Fascinating Fact About Pearls – Part 2

THE HISTORY OF PEARL HUNTING AND PEARL FARMING

 

PEARL HUNTING

 

• For thousands of years, most seawater pearls were retrieved by divers working in the Indian Ocean, in areas like the Persian Gulf, the Red Sea, and the Gulf of Mannar. Starting in the Han Dynasty (206 BC – 220 AD), the Chinese hunted extensively for seawater pearls in the South China Sea. In the 14^th century Arabian Sea, the traveller Ibn Battuta provided the earliest known description of pearl diving by means of attaching a cord to the divers waist.

 

CATCHING PEARLS – BERN PHYSIOLOGUS (IX CENTURY)

 

• When Spanish conquistadors arrived in the Western Hemisphere, they discovered that around the islands of Cubagua and Margarita, some 200km north of the Venezuelan coast, was an extensive pearl bed (a bed of pearl oysters). One discovered and named pearl, La Peregrina pearl, was offered to the Spanish Queen. According to Garcilasso de la Vega who says that he saw La Peregrina at Seville in 1507, (Garicilasso, “Historie des Incas, Rois du Perou,” Amsterdam, 1704, Vol, II, P.352) this was found at Panama in 1560 by a negro who was rewarded with his liberty, and his owner with the office of accolade of Panama.
• Margarita pearls are extremely difficult to find today and are known for their unique yellowish colour. The most famous Margarita necklace that anyone can see today is the one that the Venezuelan President Romulo Betancourt gave to Jacqueline Kennedy when she and her husband, Predient John F Kennedy paid an official visit to Venezuela.
• Before the beginning of the 20^th century, pearl hunting was the most common way of harvesting pearls. Divers manually pulled oysters from the ocean floors and river bottoms and checked them individually for pearls. Not all mussels and oysters produce pearls. In a haul of three tones, only three or four oysters will produce perfect pearls.

 

THE DEVELOPMENT OF PEARL FARMING

 

• Today, the cultured pearls on the market can be divided into two categories. The first category covers the beaded cultured pearls, including Akoya, SouthSea and Tahiti. These pearls are gonad grown, and there is usually one pearl 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 SouthSea and Tahitian, and 2-7 years for freshwater. This perliculture process was first developed by the British biologist Willian Saville-Kent who passed the information along to Tatsuhei Mise and Tokichi Nishikawa from Japan. The second category  includes the non-beaded freshwater cultured pearls and 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 do saturate the market completely. An impressive improvement of quality has taken place in the last ten years when the former rice grain shaped pebbles are compared with the near round pearls of today.
• The nucleus bead in a beaded cultured pearl is generally a polished sphere made from freshwater mollusc shell. Along with a small piece of mantle tissue from another mollusc (donor shell) to serve as a catalyst for the pearl sac, it is surgically implanted into the gonad (reproductive organ) of a saltwater mollusc. In freshwater periculture, only the piece of tissue is used in most cases, and is inserted into the fleshy mantle of the host mussel. SouthSea and Tahitian pearl oysters, also known as Pinctada maxima and pintada margaritifera, which survive the subsequent surgery to remove the finished pearl, are often implanted with a new, larger bead as part of the same procedure and then returned to the water for another 2-3 years of growth.

 

WHITE PEARL NECKLACE

 

• Despite the common misperception, Mikimoto did not discover the process of pearl culture. The accepted process of pearl culture was developed by the British Biologist William Saville-Kent in Australia and brought to Japan by Tokichi Nishikawa and Tatsuhei Mise. Nishikawa was granted the petent in 1916, and married the daughter of Mikimoto. Mikimoto was able 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 SouthSea pearl oyster in 1917 in the Phillipines, and later in Buton, and Palau. Mitsubishi was the first to produce a cultured SouthSea 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 6-8 cm in size, hence Akoya pearls larger than 10 mm in diameter are extremely rare and highly prized. Today, a hybrid mollusc is used in both Japan and China in the production of Akoya pearls. It is a cross between the original Japanese species, and the Chinese species Pinctada chemnitzii.

