Pearl

Pearl is the only major gemstone produced by a living organism, forming when a mollusk—chiefly saltwater oysters and freshwater mussels—secretes concentric layers of aragonite and conchiolin, together called nacre, around an intruding irritant. The resulting sphere carries a soft internal glow and a play of iridescence known as orient. Natural pearls, which form without human intervention, have been harvested from the Persian Gulf, Red Sea, and Indian Ocean for more than 4,000 years, making pearl one of the oldest and most universally treasured gems. Cultured pearls, nucleated by deliberate implantation, have been produced commercially since the early twentieth century in Japan, China, French Polynesia, and Australia. With a Mohs hardness of only 2.5 to 4.5, pearl is soft and requires careful handling. It is the traditional birthstone for June.