The way a pearl is extracted from a shell. Pearl is a hard material produced from the soft tissues of live shellfish.. When a grain of sand or a pest enters the shell of an oyster, then the oyster is disturbed. Unable to expel the 'invader', produces a smooth hard crystalline substance – the pearl – (calcium carbonate) around it to protect himself. As long as the intruder stays there, the shell continues to produce layers of this substance, until after a few years it is trapped inside a smooth and shiny pearl.