 

RECENT PEARL PRODUCTION

 

• China has recently overtaken Japan in Akoya pearl production. Japan has but ceased its production of Akoya pearls smaller than 8mm. Japan maintains its status as a pearl processing centre, however, and imports the majority of  Chinese Akoya pearl production. These pearls are then processed (often simply matched and sorted), relabelled as product of Japan, and exported.
• In the past couple of decades, cultured pearls have been produced using larger oysters in the South Pacific and Indian Ocean. The largest pearl oyster is the Pinctada maxima, which is roughly the size of a dinner plate. SouthSea pearls are characterised by there large size and warm lustre. Sizes up to 14mm in diameter are not uncommon. SouthSea pearls are primarily produced in Australia, Indonesia and the Phillipines.
• Mitsubishi commenced pearl culture with the SouthSea pearl oyster in 1916, as soon as the technology patent was commercialised. By 1931 this project was showing signs of success, but was ipset ny the death of Tatsuhei Mise. Although the project was recommenced after Tatsuhei’s death, the project was discontinued at theh beginning of WWII before significant production of pearls was achieved.
• After WWII, new SouthSea pearl projects were commenced in the early 1950’s in Burma and KuriBay and Port Essington in Australai. Japanese companies were involved in all projects using technicians from the original MitsubishiSouthSea pre-war projects.

 

FRESHWATER PEARL FARMING

 

• In 1914, pearl farmers began growing cultured freshwater pearls using the pearl mussels native to LakeBiwa. This lake, the largest and most ancient in Japan, lies near the city of Kyoto. The extensive and successful use of the Biwa pearl mussel is reflected in the name Biwa Pearls, a phrase which was at the time nearly synonymous with freshwater pearls in general. Since the time of peak production in 1971, when Biwa pearl farms produced six tons of cultured pearls, poloution has caised the virtual extinction of the industry. Japanese pearl farmers recently cultured ahybrid pearl mussel – a cross between a Biwa pearl mussel and a closely related species from China, Hyriopsis cumingi, in LakeKasumigaura. This industry has also nearly ceased production due ton pollution.
• Japanese pearl producers also invested in producing cultured pearls with freshwater mussels in the region of Shanghai, China. China has since become the worlds largest producer of freshwater pearls, producing more than 1,500 metric tons a year (in addition to metric measurements, Japanese units of measurements such as the kan and momme are sometimes encountered in the pearl industry).
• Led by pearl pioneer John Latendresse and his wife Chessy, the United States began farming cultured freshwater pearls in the mid 1960’s. National Geographic Magazine 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.

 

PEARL IN JEWELLERY

 

• The value of the pearls in jewellery is determined by a combination of lustre, colour, size, lack of surface flaws and a symmetry that are appropriate for the type of pearl under consideration. Among those attributes, lustre is the most important differentiator of pearl quality according to jewellers.
• 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.

 

SHAPES

 

• Pearls come in eight basic shapes: round, semi-round, button, drop, pear, oval, baroque and circled. 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 flattened round pearls and can also make a necklace, but more often are used in single pendants or earrings where the back half of the pearl is covered, making it look like a larger, rounder pearl.
• Drop and pear shaped pearls are sometimes referred to as teardrop pearls and are most often seen in earrings, pendants, or as a centre 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 characterised by there concentric ridges, or rings, around the body of the pearl.
• In general, cultured pearls are less valuable than natural pearls, whereas imitation pearls almost have no value. One way that jewellers can determine whether a pearl is a cultured or natural is to have a gem lab perform an x-ray of the pearl. If the x-ray 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 pearls can often be confused for natural pearls which present homogenous 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.
• Some imitation pearls are simply made of mother-of-pearl, coral or conch shell, while others are made from glass and are coated with a solution containing fish scales called essence d’Orient. Although imitation pearls look the part, they do not have the same weight or smoothness as real pearls, and their lustre will also dim greatly.

 

 

COLOURS OF PEARL JEWELLERY

 

• Earrings and necklaces can also be classified on the grades of the colour of the pearl. While white, and more recently black, saltwater pearls are by far the most popular, other colour tints can be found on pearls from the oceans. Pink, blue, champagne, green, black and even purple saltwater pearls can be encountered, but to collect enough of these rare colours to form a complete string of the same size and same shade can take years.

