Pearl

Apearlis a hard, glistening object produced within the soft tissue (specifically themantle) of a livingshelledmolluskor another animal, such as fossilconulariids. Just like the shell of a mollusk, a pearl is composed ofcalcium carbonate(mainlyaragoniteor a mixture of aragonite andcalcite)in minute crystalline form, which has deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other shapes, known asbaroque pearls, can occur. The finest quality of natural pearls have been highly valued asgemstonesand objects ofbeautyfor many centuries. Because of this,pearlhas become ametaphorfor something rare, fine, admirable and valuable.
The most valuable pearls occur spontaneously in the wild, but are extremely rare. These wild pearls are referred to asnaturalpearls.Culturedorfarmedpearls frompearl oystersand freshwater mussels make up the majority of those currently sold.Imitation pearlsare also widely sold in inexpensive jewelry. Pearls have been harvested and cultivated primarily for use injewelry, but in the past were also used to adorn clothing. They have also been crushed and used in cosmetics, medicines and paint formulations.
Whether wild or cultured, gem-quality pearls are almost alwaysnacreousandiridescent, like the interior of the shell that produces them. However, almost all species of shelled mollusks are capable of producing pearls (technically "calcareous concretions") of lesser shine or less spherical shape. Although these may also be legitimately referred to as "pearls" by gemological labs and also under U.S.Federal Trade Commissionrules,and are formed in the same way, most of them have no value except as curiosities.
TheEnglishwordpearlcomes from theFrenchperle, originally from theLatinperna'leg', after the ham- or mutton leg-shapedbivalve.
The scientific name for the family of pearl-bearing oysters,Margaritiferidaecomes from theOld Persianword for pearl*margārīta-which is the source of the English nameMargaret.
All shelled mollusks can, by natural processes, produce some kind of "pearl" when an irritating microscopic object becomes trapped within its mantle folds, but the great majority of these "pearls" are not valued asgemstones. Nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluskanbivalvesorclams. A nacreous pearl is made from layers ofnacre, by the same living process as is used in the secretion of themother of pearlwhich lines the shell.
Natural (or wild) pearls, formed without human intervention, are very rare. Many hundreds of pearl oysters or mussels must be gathered and opened, and thus killed, to find even one wild pearl; for many centuries, this was the only way pearls were obtained, and why pearls fetched such extraordinary prices in the past.Cultured pearlsare formed in pearl farms, using human intervention as well as natural processes.
One family of nacreous pearl bivalves – thepearl oyster– lives in the sea,  while the other – a very different group ofbivalves– lives in freshwater; these are the rivermusselssuch as thefreshwater pearl mussel. Saltwater pearls can grow in several species ofmarinepearloystersin thefamilyPteriidae. Freshwater pearls grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the familiesUnionidaeandMargaritiferidae.
The uniquelusterof pearls depends upon thereflection,refraction, anddiffractionof light from thetranslucentlayers. The thinner and more numerous the layers in the pearl, the finer the luster. Theiridescencethat pearls display is caused by the overlapping of successive layers, which breaks up light falling on the surface. In addition, pearls (especiallycultured freshwater pearls) can be dyed yellow, green, blue, brown, pink, purple, or black. The most valuable pearls have a metallic, highly reflective luster.
Because pearls are made primarily of calcium carbonate, they can be dissolved invinegar. Calcium carbonate is susceptible to even a weak acid solution because the crystals react with theacetic acidin the vinegar to formcalcium acetateandcarbon dioxide.
Freshwater and saltwater pearls may sometimes look quite similar, but they come from different sources.
Freshwater pearls form in various species of freshwater mussels, familyUnionidae, which live in lakes, rivers, ponds and other bodies of fresh water. Thesefreshwater pearl musselsoccur not only in hotter climates, but also in colder, more temperate areas such asScotland(where they are protected under law).Most freshwatercultured pearlssold today come from China.
Saltwater pearls grow within pearl oysters, familyPteriidae, which live in oceans. Saltwaterpearl oystersare usually cultivated in protectedlagoonsor volcanic atolls.
