HOW A PEARL IS FORMED

    HOW A PEARL IS FORMED ?

    Pearls are formed inside the shells of some kind of pearl oysters. Something or a grain of sand or a tiny creature gets inside an oyster. 

      If it gets between the mantle and the shell, it irritayes the soft body of the oyster. The oyster cannot throw out the grain of sand or the tiny piece of something. 

       So it starts covering the grain of sand or the tiny piece of something with thin layers of nacre or the mother-of-pearl. Layer upon layer is added and after some years, a pearl is formed.