Natural Pearls
In the past, natural pearls were collected by pearl divers primarily in areas around the Persian Gulf and the Red Sea. Pearl divers would travel on a pearling vessel for weeks at a time, collecting shells from pearl beds. The shells were opened on board and the proceeds of the discovered pearls were split between the crew - not evenly, however.
Today, natural pearls are primarily found as a byproduct of the fishing industry and to a smaller extent, local, intentional collection - especially in Central America.
Cultured Pearls
There are two varieties of cultured pearls; saltwater and freshwater. Their harvesting methods vary slightly.
1. Saltwater
Saltwater pearls are bead-nucleated pearls grown in the reproductive organ of saltwater mollusks. This is an organ in the body of the mollusk known as the gonad. When a pearl is harvested, the shell is opened slightly, an incision is made to the gonad and the pearl removed. In the case of Tahitian and South Sea pearl culture, a new nucleus is often inserted and another pearl is grown. In the case of akoya pearl production the mollusk is not renucleated.
2. Freshwater
Freshwater pearls are tissue-nucleated pearls grown in the mantle tissue organ of freshwater mussels. This is the large muscle that attaches to either side of the mussel's shell. Because this muscle is large, it may accept many implants, up to 16 on either side of the valve.
When freshwater pearls are harvested, small incisions are made on the mantle and the pearls removed. Often the mussel is returned to the water to grow a second, bead-less regenerated pearl, or a CBSB beaded freshwater pearl.