What part does the mantle play in a mollusk?

The mantle is a crucial part of a mollusk as it is responsible for secreting nacre, also known as mother-of-pearl. This secretion forms the inner layers of the shell and is the substance from which pearls are made. The mantle lines the body cavity and plays a significant role in the mollusk's ability to create its shell, particularly in species like oysters, which can produce pearls as a defense mechanism against irritants. The process involves the mantle cells secreting layers of nacre around an irritant, which over time becomes a pearl. This characteristic of the mantle not only contributes to shell formation but is also central to the value and allure of pearls in the jewelry industry.