How does an oyster produce a pearl and what is a pearl made of?
All shell-bearing molluscs (snails, clams, oysters) can produce pearls, but the pearls made by oysters and freshwater mussels are really the only ones of commercial value. Mollusc shells are made by a sheet of tissue called the mantle. The mantle surrounds the animal and is attached to the shell by muscles. There is only a tiny space between the mantle and the shell, and sometimes an unwanted object such as a sand grain or parasite gets stuck in this space. This small object can be very irritating, and so the oyster uses its mantle to surround the sand grain with layers of nacreous shell. This shell material (also known as mother-of-pearl) is very shiny and beautiful, and also lines the inside of the oyster’s shell. The oyster keeps putting layer after layer of shell over the tiny piece of sand, eventually forming a pearl. The formation of pearls is quite random, and so “pearl farmers” have taken the matter into their own hands. They intentionally seed oysters with small pieces of shel