 

 

 

Fascinating Facts About Pearls – Part 1

PEARLS

 

• A pearl is a hard object produced within the soft tissue (specifically the mantle) of a living shelled mollusc.
• Just like the shell of a mollusc, a pearl is made up of calcium carbonate in minute crystalline form which has been deposited in concentric layers.
• The ideal pearl is perfectly round and smooth, but many other shapes of pearl occur. The finest quality natural pearls have been highly valued as gemstones and objects of beauty for many centuries, and because of this, the word pearl has become a metaphor for something very rare, fine, admirable and valuable.
• The most valuable pearls occur spontaneously in the wild, but they are extremely rare.
• Cultured or farmed pearls from oysters make up the majority of those that are currently sold.
• Pearls from the sea are valued more highly than freshwater pearls.
• However, almost all species of shelled molluscs are capable of producing pearls of lesser shine or spherical shape.
• The English word pearl originated (via French perle) from the Latin word perla. Margaret means pearl in Greek (the English name Margaret originated from the Greek word for pearl).
• Almost any shelled mollusc can, by natural processes, produce some kind of “pearl” when an irritating microscopic object becomes trapped within the molluscs mantle folds, but the great majority of these “pearls” are not valued as gemstones. Nacreous pearls, the best known and most commericially significant pearls, are primarily produced by two groups of molluscan bivalves or clams. A nacreous pearl is made from layers of nacre, by the same living process as is used in the secretion of the mother of pearl which lines the shell.
• A “natural pearl” or “wild pearl” is one that forms without human intervention at all, in the wild, and is very rare. Many hundreds of pearl oysters or pearl mussels have to be gathered and opened, and thus killed, in order to find even one wild pearl, and for many centuries that was the only way pearls were obtained. This was the main reason why pearls fetched such extraordinary prices in the past. A cultured pearl is formed in a pearl farm, using human intervention as well as natural processes.
• One family of nacreous pearl bivalves – the pearl oyster – lives in the sea, while the other – a very different group of bivalves – lives in freshwater; these are the river mussels such as the freshwater pearl mussel. Saltwater pearls can grow in several species of marine pearl oysters in the family Pteriidae. Freshwater pearls can grow within certain (but by no means all) species of freshwater mussels in the order Unionida, the families Unionida and Margaritiferidae.
• The unique lustre of pearls depends upon on the reflection, refraction, and diffraction of light from the translucent layers. The thinner and more numerous the layers in the pearl, the finer the lustre. The iridescence that pearls display is caused by the overlapping successive layers which break up the light falling on the surface. In addition, pearls (especially freshwater cultured pearls) can be dyed yellow, green, blue, brown, pink, purple or black.

 

FRESHWATER & SALTWATER PEARLS

 

• Shell of one species of freshwater pearl mussel is called Margaritifera margaritifera.
• Freshwater and saltwater pearls may sometimes look quite similar, but they come from different sources.
• Natural freshwater pearls form in various species of freshwater mussels, family Unionidae, which live in lakes , rivers, ponds and other bodies of fresh water. These freshwater pearl mussels occur not only in hotter climates, but also in colder more temperate areas such as Scotland. However, most freshwater cultures pearls sold today come from China.
• Saltwater pearls grown within pearl oysters, family Pteriidae, which live in oceans. Saltwater pearl oysters are usually cultivated in protected lagoons or volcanic atolls.

 

CREATION OF A PEARL

 

 

• The difference between wild and cultured pearls focuses on whether the pearl was created spontaneously by nature – without human intervention – or with human aid. Pearls are formed inside the shell of certain molluscs as a defence mechanism against a potentially threatening irritant such as a parasite inside its shell, or an attack from outside, injuring the mantle tissue. The mollusc creates a pearl sac to seal off the irritation.
• The mantle of the mollusc deposits layers of calcium carbonate (CaCO3) in the form of the mineral aragonite or a mixture of aragonite and calcite (polymorphs with the same chemical formula, but different crystal structure) held together by an organic horn-like compound called conchiolin. The combination of aragonite and conchiolin is called nacre, which makes up mother-of-pearl.
• The commonly held belief that a grain of sand acts as an irritant is in fact rarely the case. Typical stimuli include organic material, parasites and even damage that displaced mantle tissue to another part of the molluscs’ 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, together or without a spherical bead (beaded or beadless cultured pearls).

