Of them all, one of the most simple and yet complex is the oyster, the mother of the pearl. From time to time, an alien body (a grain of sand, for example) may enter the oyster, which the animal then tries to expel. If it fails, the mollusk takes defensive action against the irritant and deposits around the intruder, in concentric layers, an iridescent substance known as nacre. In time, and with great luck, a natural pearl begins to form.

In the process of cultivating pearls, men attempt to reduce elements of chance by skillfully inserting foreign matter into a healthy, mature oyster or mussel and then carefully nurturing the mollusk over periods of up to three years. It is far from the easy process it may, at first, appear to be.

For all its apparent simplicity, an oyster or mussel is an extremely delicate creature. However skilled the operation and cultivation procedures, a large percentage of these animals will eventually reject their implants. Of every 100 harvested pearls, only one or two will be perfect. A sizable percentage of every crop will be totally unusable and must be discarded. For these reasons, any pearl (cultured or natural) is considered one of Nature's great miracles.

Today, there are three main groupings of cultured pearls: Akoya, South Sea, and Freshwater.