FROM TOP: Amethyst flower-corsage bib necklace, Melissa Joy Manning ($2,750). Illusions, 78 Main St., Sag Harbor; melissajoymanning.com. Plexiglass and metal necklace, Chanel ($4,600). 15 E. 57th St., NYC; chanel.com. Wailana necklace, Catherine Malandrino ($1,450). 25 Newtown Lane, East Hampton; catherinemalandrino.com
