4 Carat Ruby & Diamond Cocktail Ring in Platinum4 Carat Ruby Diamond Cocktail Ring in Platinum. This fabulous cocktail ring features an amazing 4. 45 carat oval shaped ruby that is accented by 2. 56 carats of diamonds. The accent stones in this ring contain eight (8) Round Brilliant Cut and two (2) Trapezoid Cut diamonds to complete a gorgeous dynamic of red and white. The ruby is prong set in platinum, which gives this ring another slight contrasting element of the deep red color. This fine piece