Tiffany Co. Aquamarine Diamond Ring in Platinum.  This Tiffany and Co. cocktail ring features a 37.60 carat emerald cut aquamarine with .91 carats of diamond accents and is set in platinum. The massive aqua is sure to turn heads, yet the clean platinum setting with the elegant baguette accents make it more approachable despite the size. This is a fabulous ring that would make a prized piece in just about any collection.