Pearls or Mother-of-Pearl  Pearls are formed inside the shell of certain mollusks. In response to an irritant inside its shell, the mollusk deposits layers of nacre around the irritant and it grows into a pearl.  Pearls are usually white, sometimes with a creamy or pinkish tinge, but may be tinted many other colors. Both mother-of-pearl and pearls are made of "nacre".  Mother of pearl is a coating of nacre on the inside of the shell itself and typically includes part of the shell.

Natural Pearls or Cultured Pearls  Natural pearls occur on their own while cultured pearls are cultivated by the insertion of a small bead or mantle tissue around which the pearl is formed.

Freshwater Pearls or Saltwater Pearls  Freshwater pearls are formed in fresh water mussels. Saltwater pearls grow in oysters that live in the ocean, usually in protected lagoons.

Mabe Pearls or Blister Pearls  Both pearls grow on the inside wall of the shell. Mabe pearls are grown by adhering a small dome onto the inside surface of a mollusk's shell. Once it has been coated with nacre it is cut away, filled with resin and backed with mother of pearl. All blister pearl are formed by adhering and object to the shell but only the dome shaped blister pearls are Mabe pearls.

Osmena Pearls or Turbo Shell Pearls  These are often mislabeled, so  we consulted an expert: Turbo pearls are cut from the side of a turban shell and naturally white, but sometimes tinted. True Osmena pearls come from the nautilus shell, actually the inner spiral of the shell. Osmena pearls are naturally silver blue, but sometimes dyed various colors or bleached white. It becomes difficult to tell which is which. The term Osmena is more widely known and Turbo pearls are often called Osmena, because they are both domed flat backed cabochons. Both pearls are technically mother of pearl.