A pearl is an iridescent organic gemstone produced within the mantle of saltwater or freshwater mollusks. The following are the important or interesting characteristics of pearls.
Mother of Pearl
Mother of pearl, also known as nacre, is a composite material produced by some molluscs as an inner shell layer. Pearls are made of this strong, glistening and iridescent material. Most species of mollusc shells do not produce mother of pearl and therefore can't produce valuable pearls.
The foundational reason that pearls are valued as a gemstone is their iridescent. This means that they appear to be different colors depending on viewing angle and lighting conditions.
Pearls are valued according to their optical properties such as reflection, refraction, and diffraction. Pearls have a sparkly quality. A more valuable luster is produced by pearls with many thin layers of mother of pearl. In some cases, pearls may be chemically or physically treated in order to alter or enhance their luster. This may detract from the value of the pearl if it is detected.
Pearls come in a large number of colors such as white, pink, silver, beige, brown, green, blue, black, yellow, red, gold and purple. Traditionally, natural pearls that are white or more likely off-white are most valued.
Natural pearls are pearls that occur spontaneously in the wild. This occurs by accident and is not at all common such that natural pearls are rare and valuable. Pearls are formed when a mollusk is injured or invaded by a foreign substance such as sand. The mollusk repairs this damage by coating the area in layers of mother of pearl. Natural pearls are found by opening up a large number of mollusks, which kills the animal. In some cases, pearl hunting this is banned in certain areas, such as the rivers of UK, to prevent damage to threatened species.
A cultured pearl is a created by a farmer who "seeds" a mollusk with a tissue graft from a donor mollusk. Cultured pearls have a center that isn't made of mother of pearl but is covered by mother of pearl. A natural pearl has many layers of mother of pearl with no such center. The difference can be determined in a lab using specialized equipment that may also detect if the pearl is freshwater or saltwater and if the color has been modified. All else being equal, a cultured pearl is not as valuable as a natural pearl but still can have significant value. These are valued differently than natural pearls. For example, the unique colors of black cultured pearls cultivated in Tahiti are highly valued. Cultured pearls are French Polynesia’s largest export.
From the perspective of geologists or gemologists, all saltwater and freshwater mollusks can produce pearls. However, only a few species produce pearls that are iridescent with most geological pearls having an appearance that resembles porcelain. Therefore, when a geologist talks about pearls they aren't necessarily talking about the precious gemstones.
Fossilized pearls as old as about 200 million years have been found. Mollusks have been around for about 500 million years so older examples may be discovered at some point. Fossil pearls aren't valued as gems but generate the interest of museums and collectors of geological artifacts.
An imitation pearl is a relatively low value item that is made to look like a pearl using organic materials, particularly mother of pearl and inorganic materials such a paints, metals and plastics. These should not be confused with natural pearls or cultured pearls. Imitation pearls were produced in Venice from the 16th century onwards and were fashionable across Europe for several centuries. For example, the pearl in the well known painting Girl with a Pearl Earring by Johannes Vermeer is almost certainly an imitation pearl as its large size would make it priceless and well beyond the means of the artist.
Pearls are valued according to their shape. Valuable shapes include spherical and teardrop pearls. These are valued according to their symmetry. Non-spherical pearls are known as Baroque pearls and can be ovoid, curved or lumpy. The shape of cultured pearls can be influenced by the farmer. As such, shapes of natural pearls demonstrate more variety such that a large, perfectly shaped natural pearl can be extremely valuable. Ironically, low value pearls that have been artificially reshaped may also have a perfect shape. Generally speaking, a slightly odd shape is a sign that a pearl is authentic and unadulterated.
The weight of a pearl is a factor in its value. Pearls are often weighed with a traditional Japanese measurement known as momme with one momme being 3.75 grams.
Pearls are a little harder than a soft metal. For example, pure gold has a hardness of 2.5-3.0 but pearls have a hardness of 2.5–4.5 on the mohs scale. As another comparison, regular steel has a hardness of 4-4.5.
Natural and cultured pearls have a slightly rough texture and don't feel smooth. Feeling the surface of the pearl is one step that can be used to identify imitation pearls.
The value of natural pearls is rated according to factors such as size, color, shape, surface quality and luster. Assembling high quality pearls of a similar shape, quality and color for stands is difficult such that strands of natural pearls are extremely expensive. For example, in 1917 jeweler Pierre Cartier purchased a mansion on 5th avenue in New York in exchange for a strand of 128 natural pearls. It took the jeweler years to assemble the pearls for this strand. The mansion is now one of Cartier's flagship locations. There are equally impressive stories of valuable pearls from antiquity. For example, a single pearl was used to fund an entire military campaign by the Roman general Vitellius.(This building was purchased with a single strand of pearls)
The Pearl of Lao Tsu is the largest known pearl with a weight of 6.4 kilograms or 14.2 pounds. It is a non-iridescent natural pearl that has an interesting shape that supposedly looks like Lao Tzu, an ancient Chinese philosopher and writer. Due to its size and the folklore surrounding it, the pearl has been valued at up to $94,000,000.
Pearls are traditionally used in garments as an adornment. This is used to increase the value of a garment to signal social status and wealth.
Molluscs, or mollusks, are a category of about 85,000 living species of saltwater and freshwater animal. Most have shells but some do not. Only a few species such as saltwater pearl oysters and freshwater pearl mussels produce precious gemstones.(Black lip oyster, the source of Tahitian pearls)
There is some evidence that prehistorical societies engaged in pearl diving. As such, pearls may have been discovered and traded since before the beginning of recorded history. Cultured pearls were invented in China as early as the 13th century. However, most pearls sold before the 19th century were natural pearls such that they were viewed as amongst the most precious gemstones. In the 20th century, cultured pearl operations were scaled up and confusion reined amongst consumers about the differences and value of various types of pearls. Cultured pearls now dominate the market, with pearl hunting having declined in many parts of the world.
Ama are pearl collecting Japanese freedivers who are considered an iconic element of Japanese culture. The Ama are all women who follow traditions that may be as old as 2000 years. As late as the 1960s, they dove wearing only a loincloth without snorkeling or scuba gear. They wear only white as they believe it wards off sharks.
Again, the kingdom of heaven is like unto a merchant man, seeking goodly pearls: Who, when he had found one pearl of great price, went and sold all that he had, and bought it. ~Parable of the Pearl, Matthew 13:45-46, King James Version
It is often claimed that pearls represent purity owing to their white color. However, pearls are more commonly referenced as a symbol of wealth and greed. Pearls are also historically used to symbolize all that is admirable and valuable.
There have been two pearls that were the largest in the whole of history; both were owned by Cleopatra... She took one earring off and dropped the pearl in the vinegar, and when it was melted swallowed it...." Pliny, Natural History (IX.59.119-121; also Macrobius, Saturnalia, III.17.14-17)
An old myth or story recounts a wager between Cleopatra and Mark Antony as to who could spend the most on a banquet. As the story goes, Cleopatra wins this bet by dissolving a priceless pearl in vinegar and drinking it. This well known story symbolizes audacious wealth. Pearls can easily be damaged by vinegar as they are mostly composed of calcium carbonate. However, it is unlikely a large pearl would dissolve fast enough to impress dinner guests as in the story. In the modern era, pearls are ground up as an ingredient in various products, particularly cosmetics.
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