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  • Pearls have been a symbol of elegance

  • and class for centuries.

  • The Maharajas of India and European queens

  • adorned themselves with pearls, a symbol of their prestige.

  • At 2018's Catholic Church-inspired Met Gala,

  • celebrities walked the red carpet

  • dripping in pearls.

  • Uma Thurman's dress had over 3,000 white pearls sewn to it,

  • while Rihanna's pope-inspired outfit

  • was encrusted in pearls.

  • At the 2019 Grammys, Cardi B

  • was basically dressed like an oyster.

  • The most expensive pearl ever sold

  • was Marie Antoinette's pendant.

  • It sold for $32 million in a 2018 auction.

  • But what is it that makes pearls so expensive?

  • Marie Antoinette's pearl was part

  • of a diamond-studded pendant,

  • and it has important historical significance,

  • which increased its value.

  • But there are several other factors

  • that determine the value of a pearl.

  • Tom Moses: Assessing the value of a pearl

  • is probably the most complex gem to assess.

  • Narrator: That's Tom Moses.

  • He's a gemologist at the Gemological Institute of America

  • where he oversees diamond grading,

  • colored stone identification, and pearl identification.

  • He says that part of the reason

  • the Marie Antoinette pearl is worth so much

  • is because it's a natural pearl,

  • which brings us to one quality

  • that determines a pearl's value.

  • Natural versus cultured.

  • Natural pearls are hard to find.

  • They're rare, and this makes them worth more money.

  • But let's rewind for a second.

  • What is a natural pearl,

  • and how are they formed?

  • Natural pearls form when some kind of irritant,

  • usually a small organism,

  • makes its way into the shell of a mollusk

  • like an oyster or a mussel.

  • To protect itself from the invader,

  • the mollusk starts to coat the debris with nacre,

  • or mother-of-pearl, the same material

  • that lines the inner layer of its shell.

  • It continues doing this,

  • and the irritant grows into a shiny pearl.

  • Cultured pearls are formed by the same process,

  • but instead of the irritant entering the shell accidentally,

  • it's put there intentionally by a human.

  • Pearl farmers insert a piece of mollusk tissue,

  • which is called donor tissue,

  • into the shell of the oyster

  • where they want the pearl to grow.

  • This triggers the oyster's defense response,

  • and it starts coating that piece of tissue with nacre.

  • The vast majority of pearls on the market

  • are cultured pearls.

  • The Gemological Institute of America

  • uses X-rays to tell if a pearl is natural or cultured.

  • If you look closely at these two images,

  • you can see the difference.

  • Moses: Think about the layers of an onion.

  • So a natural pearl would have all of those

  • concentric layers of growth from the very inside out.

  • Narrator: A cultured pearl, on the other hand,

  • is like an orange, with a large center

  • and a thinner layer of pearl growth around that.

  • The large center is the manmade irritant

  • placed in the shell to encourage nacre formation.

  • Cultured pearls date all the way back to around 500 AD

  • in China. However, in 1893, the Japanese-born

  • kichi Mikimoto streamlined the process

  • and eventually created perfectly round pearls.

  • Today, Mikimoto is widely considered

  • the grandfather of cultured pearls.

  • He used Akoya pearls, which are the traditional

  • white round pearls you're probably familiar with.

  • By the 1920s, cultured pearls became

  • more commercially available, which made them more affordable

  • and accessible to people who weren't royalty.

  • But just because you can grow a cultured pearl

  • doesn't mean it's an easy process.

  • Pearl farmers pry open the mollusk shell

  • just enough to implant the piece of foreign tissue,

  • then they put the oysters back in the water

  • and wait anywhere from six months to two years

  • for pearls to form,

  • and not every pearl comes out the same,

  • which brings us to another quality

  • that can make one pearl worth more than another.

  • Size.

  • The larger the pearl,

  • the more valuable, just like any other gem.

  • Narrator: The size of the pearl largely depends

  • on the size of the mollusk.

  • Certain oysters grow bigger than others

  • and can, therefore, make bigger pearls.

  • For example, Akoya pearls can only grow

  • to about 9 or 10 millimeters in diameter,

  • but South Sea pearls and black Tahitian pearls

  • can reach a diameter of around 15 or 16 millimeters.

  • The larger size makes South Sea pearls

  • and black pearls the most valuable type of pearl.

  • On Mikimoto's website,

  • this strand of South Sea cultured pearls

  • is selling for $32,000.

  • The other notable difference between pearl types

  • is the color.

  • Sometimes this goes hand in hand with size

  • because the pearl's color is determined

  • mostly by the mollusk it comes from.

  • Tahitian black pearls are black because the inside

  • of the Pinctada margaritifera oyster is black,

  • but colors can vary slightly

  • based on the culturing process as well.

  • The main reason for the color difference

  • is the species of the mollusk.

  • Another very interesting influence

  • is when a pearl is cultured,

  • there is a donor tissue used from another living mollusk,

  • and depending on the color of that tissue,

  • it will influence the color of the final cultured pearl.

  • Narrator: Take for example Akoya pearls.

  • These are all white pearls,

  • but the shade of white can still vary.

  • Some strands might be slightly more pink,

  • while others have more of a greenish tint.

  • Tom says that pinker pearls are typically preferred

  • over green hues.

  • Along with size and color, the shape and surface

  • of a pearl can have an impact on its value.

  • Typically the rounder and smoother, the better.

  • And finally, perhaps the hardest variable

  • to measure: luster.

  • Luster is essentially the way a pearl reflects light.

  • The shinier the pearl, the better.

  • But it's hard to tell how shiny a pearl is

  • unless you have other pearls to compare it to.

  • That's why Tom and the rest of the Gemological Institute

  • have a collection of sample strands for comparison.

  • That way they can look at how one strand of pearls

  • compares to another and see where it falls

  • on the luster scale.

  • The quality of a pearl's luster

  • is influenced by the layers of nacre that coat the center.

  • One way to think of it

  • is like the tiles of a roof.

  • Picture a roof with all the tiles lined

  • up so that everything fits together well.

  • If you translate that to a pearl,

  • it would result in a nice, high-luster pearl.

  • A dull, low-luster pearl would be more like a roof

  • with broken and fragmented tiles that don't line up.

  • When you take into consideration

  • all of these factors, finding or creating

  • the perfect pearl is an art,

  • and the fact remains they're grown inside an animal,

  • so it's impossible to have complete control

  • over how and when they form,

  • especially in the wild.

  • So if you ever bite down on something hard

  • while you're eating an oyster,

  • take a look at it before you chuck it.

  • It might be more than a piece of sand.

Pearls have been a symbol of elegance

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真珠はなぜ高価なのか|高価な理由 (Why Pearls Are So Expensive | So Expensive)

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    PENG に公開 2021 年 01 月 14 日
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