Invertebrate Paleontology

What is the difference between a natural pearl and a cultured pearl?
Answered by Discovery Channel
  • Discovery Channel

    Discovery Channel

  1. Oysters form pearls to protect themselves when foreign substances invade their shells. The oyster isn’t so concerned about the shape of the pearls it makes - just about whether they stop those foreign objects from causing harm. Oysters have an organ called a mantle; it’s responsible for increasing shell size as the oyster grows. The mantle produces a substance called nacre, which lines the inside of the oyster’s shell. When a foreign substance sneaks into an oyster between its mantle and shell, the mantle makes layers of nacre to coat the substance. These layers become a pearl.

    That means that natural pearls can be less than perfectly round; such pearls are called baroque pearls. To ensure that an oyster makes perfectly round and perfectly desirable pearls, pearl harvesters often give the mollusks a hand. To do so, the harvester makes a small cut in the oyster’s mantle tissue and puts tiny irritants into the cut. In freshwater oysters, just the cut is enough to induce the oyster to start its pearl-making process. These human-assisted pearls are called cultured pearls.

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