Among all of the gemstones available in this world, the pearl is absolutely unique. This is due to the fact that it is the only one which is formed entirely within a living being.
Pearls are produced in two basic ways: the Natural way – without human intervention – and the cultured way – when they are farmed by people.
Natural pearls occur when some form of irritant – be it a piece of shell, bone, scale, or even a parasite – lodges itself into a pearl producing mollusk such as an oyster, mussel, or abalone. To protect itself from the foreign body, the mollusk forms a nucleus over the foreign element, and continues to coat it with layers of nacre over the next several years. The factors that determine the size, color and shape of the pearl have to do with the size and shape of the nucleus, and the region of the ocean in which the mollusk resides.
Today, almost any pearl that you’d encounter is a cultured pearl. Desirable natural pearls are extremely rare, and hence are quite prohibitively expensive. In fact, only one in approximately 10,000 oysters not in farms will ever produce a pearl, and of those, only a very small percentage would ever yield a gem that is the right shape, size and color of something desirable.
Furthermore, the majority of natural beds of pearl-producing mollusks have been depleted due to over-harvesting in the past. This is the reason that such efforts were made to grow pearls artificially, which the Japanese accomplished in the early 1900s, by planting a nucleus into the pearl-bearing mollusk, and then returning it to the ocean.
The primary difference that exists between cultured and natural pearls is in the thickness of the nacre – the outer shell that holds the color and luster of the pearl. In order to make pearls more quickly, cultured pearls are usually implanted with larger nucleus than those which would begin a natural pearl. Even with the larger nucleus, it still takes two to three years to grow a fine pearl, so it’s easy to understand why time reduction is important to pearl farmers.
Natural pearls have always been deemed rare, and are universally costly. They are most commonly sold by their carat weight, however, most of the natural pearls on the market today are vintage pearls, as virtually every pearl producer now relies on cultured pearls. Natural pearls are simply too risky, rare, and expensive to find and sell.
It is recommended that if you do have the opportunity to buy a natural pearl, you should refrain from buying it unless it comes with an official gemological x-ray certificate, which proves that it is natural, and states its pearl quality. For something so rare, expensive, and beautiful, a little security is a must.