Natural pearls are precious gemstones formed inside the shells of certain mollusks, such as oysters and mussels. They develop when an irritant, like a grain of sand, enters the shell. The mollusk secretes layers of nacre, a substance that coats the irritant, eventually creating a lustrous pearl. Unlike cultured pearls, which are produced through human intervention, natural pearls occur without any assistance. They are rare and highly valued, often sought after for their unique shapes and colors. The process of forming a natural pearl can take several years, making them a symbol of beauty and rarity in the world of jewelry.