What is the difference between natural and cultured pearls?

Natural pearls grow in the wild without human intervention. They are very rare, and most natural pearls in the market today are antique. Cultured pearls are grown in pearl farms, and are the direct result of human intervention. The vast majority of pearls in the pearl/jewelry market are cultured pearls. Cultured pearls may be bead nucleated, tissue nucleated or otherwise non-bead cultured, and they are produced in both saltwater and freshwater mollusks.