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Speaker 1: Welcome to brain Stuff, a production of iHeartRadio Hey brain

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Speaker 1: Stuff Laurin vogel bomb here. Most jewelry is fashioned out

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Speaker 1: of precious metals and jewels that are made by physical

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Speaker 1: and chemical processes in the Earth, but pearls are made

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Speaker 1: inside of living creatures oysters. Pearls are the result of

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Speaker 1: a biological process and oyster's way of protecting itself from

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Speaker 1: foreign substances. Oysters are not the only type of mollusc

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Speaker 1: that can produce pearls. Clams and muscles can also produce them,

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Speaker 1: but it's much more rare. Most pearls are produced by

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Speaker 1: oysters in either fresh water or salt water environments. But

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Speaker 1: to understand how pearls are formed and oysters, you must

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Speaker 1: first understand and oyster's basic anatomy. Okay. An oyster is

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Speaker 1: a bivalve, which means that its shell is made of

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Speaker 1: two halves, which are called valves. The shells valves are

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Speaker 1: held together by an elastic ligament. The ligament is positioned

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Speaker 1: where the valves come together and usually keeps the valves

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Speaker 1: open so that the oyster can eat, but they can

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Speaker 1: be shut by a powerful abductor muscle inside the shell

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Speaker 1: if you've ever eaten an oyster or other bivalve. This

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Speaker 1: is the tough cylinder of tissue stuck to the inside

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Speaker 1: of the shell. Inside the shell, the oyster also has

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Speaker 1: a body consisting of its heart, gills, and digestive and

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Speaker 1: reproductive organs, plus its mantle. The mantle is a thin

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Speaker 1: layer of tissue that lines the inner part of the

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Speaker 1: oyster's shell. This organ has glands that extract minerals from

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Speaker 1: water and convert them to the building blocks of the

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Speaker 1: oyster's hard shell. Because as the oyster grows in size,

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Speaker 1: its shell must also grow. The mantles cretes the mineral

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Speaker 1: calcium carbonate, along with a type of protein that together

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Speaker 1: form the shell. A calcium carbonate is the same material

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Speaker 1: used to make chalk, eggs, shells, and our own bones,

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Speaker 1: and it makes up ninety eight percent of the shell.

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Speaker 1: It coats the underlying protein structure to form the shell's

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Speaker 1: hard surface, a sort of like pouring concrete over steel

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Speaker 1: beams to create a structure that's stronger than either material alone.

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Speaker 1: The oyster shell has different layers. The outermost layer is

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Speaker 1: a hard outer wrapping called the periostracum. The middle layer

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Speaker 1: is a set of structural struts, called the prismatic layer.

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Speaker 1: The innermost layer is the nacreous layer, also known as

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Speaker 1: the pearl layer or just mother of pearl. It's iridescent

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Speaker 1: and is sometimes used to make buttons or other ornamental items.

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Speaker 1: It also helps form pearls. The formation of a natural

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Speaker 1: pearl inside an oyster begins when a foreign substance slips

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Speaker 1: into the oyster between the mantle and its shell, which

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Speaker 1: irritates the mantle. It's kind of like the oyster getting

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Speaker 1: a splinter. The oyster's natural reaction is to cover up

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Speaker 1: the irtint by encapsulating the interloper, thereby protecting itself. The

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Speaker 1: mantle covers the irritint with layers of that same nacre

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Speaker 1: substance that's part of the shell, and these concentric layers

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Speaker 1: of nacre will eventually form a pearl. Some oyster species

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Speaker 1: are able to secrete three or four layers of nacre

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Speaker 1: a day, but each layer will be incredibly thin. Most

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Speaker 1: naked layers that make up a pearl will be as

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Speaker 1: thin as a thousandth of a millimeter that's one thirtieth

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Speaker 1: of an inch or one micron. It'll typically take an

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Speaker 1: oyster at least twenty four months to make a natural

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Speaker 1: pearl that's about five millimeters or one fifth of an

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Speaker 1: inch in diameter, which is about the height of twenty

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Speaker 1: stacked playing cards. It's commonly believed that pearls are formed

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Speaker 1: when a grain of sand enters an oyster. However, this

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Speaker 1: has recently been disputed as a myth. While it is

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Speaker 1: technically possible for a grain of sand to be at

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Speaker 1: the center of a pearl, the oyster species that produce

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Speaker 1: pearls are found on both sandy oceans and muddy freshwater floors,

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Speaker 1: and they have the ability to expel sand and other

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Speaker 1: small objects like little pieces of seashells. The majority of

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Speaker 1: natural pearls are formed in oysters as response to a

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Speaker 1: parasitic intruder. A parasitic organisms like drill worms will burrow

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Speaker 1: through the hard shell of an oyster and trigger its

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Speaker 1: mantle to secreate a barrier around the biological interloper. Either way,

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Speaker 1: the resulting pearl is a foreign substance covered with layers

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Speaker 1: of maker. The average natural pearl is about seven millimeters

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Speaker 1: or a quarter inch in diameter. Pearls that grow to

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Speaker 1: a size of ten millimeters or two fifthsphn inch or

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Speaker 1: more are rare and expensive. In general, the larger a

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Speaker 1: natural pearl, the more valuable it's considered to be. Natural

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Speaker 1: pearls come in a variety of colors, including white, black, gray, red, blue,

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Speaker 1: and green. Most pearls can be found all over the world,

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Speaker 1: but black pearls are indigenous to the Sepsi. A pearls

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Speaker 1: can be uneven in shape. In jewelry, these are called

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Speaker 1: baroque pearls. This happens when the nacre layers encounter resistance

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Speaker 1: during formation, often because the pearl is lodged in muscle

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Speaker 1: tissue within the oyster. Natural pearls that are pretty much

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Speaker 1: perfectly round are more often used in jewelry and are

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Speaker 1: considered more valuable. Meanwhile, cultured pearls are created by the

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Speaker 1: same process as natural pearls, but require intervention by pearl harvesters.

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Speaker 1: To create a cultured pearl, the harvester opens the oyster

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Speaker 1: shell and cuts a small slit in the mantle tissue.

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Speaker 1: A small ear tints are then inserted under the mantle

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Speaker 1: and the nakere tissue begins forming a pearl. Some cultured

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Speaker 1: pearls are created using a sort of grafting process in

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Speaker 1: which a pearl nucleus is inserted into an oyster, providing

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Speaker 1: the seed for the growth of a new pearl, and

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Speaker 1: in some cases, simply cutting the mantle is enough to

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Speaker 1: induce the nacre secretion that produces a pearl, and an

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Speaker 1: irritant doesn't have to be inserted. In general, cultured pearls

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Speaker 1: are far less expensive than natural ones because they can

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Speaker 1: be produced in mass to better meet demand, but both

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Speaker 1: kinds of pearls are still real pearls gems created by animals.

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Speaker 1: Today's episode is based on the article how do Oysters

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Speaker 1: make Pearls? On how Stuffworks dot Com written by Lori L. Dove.

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Speaker 1: The brain Stuff is production of iHeartRadio in partnership with

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Speaker 1: how Stuffworks dot Com and is produced by Tyler Klang.

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