Pearl oysters can attach and reattach themselves using the byssus. Sometimes a natural pearl forms when an irritant, such as a fragment of shell becomes lodged inside the mollusk when it is feeding, or a parasite drills through the shell. To protect itself, the mollusk forms a sac around any irritant or invader that managers to get caught up inside its body.
This sac secretes nacre to cover the irritant and, over time, the growing pearls are completely covered with the beautiful iridescent substance we call nacre, or mother-of-pearl. The nacre and sac materials are made by the mollusk's mantle, the layer of tissue cells that surround the body of the mollusk and lines the shell. The mantle tissue cells that make up the pearl sac are called epithelial ep-uh-THEE-lee-yuhl cells. One commonality all cultured pearls share is the nucleus. Every pearl produced commercially today except naturally forming keshi pearls and pearls from Bahrain will have been nucleated.
The nucleus used in all pearls farmed in saltwater today is a mother-of-pearl bead made from freshwater mussel shells found in North America. This bead is made from an oyster shell that has been cut, rounded, and polished. A nucleus is surgically implanted in the oyster's gonads or mantle lobe together with a small section of mantle tissue.
Implanting a bead alone will not stimulate pearl formation. The epithelial cells - mantle tissue- play a vital role in the pearl formation process. As the oyster recognises the nucleus as an irritant, it forms a sac around the irritant before coating it with smooth layers of nacre.
Pearl farms now produce all the cultured pearls used in the jewellery industry today, and, while they are real, genuine pearls formed inside a living oyster, they are produced with a little human intervention.
Saltwater oysters are nucleated by opening the shell a mere 2 to 3 centimetres and making a minute incision in the gonad - the oyster's reproductive organ. The mother of pearl nucleus is inserted into this incision which is then followed with a very small piece of mantle tissue from a donor oyster.
The mantle tissue is placed between the mother of pearl bead and the gonad with the side containing epithelial cells facing the nucleus. These epithelial cells are the catalyst of the pearl-sac. The pearl sac grows around the nucleus and begins to deposit nacre.
This nacre layering is the beauty of the pearl. Saltwater oysters will only produce 1 to 2 pearls per typical nucleation. Akoya oysters can be nucleated with up to 5 beads but the use of only 2 is most common. The Akoya oyster dies at harvest. South Seaoysters Pinctada margaritifera and Pinctada maxima accept only one nucleus at a time but, as they do not die at harvest, they may be nucleated several times.
If a particular oyster has been successfully nucleated several times and consistently produces fine pearls, the oyster is often returned to the wild to strengthen the genes of future generations of spat. An oyster's pearl sac will secrete nacre on nearly any solid object.
This has led to countless attempts to nucleate oysters with material other than oyster shell. Success has been limited, however, and oyster shell is still the main staple of the pearl farmer as it has been since the early s.
The reasons nuclei of non-standard composition has been so quickly rejected in the past is because the density of the nucleus must exactly match, or be extremely close to the density of the host mussel. In order for the pearl to expand and contract in different environments, the nucleus must expand and contract in a compatible fashion. This is known as the thermal coefficient of expansion. The nuclei must also resist cracking, hold a high shine and remain stable over long periods of time.
The material that best fits these criteria is the shell of the Mississippi freshwater mussel from the Unionidae family. In freshwater cultured pearls, cutting the mantle is enough to induce the nacre secretion that produces a pearl -- an irritant doesn't have to be inserted. While cultured and natural pearls are considered to be of equal quality, cultured pearls are generally less expensive because they aren't as rare. Sign up for our Newsletter!
Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Wild Animals. Marine Life. How Do Oysters Make Pearls? Updated: Apr 16, Oysters aren't the only type of mollusk that can produce pearls; clams and mussels can as well.
This irritation causes the oyster to attempt to protect itself, producing nacre to cover the foreign substance. Over time, these layers form a pearl. Do oysters die when you take the pearl? How do you know if there is a pearl in an oyster? Thank you for sharing your comment with us! We hope you will explore other Wonders and learn some cool new facts with us today!
