1. Pearls are formed when a foreign particle such as a grain of sand or a small particle of rock accidentally enters the space between the mantle and shell of an oyster’s body.
2. Oysters cannot reject the particle, and as a defence mechanism its produces a shining coating called nacre on the particle layer by layer.
3. As the shiny layers get added, a pearl is formed.
4. Cultured pearls are artificially formed by inserting a bead in oyster shell and allowed to coat it with nacre over several years.