The mollusk's mantle (protective membrane) deposits layers ofcalcium carbonate(CaCO3) in the form of themineralaragoniteor a mixture of aragonite and calcite (polymorphs with the same chemical formula, but different crystal structures) held together by an organic horn-like compound calledconchiolin. The combination of aragonite and conchiolin is callednacre, which makes up mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case. Typical stimuli include organic material, parasites, or even damage that displaces mantle tissue to another part of the mollusk's body. These small particles or organisms gain entry when the shell valves are open for feeding or respiration. In cultured pearls, the irritant is typically an introduced piece of the mantle epithelium, with or without a spherical bead (beaded or beadless cultured pearls).
Natural pearls are nearly 100% calcium carbonate andconchiolin. It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk and settles inside the shell. The mollusk, irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant. This secretion process is repeated many times, thus producing a pearl. Natural pearls come in many shapes, with perfectly round ones being comparatively rare.
Typically, the build-up of a natural pearl consists of a brown central zone formed by columnar calcium carbonate (usually calcite, sometimes columnar aragonite) and a yellowish to white outer zone consisting of nacre (tabular aragonite). In a pearl cross-section such as the diagram, these two different materials can be seen. The presence of columnar calcium carbonate rich in organic material indicates juvenile mantle tissue that formed during the early stage of pearl development. Displaced living cells with a well-defined task may continue to perform their function in their new location, often resulting in acyst. Such displacement may occur via an injury. The fragile rim of the shell is exposed and is prone to damage and injury. Crabs, other predators and parasites such as worm larvae may produce traumatic attacks and cause injuries in which some external mantle tissue cells are disconnected from their layer. Embedded in the conjunctive tissue of the mantle, these cells may survive and form a small pocket in which they continue to secrete calcium carbonate, their natural product. The pocket is called a pearl sac, and grows with time by cell division. The juvenile mantle tissue cells, according to their stage of growth, secrete columnar calcium carbonate from pearl sac's inner surface. In time, the pearl sac's external mantle cells proceed to the formation of tabular aragonite. When the transition to nacre secretion occurs, the brown pebble becomes covered with a nacreous coating. During this process, the pearl sac seems to travel into the shell; however, the sac actually stays in its original relative position the mantle tissue while the shell itself grows. After a couple of years, a pearl forms and the shell may be found by a lucky pearl fisher.
Cultured pearls are the response of the shell to a tissue implant. A tiny piece of mantle tissue (called agraft) from a donor shell is transplanted into a recipient shell, causing a pearl sac to form into which the tissue precipitates calcium carbonate. There are a number of methods for producing cultured pearls: using freshwater or seawater shells, transplanting the graft into the mantle or into the gonad, and adding a spherical bead as a nucleus. Most saltwater cultured pearls are grown with beads. Trade names of cultured pearls are Akoya (阿古屋), white or golden South sea, and blackTahitian. Most beadless cultured pearls are mantle-grown in freshwater shells in China, and are known as freshwater cultured pearls.
Cultured pearls can be distinguished from natural pearls byX-rayexamination.Nucleated cultured pearls are often 'preformed' as they tend to follow the shape of the implanted shell bead nucleus. After a bead is inserted into the oyster, it secretes a few layers of nacre around the bead; the resulting cultured pearl can then be harvested in as few as twelve to eighteen months.
When a cultured pearl with a bead nucleus is X-rayed, it reveals a different structure to that of a natural pearl. A beaded cultured pearl shows a solid center with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings. A beadless cultured pearl (whether of freshwater or saltwater origin) may show growth rings, but also a complex central cavity, witness of the first precipitation of the young pearl sac.
Some imitation pearls (also called shell pearls) are simply made ofmother-of-pearl,coralorconchshell, while others are made from glass and are coated with a solution containing fish scales calledessence d'Orient.
