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The Real Story Behind Bead Making | Smithsonian Voices | National Museum of Natural History

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The real story behind pearl making

Smooth beads in the shape of orbs and ovals are typically created by bivalves, such as mussels, on pearl farms. As with all gemstones, the fewer flaws they have, the more valuable they are. (Chip Clark, Smithsonian)

Most gemstones come from the bowels of the Earth, made by pressure and heat over millions of years. But pearls – the most famous biological gems – come from the bowels of mollusks.

“Pearl is a word we use for a brilliant creation that a mollusk produces. If debris gets stuck in a mollusk and they cannot remove it, they coat that debris with their own mother-of-pearl or shell material, ”said Gabriela Farfan, environmental mineralogist and Coralyn W. Whitney stone curator. precious stones and minerals at the Smithsonian’s National Museum of Natural History.

While all mollusks, including oysters, mussels, and clams can technically make pearls, only certain saltwater clams and freshwater mussels are used to commercially cultivate gem-grade cultured pearls.

“Only certain groups of molluscs use a substance, called nacre, which gives gem-quality pearls their opalescent luster,” said Chris Meyer, marine invertebrate zoologist and mollusc curator at the museum.

By collecting and analyzing the pearly pearls, scientists can learn more about how mollusks create these brilliant gems, and how this biological process might change as the Earth’s waters warm.

Gems made by mollusks

Pearl inside a vertical half-shell of a bivalve

Unlike most farmed pearls, natural pearls often stick to their parent’s shell as “honeycomb pearls.” They are also less smooth but due to their rarity they are no less valuable than their cultivated counterparts. (Chip Clark, Smithsonian)

Molluscs make pearls as protection against irritants that slip into their soft tissues. They do this by exuding layer upon layer of shell material. For some animals, this material is mother-of-pearl, or mother-of-pearl.

“All the animal does is put a scab around an intruder, like a grain of sand or a parasite,” Meyer said.

Mother of pearl is a type of crust that gives pearls their pearly luster. But it’s also special for another reason. The material’s recipe, made from organic secretions with a carbon-based mineral known as aragonite, makes it exceptionally strong.

“These are mineral and organic parts that go together like bricks and mortar,” Farfan said.

This brick-and-mortar process dates back at least 200 million years in the fossil record, but natural pearls are incredibly rare. So, people are now cultivating pearls to do more for the gemstone market.

“There’s this industry that knows how to handle the production of pearls, which has led to all of these pearl farms,” Meyer said.

Sowing an industry

Black pearl on white fold

Cultured pearls and natural pearls can be of different colors, depending on the mother of pearl color of their parents. (Chip Clark, Smithsonian)

Farmed or cultured pearls are generally smooth and spherical, due to the way they are made.

“Basically, the pearl farmers very carefully insert a little shell bead into the shellfish. Then they gently put the mollusk back into the ocean or lake and let it grow a pearl for two to five years to harvest it later, ”Farfan said.

Since the cultivation process is so efficient, cultured pearls are more widely available than their natural counterparts. So, instead of scarcity, their value comes from their symmetry and brilliance.

“It’s really the gemologist’s ability to match them that makes them something really special,” said Meyer. “For example, with earrings it’s about how well the pearls match in size and shape.”

Although pearl farming is flourishing today, it faces an uncertain future as do many other aquatic industries threatened by climate change.

Perilous pearls

Split mollusk shell on white packaging material

Since the pearls come from the shell material of the mollusks, such as mother of pearl, the fate of the pearls depends on the survival of the mollusks. Their survival will be called into question in the years to come by increasingly inhospitable living conditions. (Chris Meyer, Smithsonian)

Global water temperatures are increasing and local habitats are changing, which will affect mollusks and could threaten all types of bead making.

“Molluscs have optimal temperatures and environmental ranges, like you and I, where their bodily functions work best,” said Stewart Edie, marine paleobiologist and curator of fossil bivalves at the museum. “Global warming will alter these ranges, placing animals under stress, so we need to study how this stress affects the energy tradeoffs these animals will have to make. “

Species known to create gem-quality pearls may begin to redirect their energy to other biological needs. For example, the shells of saltwater molluscs weaken due to the acidification of the oceans. These animals might need to spend more nacre to repair their dissolving shells, which means less to trap irritants.

“It’s not a question of if, but by how much will saltwater pearls be affected by ocean acidification,” Farfan said, “And, ocean acidification is just l “One of the big problems that all shellfish face. There are also hurricanes, water quality and pollution problems and so on.”

Capture time

Cream shell on black background

Warming waters threaten all mollusks, including the pearl clams of the Pteriidae family. These species can adapt unexpectedly in response. (Smithsonian)

But by examining the pearls, researchers can see how mollusks react to environmental fluctuations.

“By using the pearls as mineral ‘time capsules’, we can examine how the environment around the mollusk influenced the pearl and go back to get a better picture of the environmental change,” Farfan said.

Currently, she and other scientists at the museum are studying pearls from freshwater and saltwater bodies to learn more about how their mineralogy evolves under changing temperatures and environments over time. seasons and years.

What they find could help them predict the fate of pearls and mollusks in the future.

“This is going to give us important information about the impact of environments on these very amazing gems,” said Farfan.

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Abigail Eisenstadt

Abigail Eisenstadt is a communications assistant at the Smithsonian National Museum of Natural History. She brings science to the public through the museum’s Communications and Public Affairs Office, where she follows media coverage, coordinates filming activities and writes for the museum’s blog, Smithsonian Voices. Abigail received her Masters in Science Journalism from Boston University. In her spare time, she is either outside or in the kitchen.

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