If red octagons are suppose to make people stop, what does a blue and white octagon make people do? Gawk! 5 mm in diameter, or 0.70 carat, blue sapphire is featured in the center of the 14 kt white gold octagon. The octagon and bail has 0.13 total carats of round brilliant cut diamonds bead set and with milgrain edging to define its look. Chain not included.