring in PlatinumChampagne Diamond Engagement Ring in Platinum. This lovely Retro engagement ring features a 1. 22 carat Old European cut champagne diamond set in platinum. Surrounding the center diamond in a twisting fashion that resembles a loose knot being tied, are round brilliant cut diamonds. The accent diamonds along with the platinum add a soft contrast to the champagne diamond. This is a subtle beauty with interesting qualities that reveal themselves upon