The intense oceanic hues of the blue Australian opals used in this statement-making Lydia Courteille necklace informed its maritime design. The gems even started out in the sea—as knots of plankton that over time filled in with the opal mineral. The opals “are a beautiful blue,” says the Parisian designer. “When you look at them, you think immediately of the deep sea.” Courteille, a veteran antiques dealer, adds that the critter-filled design was also inspired by “René Lalique and the Art Nouveau…also Jean Schlumberger.” She created the sapphire-and-amethyst necklace—a new addition to her ever-growing bestiary—for a lover of bold jewelry, to be sure. But also “to wake up the siren who sleeps inside every woman.” Consider ours roused. Seahorsing Around The 18k gold necklace includes two blue Australian opals (102 cts. t.w.); 1.58 cts. t.w. white diamonds; 1.