SAPPHIRE Symbolism: Nobility, truth, sincerity, faithfulness and wisdom Birthstone month: September  Legend: Ancient Greeks and Romans believed that the precious blue stones had the power to protect them from envy and harm. Dazzling detail: A rare variety, the star sapphire displays starlike rays on its surface when cut as a cabochon and viewed under light. Icon: Princess Diana’s Garrard engagement ring, now worn by Kate Middleton, features a 12-carat oval Ceylon sapphire in a diamond halo