Nearly everybody knows that pearls are formed by oysters, but not many people know the true process. Before we get into the discussion of how oysters make pearls, we’d like to give you a brief lesson on their anatomy. As mentioned in previous entries, oysters, much like mussels, oysters, and clams, are bivalves. This means that they have a split shell and the two halves of it are held together by a powerful set of abductor muscles. Like their brethren, oysters feed through straining and their diet mostly consists of plankton and krill. The shell of an oyster continues to grow as the oyster does and it is produced by an organ know as the mantle.2. The mantle protects the delicate inner parts of an oyster and keeps it safe from predators.
Contrary to popular belief, oysters are not the only shellfish capable of producing pearls. Clams, mussels, and scallops can also produce pearls, but they do so far less frequently and with less attractive results. While we sell the best fresh Blue Point Oysters, Malpeque Oysters, and PEI Oysters in CT, these are not the kind of oysters that produce pearls. That’s okay with us though, because we’re seafood enthusiasts, not jewelers.
The oysters that do produce pearls are great in number, but are rarely eaten within the United States.1 They can be found in both freshwater and saltwater and all belong to the Petriidae family. Some of the more prominent varieties include Gulf Pearl Oyster, White-Lip and Black-Lip Oysters, Shark Bay Pearl Oysters, and the Akoya Pearl Oyster.3 While pearls are usually thought of as being white, they can actually come in several different colors. In addition to white pearls, there are also gray, red, green, blue, and black oyster pearls. The black pearls are among the most rare and are found exclusively in the South Pacific.2 No matter the color, oyster pearls fall into two varieties – natural and cultivated.
When an oyster forms a natural pearl, the process is initially triggered by some sort of unwelcome element getting inside of their shell and irritating the mantle. When this happens, the mantle secretes a substance called nacre (also known as “Mother of Pearl”3), which is composed of the nutrients in the oyster’s diet. When released, this substance coats the inner portion of an oyster’s shell. Over time, more and more nacre is released until the offending party is encapsulated and this is how the pearl is formed. Finding a pearl in a wild oyster is much less common than one might think. In fact, typically less than 1% of all oysters living in the wild will contain a pearl at any given time and of this 1%, not all hold the traditional spherical shape. Some oysters will produce more formless and aesthetically unpleasing pearls that won’t likely find their way into a necklace any time soon. Due to their rarity, naturally formed pearls are much more valuable monetarily than cultivated pearls, even though it is very difficult to tell them apart once they’ve been extracted and cleaned.
The process by which cultivated pearls are formed is quite similar to the way natural pearls are formed, except for the fact that these pearls are formed by oysters living on farms or captures by local shellfish hunters. The people in charge of these oysters speed up the process a bit by cutting a small slit in the oyster’s mantle and inserting an irritating substance. Once this is done, nature takes its course and soon a cultivated pearl is formed. While these pearls aren’t quite as valuable as their naturally formed relatives, they are much more plentiful as over-aggressive pearl hunting has made wild pearl-producing oysters somewhat scarce, with their average lifespan being only around 9 years due to this problem. (An oyster can naturally live up to well past 20 years if not interfered with.)
The next time you see someone wearing a pearl necklace or are asked by an overly curious child as to how pearls are formed, remember this article and impress everyone with your “pearls” of wisdom.
1. Author Unknown
How Do Oysters Make Pearls?
3. Author Unknown
Nacre- What Pearls are Made of