Platinum Blue Sapphire & Diamond Ring. The ring features one step-cut natural blue sapphire, weighing 1.87 carats, set within four prongs. The sapphire is set in the center of a radiant shaped halo of natural round brilliant cut diamonds. The sides of the ring are trimmed with diamonds. The ring is edged with a milgrain finish. The diamonds weigh 0.50 carats, F-G in color and VS in clarity.