Natural pearls occurred when irritants such as parasites damaged the outer shell of an oyster and entered into the soft tissue. As a natural defense mechanism, the oyster produced a coating on the irritant. This coating is the nacre and it’s built up of many thin layers, resulting in a pearl.
It’s a myth that the entrance of a sand particle can produce nacre. Nacres only form on living organisms. Pearls are a result of a natural living organism, unlike gems which are a result of minerals present in the earth.
Our fascination and constant search for pearls has made natural pearls extinct. Today’s pearls are cultured pearls. That is they are made the same way that natural pearls were made, but with human intervention.
Baby oysters are grown at pearls farms. After they have grown stronger and larger, about 3 years, they are removed from the water and taken to lab. They are placed in warm water to relax the oyster. Then the oyster is opened and a bead is inserted. This is how the bead is inserted; a cut is made in the oyster’s body, nucleus from the shell of a donor mussel along with a small amount of tissue from the donor oyster and a little water is inserted. This stimulates the production of nacre by the oyster. Then the implanted oysters are returned to the salt water pearl farm. Over the years, pearl exterior starts forming. First a porous layer forms, then the nacre starts forming. The nacre is made of micro-layers which are a form of calcium carbonate. These layers are made of microscopic plates. That’s why when a cultured pearl is rubbed against teeth, it feels rough.
It takes about 1 to 3 years to harvest the oysters. They are usually harvested during winter, since the cold water slows down nacre production. Once the pearl is taken out, the productive oysters can re-planted to produce larger pearls as the oyster grows throughout the years. The longer the harvesting time, the thicker the nacre. Thicker nacre is a more valuable and desirable pearl. Pearls with thin nacres, can be damaged (loose their luster) easily with perfume, lotion and body fluids.