Crossover appeal. Round-cut diamonds (1/4 ct. t.w.) add an elegant touch to this ring set in sterling silver, making it perfect for any formal affair. Size 7. 1/4 Carat Diamond Ring. Diamond Color Rating Code: I2-I3. Diamond Clarity Rating Code: I. Diamond Cut: Round. Almost all gemstones and blue and black diamonds have been treated to enhance their beauty and require special care. All gemstone carat weights (ct. t.w.), if mentioned, are approximate; variance may be .05 carat. Ring Sizer.