A well-equippedgem testing laboratorycan distinguish natural pearls from cultured pearls by using gemologicalX-rayequipment to examine the center of a pearl. With X-rays it is possible to see the growth rings of the pearl, where the layers of calcium carbonate are separated by thin layers of conchiolin. The differentiation of natural pearls from non-beaded cultured pearls can be very difficult without the use of this X-ray technique.
Natural andcultured pearlscan be distinguished from imitation pearls using amicroscope. Another method of testing for imitations is to rub two pearls against each other. Imitation pearls are completely smooth, but natural and cultured pearls are composed of nacre platelets, making both feel slightly gritty.
Fine quality natural pearls are very rare jewels. Their values are determined similarly to those of other precious gems, according to size, shape, color, quality of surface, orient and luster.
Single natural pearls are often sold as collectors' items, or set as centerpieces in unique jewelry. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars. (In 1917, jewelerPierre Cartierpurchased the Fifth Avenue mansion that is now the New York Cartier store in exchange for a matched double strand of natural pearls Cartier had been collecting for years; at the time, it was valued at US$1 million.)
The introduction and advance of the cultured pearl hit the pearl industry hard. Pearl dealers publicly disputed the authenticity of these new cultured products, and left many consumers uneasy and confused about their much lower prices. Essentially, the controversy damaged the images of both natural and cultured pearls. By the 1950s, when a significant number of women in developed countries could afford their own cultured pearl necklace, natural pearls were reduced to a small, exclusive niche in the pearl industry.
Previously, natural pearls were found in many parts of the world. Present day natural pearling is confined mostly to thePersian Gulf, in seas offBahrain. Australia also has one of the world's last remaining fleets of pearl diving ships. Australian pearl divers dive for south sea pearl oysters to be used in the cultured south sea pearl industry. The catch of pearl oysters is similar to the numbers of oysters taken during the natural pearl days. Hence significant numbers of natural pearls are still found in the Australian Indian Ocean waters from wild oysters. X-ray examination is required to positively verify natural pearls found today.
Akeshi pearlis a pearl composed entirely of nacre and results from mishaps in the culturing process.  Most are quite small, typically only a few millimeters in diameter, and are often irregular in shape. In seeding a cultured pearl, a piece of mantle muscle from a sacrificed oyster is placed with a bead of mother of pearl within a host oyster. If the piece of mantle should slip off the bead, a keshi pearl forms of baroque shape about the mantle piece. Therefore, while a keshi pearl could be considered superior to cultured pearls with a mother of pearl bead center, in the cultured pearl industry the oyster's resources used to create a mistaken all-nacre baroque pearl is a drain on the production of the intended round cultured pearl. Therefore, the pearl industry is making ongoing attempts to improve culturing technique so that keshi pearls do not occur. All-nacre pearls may one day be limited to natural found pearls.Today many "keshi" pearls are actually intentional, with post-harvest shells returned to the water to regenerate a pearl in the existing pearl sac.
Tahitian pearls, frequently referred to as black pearls,are highly valued because of their rarity; the culturing process for them dictates a smaller volume output and they can never be mass-produced because, in common with most sea pearls, the oyster can only be nucleated with one pearl at a time, while freshwater mussels are capable of multiple pearl implants. Before the days of cultured pearls, black pearls were rare and highly valued for the simple reason that white pearl oysters rarely produced naturally black pearls, and black pearl oysters rarely produced any natural pearls at all.
Since the development of pearl culture technology, the black pearl oystersPinctada margaritiferafound inTahitiand many other Pacific islands including theCook IslandsandFijiare being extensively used for producing cultured pearls. The rarity of the black cultured pearl is now a "comparative" issue. The black cultured pearl is rare when compared to Chinese freshwater cultured pearls, and Japanese and Chinese akoya cultured pearls, and is more valuable than these pearls. However, it is more abundant than the South Sea pearl, which is more valuable than the black cultured pearl. This is simply because the black pearl oysterPinctada margaritiferais far more abundant than the elusive, rare, and larger south sea pearl oysterPinctada maxima, which cannot be found in lagoons, but which must be dived for in a rare number of deep ocean habitats or grown in hatcheries.
