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 setting. Clockwise from top left: London Collection ring in 18k white gold with diamonds, sapphire and lapis, $6,540; Etincelle de Cartier wedding band in platinum with diamonds and sapphires, $9,500; Bulgari Divas’ Dream Mosaica High Jewelry watch in 18k white gold with diamonds and sapphires, price upon request; Roberto Coin Obelisco bangle in 18k white gold with diamonds and sapphires, $23,500 All available at London Jewelers , 2046 Northern Blvd., Manhasset, LI;  Cartier at Cartier , 2100 Northern Blvd.,…