The pearl—the only gem produced by a living animal—has long carried a certain allure. Yet the best mollusk for making this gem—the pearl oyster—doesn't always produce a pearl, and even then, the pearls are rarely perfectly round. It wasn't until the late nineteenth century, when a Japanese scientist discovered a technique to incite oysters to produce these gems, that an industry was formed. Inducing an oyster to create a pearl is only half the battle—the oyster then needs a nutrient-rich, open...