Natural black pearls are rare, with black pearls having a body color that may be assessed as silver, silver blue, gold, brown-black, green-black, or black.
Black cultured pearls from the black pearl oyster –Pinctada margaritifera– are not South Sea pearls, although they are often mistakenly described as black South Sea pearls. In the absence of an official definition for the pearl from the black all use to, these pearls are usually referred to as "black pearls".
The correct definition of a South Sea pearl – as described by CIBJO and GIA – is a pearl produced by thePinctada maximapearl oyster. South Sea pearls are the color of their hostPinctada maximaoyster – and can be white, silver, pink, gold, cream, and any combination of these basic colors, including overtones of the various colors of the rainbow displayed in the pearl nacre of the oyster shell itself.
South Sea pearls are the largest and rarest of the cultured pearls – making them the most valuable.Prized for their exquisitely beautiful 'orient' or lustre, South Sea pearls are now farmed in various parts of the world where thePinctada maximaoysters can be found, with the finest South Sea pearls being produced byPaspaleyalong the remote coastline of North-Western Australia.White and silver colored South Sea pearls tend to come from theBroomearea of Australia, while golden colored ones are more prevalent in the Philippines and Indonesia.
A farm in theGulf of California, Mexico, is culturing pearls from the black lippedPinctada mazatlanicaoysters and the rainbow lippedPteria sternaoysters.Also called Concha Nácar, the pearls from these rainbow lipped oysters fluoresce red underultravioletlight.
Biologically speaking, under the right set of circumstances, almost any shelled mollusk can produce some kind of pearl. However, most of these molluskan pearls have no luster oriridescence. The great majority of mollusk species produce pearls which are not attractive, and are sometimes not even very durable. Such pearls usually have no value at all, except perhaps to a scientist or collector, or as a curiosity. These objects used to be referred to as "calcareous concretions" by some gemologists, even though amalacologistwould still consider them to be pearls. Valueless pearls of this type are sometimes found in ediblemussels, edibleoysters,escargotsnails, and so on.  The GIA and CIBJO now simply use the term 'pearl' (or, where appropriate, the more descriptive term 'non-nacreous pearl') when referring to such itemsand, under Federal Trade Commission rules, various mollusk pearls may be referred to as 'pearls', without qualification.
A few species produce pearls that can be of interest as gemstones. These species include the bailer shellMelo, thegiant clamTridacna, variousscallopspecies, Pen shellsPinna, and theHaliotis irisspecies of abalone. Pearls of abalone arecultured pearls, or blister pearls, unique toNew Zealandwaters, and are commonly referred to as 'blue pearls'. They are admired for their luster and naturally bright vibrant colors that are often compared toopal. Another example is the conch pearl (sometimes referred to simply as the 'pink pearl'), which is found very rarely growing between the mantle and the shell of the queenconchor pink conch,Strombus gigas, a large sea snail or marinegastropodfrom theCaribbean Sea. These pearls, which are often pink in color, are a by-product of the conch fishing industry, and the best of them display a shimmering optical effect related tochatoyanceknown as 'flame structure'.
Somewhat similar gastropod pearls, this time more orange in hue, are (again very rarely) found in the horse conchTriplofusus papillosus.
The second largest pearl known was found in thePhilippinesin 1934 and is known as thePearl of Lao Tzu. It is a naturally occurring, non-nacreous, calcareous concretion (pearl) from agiant clam. Because it did not grow in a pearl oyster it is not pearly; instead the surface is glossy like porcelain. Other pearls from giant clams are known to exist, but this is a particularly large one weighing 14 lb (6.4 kg).
The largest known pearl (also from a giant clam) is thePearl of Puerto, also found in the Philippines by a fisherman fromPuerto Princesa,Palawan Island. The enormous pearl is 30 cm wide (1 ft), 67 cm long (2.2 ft) and weighs 75 lb (34 kg).
The ancient chronicleMahavamsamentions the thriving pearl industry in the port of Oruwella in the Gulf of Mannar inSri Lanka. It also records that eight varieties of pearls accompaniedPrince Vijaya's embassy to the Pandyan king as well as kingDevanampiya Tissa's embassy toEmperor Ashoka.Pliny the Elder(23–79 AD) praised the pearl fishery of the Gulf as most productive in the world.
For thousands of years, seawater pearls were retrieved by divers in theIndian Oceanin areas such as thePersian Gulf, the Red Sea and theGulf of Mannar.Evidence also suggest aprehistoricorigin to pearl diving in these regions.Starting in theHan dynasty(206 BC–220 AD), theChinesehunted extensively for seawater pearls in theSouth China Sea, particularly in what is nowTolo HarbourinHong Kong.Tankapearl divers of twelfth century China attached ropes to their waists in order to be safely brought back up to the surface.
When Spanish conquistadors arrived in the Western Hemisphere, they discovered that around the islands ofCubaguaandMargarita, some 200 km north of theVenezuelancoast, was an extensive pearl bed (a bed of pearl oysters). One discovered and named pearl,La Peregrina pearl, was offered toPhilip II of Spainwho intended to give it as a gift for his daughter on the occasion of her marriage, but the King found it so beautiful that he kept it for himself. Later, he elevated it to be part of the Spanish Crown Jewel. From then on, the pearl was recorded in every royal inventory for more than 200 years.  According toGarcilasso de la Vega, who says that he saw La Peregrina at Seville in 1607,this was found atPanamain 1560 by aslaveworker who was rewarded with his liberty, and his owner with the office of alcalde of Panama.
Margarita pearls are extremely difficult to find today and are known for their unique yellowish color. 
Before the beginning of the 20th century,pearl huntingwas the most common way of harvesting pearls. Divers manually pulled oysters from ocean floors and river bottoms and checked them individually for pearls. Not all mussels and oysters produce pearls. In a haul of three tons, only three or four oysters will produce perfect pearls.
Pearls were one of the attractions which drew Julius Caesar to Britain.They are, for the most part, freshwater pearls from mussels. Pearling was banned in the U.K. in 1998 due to the endangered status of river mussels.Discovery and publicity about the sale for a substantial sum of theAbernethy pearlin theRiver Tayhad resulted in heavy exploitation of mussel colonies during the 1970s and 80s by weekend warriors.When it was permitted it was carried on mainly byScottish Travellerswho found pearls varied from river to river with theRiver Oykelin the Highlands being noted for the finest rose-pink pearls.There are two firms in Scotland that are licensed to sell pre-1998 freshwater pearls.
Today, the cultured pearls on the market can be divided into two categories. The first category covers the beaded cultured pearls, including akoya, South Sea and Tahiti. These pearls are gonad grown, and usually one pearl is grown at a time. This limits the number of pearls at a harvest period. The pearls are usually harvested after one year for akoya, 2–4 years for Tahitian and South Sea, and 2–7 years for freshwater. This perliculture process was first developed by the British biologistWilliam Saville-Kentwho passed the information along to Tatsuhei Mise and Tokichi Nishikawa fromJapan.
The second category includes the non-beaded freshwater cultured pearls, like the Biwa or Chinese pearls. As they grow in the mantle, where on each wing up to 25 grafts can be implanted, these pearls are much more frequent and saturate the market completely. An impressive improvement in quality has taken place over ten years when the former rice-grain-shaped pebbles are compared with the near round pearls of today. Later, large near perfect round bead nucleated pearls up to 15mm in diameter have been produced with metallic luster.
The nucleus bead in a beaded cultured pearl is generally a polished sphere made from freshwatermusselshell. Along with a small piece of mantle tissue from another mollusk (donor shell) to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusk. In freshwater perliculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. South Sea and Tahitian pearl oysters, also known asPinctada maximaandPinctada margaritifera, which survive the subsequent surgery to remove the finished pearl, are often implanted with a new, larger beads as part of the same procedure and then returned to the water for another 2–3 years of growth.
Despite the common misperception,Mikimotodid not discover the process of pearl culture. The accepted process of pearl culture was developed by the British BiologistWilliam Saville-Kentin Australia and brought to Japan by Tokichi Nishikawa and Tatsuhei Mise. Nishikawa was granted the patent in 1916, and married the daughter of Mikimoto. Mikimoto was able to use Nishikawa's technology. After the patent was granted in 1916, the technology was immediately commercially applied to akoya pearl oysters in Japan in 1916. Mise's brother was the first to produce a commercial crop of pearls in the akoya oyster. Mitsubishi's Baron Iwasaki immediately applied the technology to the south sea pearl oyster in 1917 in the Philippines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured south sea pearl – although it was not until 1928 that the first small commercial crop of pearls was successfully produced.
The original Japanese cultured pearls, known as akoya pearls, are produced by a species of small pearl oyster,Pinctada fucata martensii, which is no bigger than 6 to 8 cm (2.4 to 3.1 in) in size, hence akoya pearls larger than 10 mm in diameter are extremely rare and highly priced. Today, a hybrid mollusk is used in both Japan and China in the production of akoya pearls.
Cultured Pearls were sold in cans for the export market. These were packed in Japan by the I.C.P. Canning Factory (International Pearl Company L.T.D.) in Nagasaki Pref. Japan.
Mitsubishi commenced pearl culture with the South Sea pearl oyster in 1916, as soon as the technology patent was commercialized. By 1931 this project was showing signs of success, but was upset by the death of Tatsuhei Mise. Although the project was recommenced after Tatsuhei's death, the project was discontinued at the beginning of WWII before significant productions of pearls were achieved.
After WWII, new south sea pearl projects were commenced in the early 1950s atKuri Bayand Port Essington in Australia, andBurma. Japanese companies were involved in all projects using technicians from the original Mitsubishi South Sea pre-war projects. Kuri Bay is now the location of one of the largest and most well-known pearl farms owned byPaspaley, the biggest producer of South Sea pearls in the world.
In 2010, China overtook Japan in akoya pearl production.Japan has all but ceased its production of akoya pearls smaller than 8 mm.Japan maintains its status as a pearl processing center, however, and imports the majority of Chinese akoya pearl production. These pearls are then processed (often simply matched and sorted), relabeled as product of Japan, and exported.
In the past two decades, cultured pearls have been produced using larger oysters in the southPacificandIndian Ocean. The largest pearl oyster is thePinctada maxima, which is roughly the size of a dinner plate. South Sea pearls are characterized by their large size and warm luster. Sizes up to 14 mm in diameter are not uncommon. In 2013, Indonesia Pearlsupplied 43 percent of South Sea Pearls international market.The other significant producers areAustralia,Philippines,MyanmarandMalaysia.
In 1914, pearl farmers began growingcultured freshwater pearlsusing the pearl mussels native toLake Biwa. This lake, the largest and most ancient in Japan, lies near the city ofKyoto. The extensive and successful use of the Biwa Pearl Mussel is reflected in the nameBiwa pearls, a phrase which was at one time nearly synonymous with freshwater pearls in general. Since the time of peak production in 1971, when Biwa pearl farmers produced six tons of cultured pearls, pollution has caused the virtual extinction of the industry. Japanese pearl farmers recentlycultured a hybrid pearl mussel – a cross between Biwa Pearl Mussels and a closely related species from China,Hyriopsis cumingi, inLake Kasumigaura. This industry has also nearly ceased production, due to pollution. Currently, theBelpearlcompany based out of Kobe, Japan continues to purchase the remaining Kasumiga-ura pearls.
Japanese pearl producers also invested in producing cultured pearls withfreshwater musselsin the region ofShanghai,China. China has since become the world's largest producer of freshwater pearls, producing more than 1,500 metric tons per year (in addition to metric measurements,Japanese units of measurementsuch as the kan and momme are sometimes encountered in the pearl industry).
Led by pearl pioneerJohn Latendresseand his wife Chessy, the United States began farmingcultured freshwater pearlsin the mid-1960s.National Geographicmagazine introduced the American cultured pearl as a commercial product in their August 1985 issue. The Tennessee pearl farm has emerged as a tourist destination in recent years, but commercial production of freshwater pearls has ceased.
For many cultured pearl dealers and wholesalers, the preferred weight measure used for loose pearls and pearl strands is themomme. Momme is a weight measure used by the Japanese for centuries.  Today, momme weight is still the standard unit of measure used by most pearl dealers to communicate with pearl producers and wholesalers. One momme corresponds to 1/1000 kan.  Reluctant to give up tradition, the Japanese government formalized the kan measure in 1891 as being exactly 3.75 kilograms or 8.28 pounds.  Hence, 1 momme = 3.75 grams or 3750 milligrams.
In the United States, during the 19th and 20th centuries, through trade with Japan in silk cloth the momme became a unit indicating the quality of silk cloth.
Though millimeter size range is typically the first factor in determining a cultured pearl necklace's value, the momme weight of pearl necklace will allow the buyer to quickly determine if the necklace is properly proportioned. This is especially true when comparing the larger south sea and Tahitian pearl necklaces.
The value of the pearls in jewelry is determined by a combination of the luster, color, size, lack of surface flaw and symmetry that are appropriate for the type of pearl under consideration. Among those attributes, luster is the most important differentiator of pearl quality according to jewelers.
All factors being equal, however, the larger the pearl the more valuable it is. Large, perfectly round pearls are rare and highly valued. Teardrop-shaped pearls are often used in pendants.
Pearls are generally of spherical shapes. Perfectly round pearls are the rarest and most valuable shape. Semi-rounds are also used in necklaces or in pieces where the shape of the pearl can be disguised to look like it is a perfectly round pearl. Button pearls are like a slightly flattened round pearl and can also make a necklace, but are more often used in single pendants or earrings where the back half of the pearl is covered, making it look like a larger, rounder pearl.
Pear-shaped pearls sometimes look like teardrop pearls and are most often seen in earrings, pendants, or as a center pearl in a necklace. Baroque pearls have a different appeal; they are often highly irregular with unique and interesting shapes. They are also commonly seen in necklaces. Circled pearls are characterized by concentric ridges, or rings, around the body of the pearl.
In general, cultured pearls are less valuable than natural pearls, whereas imitation pearls have almost no value. One way that jewelers can determine whether a pearl is cultured or natural is to have a gemlab perform an X-ray examination of the pearl. If X-rays reveals a nucleus, the pearl is likely a bead-nucleated saltwater pearl. If no nucleus is present, but irregular and small dark inner spots indicating a cavity are visible, combined with concentric rings of organic substance, the pearl is likely a cultured freshwater.Cultured freshwater pearlscan often be confused for natural pearls which present as homogeneous pictures which continuously darken toward the surface of the pearl. Natural pearls will often show larger cavities where organic matter has dried out and decomposed.
There is a special vocabulary used to describe the length of pearl necklaces. While most other necklaces are simply referred to by their physical measurement, pearl necklaces are named by how low they hang when worn around the neck. Acollar, measuring 10 to 13 inches or 25 to 33 cm in length, sits directly against the throat and does not hang down the neck at all; collars are often made up of multiple strands of pearls.Pearl chokers, measuring 14 to 16 inches or 35 to 41 cm in length, nestle just at the base of the neck. A strand called aprincess length, measuring 17 to 19 inches or 43 to 48 cm in length, comes down to or just below the collarbone. Amatinee length, measuring 20 to 24 inches or 50 to 60 cm in length, falls just above the breasts. Anopera length, measuring 28 to 35 inches or 70 to 90 cm in length, will be long enough to reach the breastbone or sternum of the wearer; and longer still, apearl rope, measuring more than 45 inches or 115 cm in length, is any length that falls down farther than anopera.
