A real pearl is the result of an accident. A grain of sand or some other item accidentally gets into an oyster. Then the oyster tries to protect
itself by covering this sand with a coating of pearl. This material is called "nacre" and comes from glands within the oyster.
This paragraph is mostly about
O 1. how pearls are formed.
2. why sand gets into oysters.
3. how oyster glands work
4. why pearls are expensive.