The pearls used as jewelry - the precious pearls - are largely farmed for the purpose. They are known as cultured pears as opposed to pearls found naturally in oysters and related bivalves. Certain species of oysters are implanted with a small grain of sand called the 'seed;. This irritates the oyster and the pearl slowly forms around the irritant. It's a process akin to building up a callous on your foot if your shoes don't fit. Does the oyster feel pain in the process? No one is really sure. It may not be the same kind of pain humans feel, but there is a physical reaction to an artificial irritant. Harvesting the cultured pearls kills the oyster. Whether painful or not, the animal is intentionally used for the purpose. Definitely against Vegan philosophy.