How is a pearl made?

Answer 1

Answer Natural Pearls

Most importantly, a pearl is not formed from a grain of sand.

A natural pearl forms when something organic, most often a parasite, penetrates the shell of a mollusk and lodges within the soft inner body of the animal. Upon penetrating the shell the parasite encounters cells within the mollusk's mantle tissue known as epithelial cells. These cells grow into a sac which envelopes the intruder. This sac is known as a pearl sac. Once the sac has developed the cells begin excreting a chemical substance of aragonite and calcite. This is known as nacre. A natural pearl is composed of nacre. Cultured Pearls, Saltwater and Freshwater

Saltwater pearls are cultured by inserting a bead made of freshwater mussel shell into the gonad of a host mollusk. Along with this bead, a small piece of donor-mollusk mantle tissue is inserted. This tissue contains the epithelial cells needed to grow the pearl sac and initiate nacre deposition. The most common varieties of cultured saltwater pearls are akoya, Tahitian and South Sea. Freshwater pearls are cultured by inserting a small piece of mantle tissue into an incision made in the mantle of a host mussel. A bead is not needed and is rarely used except in beaded cultured freshwater pearl production (CBSB fireball pearls). Because the graft is made in the mantle tissue of the freshwater mussel instead of the gonad, a freshwater mussel may be grafted multiple times. Most often 12 to 16 grafts are inserted on either side of the valve, producing 24 to 32 pearls.