The material created by the mantle is called nacre. Nacre lines the inside of the shell. It's kind of like the oyster getting a splinter. The oyster's natural reaction is to cover up that irritant to protect itself. This eventually forms a pearl. So a pearl is a foreign substance covered with layers of nacre.
Most pearls that we see in jewelry stores are nicely rounded objects, which are the most valuable ones. Not all pearls turn out so well. Some pearls form in an uneven shape -- these are called baroque pearls. Pearls, as you've probably noticed, come in a variety of various colors, including white, black, gray, red, blue and green. Most pearls can be found all over the world, but black pearls are indigenous to the South Pacific.
Cultured pearls are created by the same process as natural pearls, but are given a slight nudge by pearl harvesters. To create a cultured pearl, the harvester opens the oyster shell and cuts a small slit in the mantle tissue. Small irritants are then inserted under the mantle. 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! Pearls are made by marine oysters and freshwater mussels as a natural defence against an irritant such as a parasite entering their shell or damage to their fragile body. The oyster or mussel slowly secretes layers of aragonite and conchiolin, materials that also make up its shell. This creates a material called nacre, also known as mother-of-pearl, which encases the irritant and protects the mollusc from it. When pearls are cultured commercially an irritant is manually inserted into a mollusc to promote the production of mother-of-pearl.
To make the structure strong, many layers of paper and glue are added and then allowed to dry. A similar process occurs when a mollusc makes a pearl. We have a similar immune response in the human body, called a granuloma. If this happens then the granuloma may need to be removed through surgery or chemical treatment. Sometimes a human granuloma will harden through calcification. This will cause the bundle of white blood cells to harden and turn white.
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It is mandatory to procure user consent prior to running these cookies on your website. Book Contact us. By Myfi Williams Pearls are seen as objects of beauty; we have used them for jewellery and decoration for hundreds of years. A macrophage.
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