Why Do Oysters Make Pearls?

Oyster is a common name for several different bivalve mollusks that are found in water; therefore, it is true that not all oysters can make pearls. The ability to make pearls depends on whether the oyster has an organ called a mantle. This organ produces a material called nacre, or mother pearl, which forms the layers on the pearls.

Why do oysters make pearls? Oysters make pearls as a defense mechanism, like when an irritant, grain of sand, or food finds its way into its mantle. The mantle is a thin tissue layer separating the shell from the soft body. It produces a material called nacre in the irritant’s presence leading to the formation of a pearl.

This article expands on the topic in great detail and includes an explanation of the formation of pearls and the different types of pearls. We also discuss how all oysters make pearls and if any pain is caused to them in the pearl-making process.

Why Do Oysters Have Pearls in Them?

Oysters have pearls in them mainly because some intruders, such as parasites or particles, somehow managed to get into their mantle. This causes their fragile bodies significant discomfort and irritation. An oyster’s response to this is to begin covering the foreign intruder or particle with layer after layer of nacre.

Nacre is a combination of calcium carbonate and protein, which is flexible and goniochromism. Thus, it can change color when you change the angle you are viewing in, produced by the inner shell layer called the mantle. This process results in the formation of a pearl hence the reason why oysters have pearls in them.

Do All Oysters Make Pearls?

According to a study written by Paul Southgate and Hector Acosta from the University of the Sunshine Coast, only oysters with a mantle can have pearls in them. As mentioned earlier, pearls are made due to the presence of nacre, which is secreted by the mantle. 

Some oysters may also be initiated to form pearls. This is possible when pearl farmers deliberately insert irritants into the oysters and return them to their habitat. The oysters will react to the inserted irritants the same way they would to natural irritants and begin forming layers that constitute pearls.

It is important to note that pearls formed through the artificial addition of irritants are different in some ways. Pearl experts have ways to figure this out. For example, natural pearls have layers similar to onion when looked up through a microscope, while the pearls formed by manually introducing an intruder have orange-like layers.

Do Oysters Die When You Take the Pearl?

Taking pearls from oysters is an activity practiced by pearl farmers unless, of course, you get lucky and interact with a pearl when having an oyster as a meal or when fishing in the deep sea. Harvesting pearls does not kill the oyster because pearl farmers are experienced and extra careful when extracting pearls. 

When pearls are readily formed, they can be extracted depending on the farmers’ schedules, but this only applies to cultured pearls because naturally formed pearls cannot be scheduled.

The extraction process begins with the oysters being removed from their habitat, either salty or freshwater. They are then transported to the harvesting facilities, where they are opened, and the pearls are extracted from their bodies.

Do Oysters Feel Pain When Making Pearls?

Helen Scales, a marine biologist, answers the question if oysters experience pain when making pearls, saying, “Oysters might probably not feel any pain, but we do not know.” She goes ahead to confirm that oysters have a nervous system; hence, they can respond to environmental changes and destruction as quickly as they sense them.

They also do not have a central brain, like us humans, but masses of nerves around their bodies instead. We can conclude that pearl making for oysters is a condition by their nervous system to protect itself from irritation. So, their chances of feeling pain during the pearl-making process are minimal.

How Long Does It Take for an Oyster to Make a Pearl?

Research and a long study into pearls and oysters have shown that the longer the time oysters take to make pearls, the larger, higher quality, and more valuable the pearls will be. Different types of pearls have different periods for their formations. The following are the two major types of pearls and their periods of formation.

Natural Pearls

These are the mother of all pearls because pearls were discovered through them. These pearls are timeless since they occur naturally and at an oysters’ pace. As for where they were discovered, that remains a mystery. As time goes by, these natural pearls continue being rarer, almost extinct.

Cultured Pearls

Unlike natural pearls, cultured pearls have human supervision from the beginning of their formation to when the final product is ready. Therefore, they have a period when they are monitored, and when the time comes, they are extracted from the host, which is the oyster.

Cultured pearls are divided into four major types of pearls:

  • South Sea Cultured Pearls. These types of pearls are well known for their large nature. Their diameter is approximately1.5cm (0.59″). This is because they take the longest time, mostly 2 to 3 years, to form. They can be white, silver, or golden; it all depends on the oyster forming it. Philippines, Australia, and Indonesia are the leading sources of the south sea cultured pearls.
  • Tahitian Cultured Pearls. This variety of pearls come in the widest range of colors, including green, purple, blue, or even a pink overtone. They take around 18 to 24 months to reach a diameter of 1cm (0.39″). They are mainly extracted from the salty waters of the islands of French Polynesia.
  • Akoya Cultured Pearls. This is the most common type of salty watered cultured pearl in the western market. It takes 10 to 14 months to reach a diameter of 0.9cm (0.35″). The most renowned colors are white and cream. Most pearl dealers consider these pearls posh and elegant.
  • Freshwater Cultured Pearls. This type of pearls, as the name suggests, is extracted from freshwater oysters, unlike the other three types. Thus, they can be found in freshwater lakes and ponds. China is the leading supplier of these pearls, which come in various sizes and colors and are relatively fairly priced.

How Rare Is It to Find a Pearl in an Oyster?

Natural pearls are rare since they occur naturally; hence no human knows when they have begun forming and when it is done. Many centuries before cultured pearls were discovered, hundreds of oysters used to be caught and opened up randomly. This used to lead to the death of most of them, and for what? Only to find one pearl or none at all.

But as time went by, people discovered other ways to obtain these pearls without recklessly killing these creatures. Thus pearl farming came by. This economic activity helps such that pearls are readily available since humans monitor them. Do not get me wrong; natural pearls are also in the market. It’s just that they are very rare to find.


Oysters have proven to be very valuable over the years, and many different designers have embraced pearls into their designs. This means that the demand is getting higher. And to keep up with the demand, you and I have the responsibility to keep the environment clean, especially the sea, which is the oyster’s natural habitat.


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