What Is an Oyster? How Does It Make Pearls?

Cultured pearl grafting.

Pearls are precious gems that come from the sea. They are the babies of the almighty oysters, natural miracles created by Mother Nature herself. But, what exactly is an oyster? And, how do these living creatures make pearls?

Photo : Fred Ward/Black Star
A 14-mm cultured black pearl emerges from the gonad of this P. margaritifera grown in the Marutea lagoon. Note the mantle surrounding the pearl, and the characteristic black color on the inside edges of the shell. Image Source

What Are Oysters?

Oysters are sea animals or mollusks with close relations to:

  • Mussels
  • Clams
  • Scallops

The Jobs of the Oyster’s Shell

Located at the joint where the parts of two valves meet each other. These valves are usually kept open, so the oysters can eat, which every oyster must do regularly to thrive.

Because they are mollusks, their way of eating is by drinking water and using gills to filter nutrients from it. Those nutrients then travel to the oyster’s stomach for digesting, and excess water is spit out through the shell.

The Parts of an Oyster Shell
The Parts of an Oyster Shell. Image Source: Info Visual

8 Main Body Parts of an Oyster

What is an oyster? Let’s go over a pearl oyster’s basic anatomy to help you get a better understanding. Inside the shell of an oyster, you’ll find eight primary body parts:

  1. Mouth
  2. Heart
  3. Stomach
  4. Intestines
  5. Mantle
  6. Anus
  7. Abductor Muscle
  8. Gills
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The pearl’s mantle is responsible for producing the nacre with actually forms the gem inside the oyster (see How Do Oysters Make Pearls section below).

Oysters & Pearl Reproduction

Oysters have a very interesting reproduction system mostly because some types have multiple sex organs. According to experts, some have both female and male organs, while others just have one or the other. Those with female sex organs release millions of eggs into their waters. For both sexes, pearls are reproduced inside the oysters.

How Are Natural Pearls Born?

The life of a natural pearl, one born in the ocean seas, begins when an intruder invades the oyster’s shell. In many cases, this is simply a grain of salt. However, it can also be food floating in the way or some other contaminant. Once it slips inside the mollusk’s shell, it feels the need to protect itself from the irritant.

Bahrain pearl divers shave their heads, grease their bodies and use ropes and baskets to dive for natural pearls.
Bahrain pearl divers shave their heads, grease their bodies and use ropes and baskets to dive for natural pearls. Krikor calls them “The Japanese who killed the Natural Pearl.” Image Source: Selamta Magazine

That’s when the oyster goes into defense mode. It begins to cover the object with layers of secretion known as nacre. Multiple layers of nacre are formed, referred to as Mother of Pearl, to continue coating the irritant. In time, a natural pearl is born.

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Pearl divers must go deep into the ocean’s waters to retrieve oysters, hoping they all contain pearls. Not only is this dangerous, but it is the main reason most experts believe very few natural pearls still exist in the sea. That’s why the culturing process is so important to make pearls to meet market demands.

How Are Cultured Pearls Born?

Cultured pearls are created the same way as natural pearls. However, there are two distinct differences between natural pearls and cultured pearls:

  • Cultured pearls are nurtured by pearl farmers on pearl farms instead of in the ocean
  • The irritants used to activate the nacre in cultured oysters are manually inserted by the pearl farmers

Pearl oyster divers have depleted the seas of the precious gems. These days, it’s almost impossible to find the gemstones in the ocean’s blue. Cultured pearl farms make it possible to “create” the gems with having to dive for oysters.

Cultured pearl grafting.
Cultured pearl grafting. Image Source: Krishi Jagran

The pearl farmers insert an irritant inside the oyster manually, usually a shell bead nucleus. From there, they feed, care for and nurture the mollusks, keeping them safe from environmental conditions as well as predators. If not, they will not be able to successfully make pearls that are valuable to the market. 

READ MORE:  Understanding Pearl Colors: How Do Oysters Create Different Color Gems?

After the irritant is inserted, the oysters kick into defense mechanism mode, creating layer upon layer of nacre, just like with the natural pearl process. Therefore, not only are cultured pearls actually real pearls, they are more abundant, making them more affordable than natural pearls.

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Kiesha Joseph
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Kiesha Joseph

The Pearl Source Content Manager at Content Marketing Geek Corporation
Kiesha Joseph is the Managing Content Editor for ThePearlSource.com, a leading online pearl jewelry website offering high-quality pearls at affordable prices. Kiesha is a Content Marketing Geek who enjoys educating her audience on a broad range of topics, including trends in marketing, SEO, jewelry, fashion, celebrity style and more.
Kiesha Joseph
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