[header] How to buy pearls [title] Choose a growth style. [step] Cultured pearls grow through a process in which a small piece of sediment-a grain of sand or a bit of shell-is deposited inside of an oyster. The oyster then coats the deposit with a glossy secretion called nacre. 
Over time, the nacre builds layers to form a pearl. Originally, pearls could be found in abundance in oysters throughout the oceans, but now they can be grown in laboratories.