When akoya pearl sales shot up 40 percent in 2015—and then another 10 percent this year—Daven Sethi, vice president of New York City–based Tara Pearls, knew the classic white pearl was on the brink of a new crest of popularity. “The majors have been doing superb with akoya,” Sethi says. White akoyas have been a jewelry-box staple ever since the Japanese inventor and cultured-pearl pioneer Kokichi Mikimoto perfected the culturing process around the turn of the 20th century. World War II veterans returning home to America began snapping up akoyas for their sweethearts, while celebrities and fashion darlings such as Jacqueline Kennedy and Coco Chanel also helped catapult the pearls to must-have status.  But over the years, new and top-quality varieties of Chinese freshwater cultured pearls began to draw the attention of designers. The classic akoyas—literally your grandmother