Eli5: How/ why do oysters make pearls?

Question

Eli5: How/ why do oysters make pearls?

In: 3

Answer 1

I don’t know the nitty gritty of it but if I remember correctly it occurs when they get a foreign contaminate, usually sand, inside their shell. It irrates the internal body of the oyster and to combat this the oyster starts secreting a substance that turns into a pearl which is far less irritating than the gritty sand.