We can divide pearls in different ways, with different definitions. They can be listed as: Freshwater or Saltwater,Natural or Cultured,Whole or Half .
Good saltwater pearls can cost several times more than freshwater pearls of similar quality and size. Not only because an oyster can produce less pearls than a mussel does. It also takes a longer time for an oyster to nurture pearls.
Natural pearls are much more expensive than cultured pearls.
Whole pearls are more valued than blister or mabe pearls.
Most popular pearl types are as bellows: