Pearls are classified by their origins and their shapes.
Pearl Origin Classifications
Natural pearls are formed when an accidental intruder enters a mollusk's shell and continuous layers of nacre grow like onion skins around the particle. Natural pearls vary in shape depending on the shape of the piece being coated.
Natural pearls have always been considered rare and are quite expensive. They are usually sold by carat weight. Most natural pearls on today's market are vintage pearls.
Like natural pearls, cultured pearls grow inside of a mollusk, but with human intervention. A shell is carefully opened and an object is inserted. Shapes of objects vary, depending on the final shape of pearl that's desired.
Over time the object becomes coated with layers of nacre. The depth of the nacre coating depends on the type of mollusk involved, the water it lives in, and how long the intruder is left in place before being harvested. As nacre thickness increases, so does the quality and durability of the cultured pearl.
Cultured pearls are sold by their size in millimeters.
Saltwater pearls originate within a saltwater mollusk. Saltwater pearls can be either natural or cultured.
Freshwater pearls grow inside of a freshwater mollusk one that lives in a river or a lake.
Pearl Shape ClassificationsSpherical pearls are round, which is traditionally the most desirable shape. The rounder the pearl, the more expensive its price tag.
Symmetrical pearls include pear shaped pearls and other shapes that have symmetry from one side to another, but are not round.
Baroque pearls are irregularly shaped pearls. They are often the least expensive category of pearls, but are unique and quite beautiful.