Necklaces can also be classified as uniform, or graduated. In a uniform strand of pearls, all pearls are classified as the same size, but actually fall in a range. A uniform strand of akoya pearls, for example, will measure within 0.5 mm. So a strand will never be 7 mm, but will be 6.5–7 mm. Freshwater pearls, Tahitian pearls, and South Sea pearls all measure to a full millimeter when considered uniform.
A graduated strand of pearls most often has at least 3 mm of differentiation from the ends to the center of the necklace. Popularized in theUnited Statesduring the 1950s by theGIsbringing strands of cultured akoya pearls home fromJapan, a 3.5momme, 3 mm to 7 mm graduated strand was much more affordable than a uniform strand because most of the pearls were small.
Earrings and necklaces can also be classified on the grade of the color of the pearl: saltwater and freshwater pearls come in many different colors. While white, and more recently black, saltwater pearls are by far the most popular, other color tints can be found on pearls from the oceans. Pink, blue, champagne, green, and even purple saltwater pearls can be encountered, but to collect enough of these rare colors to form a complete string of the same size and same shade can take years.
The vast majority of inexpensive colored pearls have been subjected to some form of dye, often a fabric dye.  This dye will only tend to penetrate the first layer or two of nacre, but this is enough to impart vivid and sometimes garish color to otherwise white pearls.  Truly valuable pearls are never dyed, and this process is not believed to add and in most cases would only subtract from their market value.
TheHindutradition describes the sacred Nine Pearls which were first documented in theGaruda Purana, one of the books of the Hindu scriptures. Ayurveda contains references to pearl powder as a stimulant of digestion and to treat mental ailments. According to Marco Polo, the kings ofMalabarwore a necklace of 108 rubies and pearls which was given from one generation of kings to the next. The reason was that every king had to say 108 prayers every morning and every evening.At least until the beginning of the 20th century it was a Hindu custom to present a completely new, undrilled pearl and pierce it during the wedding ceremony.
The Pearl, which can be transliterated to "Moti", a type of "Mani" fromSanskrit, is also associated with many Hindu deities, the most famous being theKaustubhathatLord Vishnuwears on his chest.
The Hebrew word פְּנִינִים 'pearl(s)' appears in several places in the Hebrew Bible (Job 28:18; Proverbs 3:15; 8:11; 20:15; 31:10; Lamentations 4:7), although its etymology is unclear.
In aChristianNew Testamentparable(Matthew13:45–46),Jesuscompared theKingdom of Heavento a"pearl of great price". "Again, the kingdom of heaven is like unto a merchant man, seeking goodly (fine) pearls: Who, when he had found one pearl of great price, went and sold all that he had, and bought it."
The twelve gates of the New Jerusalem are reportedly each made of a single pearl inRevelation21:21, that is, thePearly Gates. "And the twelve gates were twelve pearls: every several gate was of one pearl: and the street of the city was pure gold, as it were transparent glass."
Holy things are compared to pearls inMatthew7:6: "Give not that which is holy unto the dogs, neither cast ye yourpearls before swine, lest they trample them under their feet, and turn again and rend you."
Pearls are also found in numerous references showing the wickedness and pride of a people, as inRevelation18:16. "And saying, Alas, alas, that great city, that was clothed in fine linen, in purple, and scarlet, and decked with gold, and precious stones, and pearls!"
TheQuranoften mentions that dwellers of paradise will be adorned with pearls:
22:23 God will admit those who believe and work righteous deeds, to Gardens beneath which rivers flow: they shall be adorned therein with bracelets of gold and pearls; and their garments there will be of silk.
35:33 Gardens of Eternity will they enter: therein will they be adorned with bracelets of gold, silver and pearls; and their garments there will be of silk.
52:24 And they will be waited on by their youthful servants like spotless pearls.
The metaphor of a pearl appears in the longerHymn of the Pearl, a poem respected for its high literary quality, and use of layered theological metaphor, found within one of the texts ofGnosticism.
ThePearl of Great Priceis a book of scripture inthe Church of Jesus Christ of Latter-day Saints(LDS Church) and some otherLatter Day Saintdenominations.
Pearlis aMiddle Englishreligious poem.