 

NATURAL PEARLS

 

• Natural pearls are nearly 100% calcium carbonate and conchiolin. It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters the bivalve mollusc, and settles inside the shell. The mollusc, being irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant. The 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). The presence of columnar calcium carbonate rich in organic material indicates juvenile mantle tissue that formed during the early stages of pearl development.
• Displaced living cells with a well defined task may continue to perform their function in their new location, often resulting in a cyst. 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 their natural product: calcium carbonate. The pocket is called the pearl sac, and grows with time by cell division; in this way the pearl grows also. The juvenile mantle tissue cells, according to their stage of growth, produce columnar calcium carbonate, which is secreted from the inner surface of the pearl sac. With ongoing time the external mantle cells of the pearl sac proceed to the formation of tabular aragonite. When the transition to nacre secretion occurs, the brown pebble becomes covered with a nacreous coating. As this process progresses, the shell itself grows, and the pearl sac seems to travel into the shell. However it actually stays in its original relative position within the mantle tissue. After a couple of years, a pearl will have formed and the shell might be found by a lucky pearl fisher.

 

CULTURED PEARLS

 

• Cultured pearls are the response of the shell on a tissue implant. A tiny piece of mantle tissue of the donor shell is transplanted into a recipient shell. This graft will form a pearl sac and the tissue will precipitate calcium carbonate into this pocket. There are a number of options for producing cultured pearls: use freshwater or seawater shells, transplant the graft into the mantle or the gonad, add a spherical bead or do it non-beaded. The large majority of saltwater cultured pearls are grown with beads, the trade name of the cultured pearls are Akoya, white or golden South Sea, or black Tahiti. The majority of beads-less cultured pearls are mantle grown in freshwater shells, trade name, Chinese cultured pearls.
• Cultured pearls (bead-less or beaded) and imitation pearls can be distinguished from natural pearls by X-ray examination. Nucleated cultured pearls are often “pre-formed” as they tend to follow the shape of the of the implanted shell bead nucleus. Once the pre-formed beads are inserted into the oyster, it secretes a few layers of nacre around the outside surface of the implant before it is removed aster six months or more.
• When a cultured pearl is X-rayed, it reveals a different structure to that of a natural pearl. A beaded cultured pearl shows a solid centre with no concentric growth rings, whereas a natural pearl shows a series of concentric growth rings. A bead-less 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.

 

GEMOLOGICAL IDENTIFICATION

 

• A well equipped gem testing laboratory is able to distinguish natural pearls from cultured pearls by using  a gemological x-ray in order to examine the centre of a pearl. With an x-ray 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 and cultured pearls can be distinguished from imitation pearls using a microscope. 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.

 

VALUE OF A NATURAL PEARL

 

• Quality natural pearls are very rare jewels. The actual value of a pearl is determined in the same way as it would if it were any other precious gem. The valuation factors include size, shape, and quality of surface, orient and lustre.
• Single natural pearls are often sold as collectors items, or set as centre pieces in unique jewellery. Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars. (In 1917, jeweller Pierre Cartier purchased the Fifth Avenue mansion that is now the New York Cartier store for US$100 cash and a double strand of matched natural pearls valued at the time at US$1 million).
• Keshi pearls, although they often occur by chance, are not considered natural pearls. They are a by-product of the culturing process, and hence do not happen with out human intervention. These pearls are often quite small: typically a few millimetres in size. Keshi pearls are produced by many different types of marine mollusc and freshwater mollusc in China. Today, many Keshi pearls are actually intentional, with post harvest shells returned to the water to regenerate a pearl in the existing pearl sac.

 

ORIGIN OF A NATURAL PEARL

 

• Previously, natural pearls were found in many parts of the world. Present day natural pearling is confined mostly to seas off Bahrain. Australia also has one of the worlds 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.

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