How does an oyster make a pearl and how long does it take?
Pearls come from a group of water organisms called pearl molluscs, which includes oysters, mussels, and clams from both freshwater and saltwater. The pearl itself actually begins as an irritant. Sand, a pebble, or a pesky parasitic organism gets inside the oyster’s shell. To reduce the irritation, the oyster coats the intruder with layers of a solid, slick material called nacre. The oyster’s mantle tissue secretes the two main components of nacre: thin layers of the mineral aragoniteand a gluelike substance called conchiolin, which cements the layers together. Because the aragonite is translucent, light interacts with the overlapping layers to give the finished pearl its lustrous appearance. Pearl molluscs also coat the inside of their own shells with nacre, so some shells picked up at a seashore are shiny and iridescent inside.
