A pearl is an organic gemstone made from the calcreous concretions of mollusks. Pearls can be either saltwater pearls, which include the akoya, Tahitian and South Sea varieties or Freshwater pearls cultured in either China or the United States. The vast majority of pearls available on the jewelry market today are cultured pearls, meaning that human intervention forced the mollusk to begin laying down nacre over a bead nucleus or other irritant.
Wild pearls, or natural pearls, are gems that have occurred without human assistance, usually due to a parasite or other irritant working its way inside the mollusk which then begins to lay nacre over it in concentric layers to smooth the irritant over.
See also: Nacre, Calcium Carbonate, Akoya Pearls, Tahitian Pearls, South Sea Pearls