Thanks for spreading the Wonder about pearls, Cherry! We're glad you learned something new with us-- it's like a pearl of wisdom when we Wonder together!
Hi there, Wonder Friend Arleth! We're thrilled to hear that you learned something new today with us! Thanks for sharing your comment, Wondergirl11!
Hooray, we're so happy that you liked today's Wonder, Berkleigh! You're a pearl of a Friend! Hi there, Wonder Friend Camdyn! Hi there, Grace! We have lots of Wonder Friends who take turns responding to Wonder comments! Hi there Wonder Friend SoftballRocks44!
We are undergoing some spring clearing site maintenance and need to temporarily disable the commenting feature. Thanks for your patience. Drag a word to its definition. You have answered 0 of 3 questions correctly and your score is:. Want to add a little wonder to your website? Help spread the wonder of families learning together. We sent you SMS, for complete subscription please reply. Follow Twitter Instagram Facebook. Does every oyster have a pearl? What are cultured pearls? What are baroque pearls?
Tags: See All Tags animals , baroque , clam , cultured , jewelry , mantle , mussel , nacre , natural , Oceans , oyster , pearl. Wonder What's Next? Go ahead and blink! Try It Out Are you ready to learn more about pearls? Be sure to check out the following activities with a friend or family member: Ask an adult friend or family member to take you on a field trip to a local jewelry store. What are you looking for? Pearls, of course! Ask to see a variety of different types of pearls.
What quality are they? How expensive are they? Would you ever wear pearl jewelry? Why or why not? Are pearls always white? You might think so, if you've ever heard your teeth referred to as your "pearly whites. Visit National Geographic online to learn more about Black Pearls. Wouldn't it be nice if things that got under your skin and irritated you turned into pearls? Would you believe they can? Irritations in your life won't turn into actual pearls that you could make a necklace out of.
However, the things that get on our nerves can eventually turn into pearls…of wisdom! When life gets you down and things irritate you, keep your eyes open.
Maybe there's a lesson you're supposed to learn. Cultivate patience and persevere through the rough times. The lessons you learn from such times can often help you deal with — or avoid — similar situations in the future. So when life hands you lemons, make lemonade! If something is irritating you, be patient and see what you can learn from the situation. The pearls of wisdom that form can become jewels of knowledge that help you countless times in the future!
Did you get it? Test your knowledge. What are you wondering? Wonder Words mussel pry precious jewel baroque cultured necklace earring diamond sapphire biological foreign substance irritant mantle nacre wisdom persevere Take the Wonder Word Challenge.
Join the Discussion. Geoff Aug 13, I read every comment and reply on this article and you all have me impressed and proud. It is incredibly refreshing to see such kindness and positivity. I'm really hoping you're all told this often, because what you're doing is something special. I wonder all the time about things but never seek the answers, but you all have inspired me and I am determined to wonder more and learn more wonderful things about the planet we live on.
Thanks again, Geoff. Aug 14, Hello Wonder-Team, This is the first article of yours that I have found and read. I just wanted to google "Is it a clam or an oyster that makes pearls? I work with my hands and she's an educator and she's pretty cool and stuff.
Your last three suggestions to try, specifically the third -- I mean -- I came to figure one thing out on google, but instead, I learned that one thing and also got to read such a wholesome thought.
What kind of Google search was this!? I want more of these! You've got yourselves a bookmark slot ; Also, the article itself was wonderfully written!! Thank you, Geoff. Bensyn Mar 12, The process of making a pearl was more interesting than I thought it would be. You're telling me there are more colors!!!!!!!! Mar 13, We thought that was pretty cool, too. John the doge Jan 16, Robot Jan 14, Jan 16, Wonder Friend Jan 14, Apr 30, This occurs only occasionally, and the reason why is mentioned in this Wonder: "Occasionally, a foreign substance , such as a grain of sand, may find its way into the oyster and get stuck between the mantle and the shell.
Mar 22, Thanks, Sadie! Donna from Alabama Oct 17, When you buy oysters in shells at a department store, do they have pearls in them?
Oct 23, Dab Sep 12, Sep 14, It can be confusing, but not every oyster has a pearl. Jul 25,
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