Pearls have fascinated civilizations for thousands of years. Although it is unknown when pearls were first discovered, civilizations in China, India, and the Middle East are among the first civilizations known to have cherished these rare treasures. Over time, pearls have continued to grow in popularity, and today, they are one of the most popular gemstones.
Regardless of whether a pearl is natural or cultured, both types of pearls are formed through a similar process. Pearls are formed inside the shell of certain mollusks as a defense mechanism against a potentially threatening irritant such as a parasite inside its shell, or an attack from outside, injuring the mantle tissue. The mollusk creates a pearl sac to seal off the irritation.
NATURAL PEARLS VERSUS CULTURED PEARLS
The difference between natural and cultured pearls focuses on whether the pearl was created spontaneously by nature – without human intervention – or with human aid. For thousands of years, natural pearls were the only pearls available to the numerous civilizations that treasured them. Nevertheless, natural pearls are incredibly rare, which has partially led to their value. In recent years, however, modern technology has allowed us to make cultured pearls.
Natural pearls are formed inside of oysters, under a set of accidental conditions when a microscopic intruder or parasite enters the inside of the oyster shell. The oyster, being irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes natural chemicals to cover the irritant. This chemical secretion process is repeated many times, thus producing a pearl. Because this entire chemical process is entirely natural, it is rather rare for an oyster to create a perfectly round pearl. In fact, most of the natural pearls created come in many shapes other than round.
Cultured pearls are created by transplanting a mother of pearl bead into a recipient oyster shell. Thinking that an intruder has invaded its shell, the oyster will respond by secreting its natural chemicals to cover the “intruder.” Unlike natural pearls, the “intruder” in cultured pearls is always spherical. Accordingly, the chemicals that the oyster secretes will simply cover the sphere, which always results in spherical cultured pearls.
Cultured pearls can be distinguished from natural pearls by X-ray examination. Nucleated cultured pearls are often ‘pre-formed’ as they tend to follow the shape of the implanted shell bead nucleus. Once the pre-formed beads are inserted into the oyster, it secretes a few layers of nacre around the outside surface of the implant before it is removed after six months or more. When a cultured pearl with bead is X-rayed, it reveals a different structure to that of a natural pearl. A cultured pearl shows a solid center with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings.