Natural Pearls vs. Cultured Pearls Natural pearls, are pearls formed by chance. The shape, size, and quality of natural pearls vary widely. Cultured pearls have been given a helping hand by man and are consistent in shape, size and quality. Cultured pearls can also be mass produced. Naturally occurring pearls develop when an irritant, usually a parasite, accidentally finds its way into a pearl oyster or other mollusc. The mollusc reacts by coating the irritant with layer upon layer of a substance known as ‘nacre’. Nacre is an organic secretion that gives the pearl its iridescent beauty. This unique relationship gives birth to the natural pearl.
Cultured pearls are created by inserting a foreign object into a saltwater oyster or freshwater mollusc. The same process of natural pearl creation then takes place. Cultured pearls can only be distinguished from natural pearls through the use of x-rays, which reveals the nucleus of the pearl. Today, nearly all pearls are cultured.
The History of Pearl Culturing The cultured pearl was developed to guarantee a steady supply of pearls and to satisfy the ever increasing demands of the consumer. Modern-day cultured pearls are the result of discoveries made in the late 19th and early 20th centuries, by Japanese researchers Tatsuhei Mise, Tokishi Nishikawa, and Kokichi Mikimoto. Early in Mikimoto’s career he focused on saltwater mabé pearl production. He eventually perfected his technique for producing round cultured saltwater pearls. This technique involved inserting tissue into the gonad of an Akoya mollusc. He patented this technique in 1916.
Mikimoto’s technique revolutionized the pearl industry by allowing consistent production of a large number of pearls. High quality, round pearls could now be produced by the millions; making them available and affordable to everyone. Today, the cultured pearl industry has essentially replaced the natural pearl industry with production of cultured freshwater pearls and cultured saltwater pearls including South Sea, Tahitian, and of course Mikimoto’s original Akoya pearls. By the 1980’s the Chinese had entered the free-market and the demand for Chinese pearls exploded. Today China is the predominant commercial producer of freshwater pearls on pearl farms.
Today cultured pearls are grown by the thousands on pearl farms. The first step in the process is to obtain the molluscs that will be nucleated. The original practice was to simply collect the molluscs from their natural habitat. Today many pearl farms have an extensive breeding program. After fertilization and the initial growth period baby molluscs are moved to a “nursery” bed and tended for 1 to 2 years until they are large enough to be nucleated.
Thousands of molluscs are nucleated and then cultivated for 2-5 years, the time required for a pearl to develop. Saltwater pearls are nucleated using a “bead” made of mother-of-pearl. This bead is covered with a piece of donor oyster tissue and implanted in the oyster’s reproductive organ called the gonad. The pearl will develop in the shape of the “bead” that was implanted. The result of this process is very uniform pearls.
Freshwater pearls are grafted with mantle tissue only. The implants are placed in the valves rather than in the gonad of the mussel. Each mussel can accept 12 to 16 grafts per valve and will produce 24 to 32 pearls per culturing cycle. After the pearls have been nucleated they are returned to the beds to grow for several additional years.
Once the pearls are fully developed, they are harvested. The shell and meat of the saltwater Akoya and freshwater mussel are discarded after harvesting. South Sea and Tahitian oysters are carefully hand harvested. For each fully developed pearl that is removed a new nucleus is implanted in the already formed pearl sac. The oysters are then returned to the bed to grow another pearl. These particular oysters can be recultivated several times during their life cycle. After the pearls are harvested they are washed and sorted. Some pearls are then bleached, heat-treated or dyed.
Like other farming, pearl farming depends as much on luck as on skill. A pearl farm can be devastated by water pollution, storms, excessive heat or cold, disease and other natural and man-made factors. In recent years Chinese pearl farms have been impacted negatively by severe storms, pollution and over production. This will lead to a decrease in availability and an increase in price of freshwater pearls.
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Glass pearl beads wholesale : Shells & Type of Pearls
For thousands of years, human beings have adorned themselves with shells. Many cultures of the world have believed that delicate shell shapes bring fertility, good fortune and safe travel. In today’s urban world, shells represent the essence of summer with their organic, curving forms reminding us of ocean waves and sandy beaches. Many shells have natural perforations and can simply be strung the way they are, while others require modification to enhance their best features and to make them wearable. Shells with iridescent inner layers are often ground into thin veneers and used for mosaic-like inlay, while thick shells are often carved with cameos or patterns. Most shells are porous and accept dyes and varnishes well, which can enhance their natural beauty. (refference: glass pearl beads wholesale )
Creatures called molluscs produce shells to protect their soft invertebrate bodies. The mollusc group is very diverse, with over 100,000 species alive today. Molluscs that produce wearable shells include univalves: those with a single shell, like snails, and bivalves: those with a hinged shell like clams, mussels, scallops and oysters. All molluscs have specialized organ tissue called mantle, which secretes calcium carbonate to produce the protective shell. The inner lining of the shell is especially smooth to protect the delicate invertebrate body from irritation. (refference: glass pearl beads wholesale )
The most popular univalve shells used for personal adornment include cowry, abalone, cones, turbo, olive and everlasting shell. Cowry shells are especially well known as they can be found all over the world. These naturally glossy shells come in many colours; one familiar variation is a speckled brown on creamy white. A cowry shell starts out looking like a traditional snail shell and develops into its unique shape as the mollusc matures. These shells are often drilled and strung whole or the backs of the shells are sliced off so the beads will lie flat. Since they were portable, durable and difficult to replicate, cowry shells were used as currency by ancient Chinese, Indian and African cultures. (refference: glass pearl beads wholesale )
Another popular univalve shell used for personal adornment is abalone. The scientific name for abalone, “Haliotis” means “ear of the sea” and refers to the flattened shape of the shell. The rough outer portion of the abalone is ground down to reveal the stunning inner layers of the shell. The nacreous inner surface is a silvery blue-green that sometimes contains swirls of pink, orange and lavender. The most vibrantly coloured species of abalone is called “paua” and comes from the waters around New Zealand. (refference: glass pearl beads wholesale )
Other bivalve mollusc shells used for personal adornment include species of mussel and clam. Many mussels and clams have brightly coloured shells and are simply drilled and worn. One famous bivalve mollusc is the “quahog clam” that’s white and purple shell are carved into Wampum by North-eastern Native Americans. (refference: glass pearl beads wholesale )
The most popular part of many bivalve shells is “mother-of-pearl”- the nacreous inner lining. As the mollusc matures, the inner surface of the shell becomes coated with iridescent or pearly-coloured nacre, the same material that forms pearls. The rough, plain outer coating of the shell is ground down or cut off, leaving only the luminescent inner layer. Thick layers of mother-of-pearl may be formed into beads, while thinner layers are cut into small pieces and fitted into mosaic beads and pendants. Some mother-of-pearl comes from marine pearl-bearing oysters such as Silver Lip, Black Lip or Gold Lip, but the vast majority comes from freshwater pearl-bearing mussels. (refference: glass pearl beads wholesale )
Types of Pearls
Virtually every pearl on the market today is a cultured pearl, grown in either a range of molluscs including salt-water oysters and freshwater mussels. The following is interesting information on each type of cultured pearl on the market today. There are three types of salt-water or marine cultured pearls; South Sea Pearls, Tahitian Pearls and Akoya Pearls. Marine culturing involves seeding a marine oyster’s reproductive organ with a bead nucleus and a small piece of mantle tissue. Marine pearls are left to grown for several years before the pearls are harvested. The majority of pearls used for beading today are cultured freshwater pearls. Freshwater pearls are grown in freshwater mussels and are seeded with the fleshy mantle tissue of a donor mussel. Each mussel is seeded with 12 to 16 insertions per valve resulting in 24 to 32 pearls per mussels after being left to grow for 2 to 6 years. Since freshwater pearls are not seeded with a bead nucleus these pearls are rarely perfectly round. (refference: glass pearl beads wholesale )
Salt-Water Pearls South Sea Pearls There are two groups of South Sea cultured pearls: white and black. Pearls from the white group are primarily cultured in the waters of northern Australia, the Philippines and Indonesia. Their colours range from gold or light-yellow; varieties primarily from the Philippine and Indonesian waters and white or silvery hues; varieties that occur mainly in Australian waters. Pearls from the black group, including the legendary black pearl of the South Pacific, are found over a wide area from the Cook Islands to the Gambier Islands in French Polynesia. (refference: glass pearl beads wholesale )
Tahitian Pearls Tahitian Pearls are some of the most beautiful and most unique pearls in the world. They produced by the black-lipped oyster around Tahiti and the French Polynesian Islands. There are no actual pearl farms on Tahiti but many are found in the islands of French Polynesia. The oyster itself is quite large, as much as 12 inches across and up to 10 pounds, which results in larger than average pearls. Tahitian Pearls are unique for their naturally dark colours from charcoal to dark green blacks. (refference: glass pearl beads wholesale )
Akoya Pearls Considered to be the classic cultured pearl, Akoya Pearls are cultured in south-western Japan and China. The Akoya oyster is the smallest pearl-producing oyster used in pearl culturing. The resulting pearls also tend to be smaller, ranging in size from 2mm to 11mm and are consistently round or nearly round making them extremely desirable. Akoya Pearls are known for their lustre and their soft pinkish white to creamy silver colours. Chinese Akoya pearl farming has surpassed Japanese production and now rivals Japanese Akoya pearls in quality and quantity. (refference: glass pearl beads wholesale )
Freshwater Pearls Freshwater Pearls Freshwater pearls come from molluscs that live in the fresh waters of ponds, lakes and rivers. China, the world leader in freshwater pearl production has been involved with freshwater pearl harvesting since the 13th century. Recently over-harvesting and pollution in China has reduced the number of pearl farming mussels. The availability of good quality and affordable freshwater pearls has been impacted by this environmental disaster. Freshwater pearls come in an astonishing array of sizes, shapes, and colours. (refference: glass pearl beads wholesale )
Biwa Pearls are small, uniquely shaped cultured pearls from the freshwater mussels of Lake Biwa in Japan. They were first produced in the 1930’s and at that time the quality of the Biwa Pearl rivalled both natural and cultured saltwater pearls. For many years any freshwater pearl was called a “Biwa” regardless of where it came from. Today this name is often used to describe cultured freshwater pearls of this shape. Other Types of Pearls Keishi Pearls Keishi pearls form when the mollusc rejects and spits out the implanted nucleus before the culturing process is complete. Keishi pearls form in either saltwater or freshwater pearls. Sometimes the implanted tissue breaks up and a separate pearl sac forms without a nuclei. These small freeform pearls are solid nacre and range in colour from silvery white to silvery grey. They are generally small in size and, because they do not have a nucleus to shape the pearl, the resulting shapes vary widely. (refference: glass pearl beads wholesale )
Mabé Pearl or Blister Pearl The Mabé Pearl was named after the mabé pearl oyster which is found in the seas of Southeast Asia and in the Japanese islands around Okinawa. These “half pearls” grow against the wall of the oyster’s shell rather than in the tissue and are also called blister pearls. Once the pearl is fully developed the Mabé is made by cutting the blister from the shell, removing the nucleus, filling the pearl with resin and finishing the back with a piece of mother-of-pearl. Mabé Pearls are used for setting rather than stringing and are much less expensive than other cultured pearls. (refference: glass pearl beads wholesale )
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Pearls in history & wholesale jewelry making supplies
The earliest times people have been enchanted by pearls and the shells of the mollusks that produce them. Pearls are the oldest known gem, and have, for centuries been considered one of the most valuable. In many cultures, pearls were worn as a declaration of wealth and power, and used as talismans to bring good fortune, to ward off evil spirits and to cure illnesses. Ancient kings gave pearls as gifts and were buried with them as a symbol of their status, while their serfs paid taxes, settled debts and bartered with them. The pearl has long been associated with “charity” and the hope of a pearl after death was an incentive for living a good life. – tags : wholesale jewelry making supplies
Pearls were symbolic of purity, chastity and feminine charm. The pearl has been considered a symbol of unblemished perfection in many cultures. Pearls symbolize purity and innocence and are often associated with weddings for this reason. In the Hindu religion, the presentation of an un-drilled pearl and its piercing has formed part of the marriage ceremony. – tags : wholesale jewelry making supplies
Pearls, unlike other gems, are the product of living beings. Molluscs found in the lakes, rivers, and oceans of the world all naturally produce “pearls”. Some produce unattractive lumps while others yield the stunning spheres man has coveted throughout history. A natural pearl is formed when a small irritant (rarely a grain of sand) lodges in the mantle tissue of a mollusc. In response, the mollusc secretes a substance called nacre, and a pearl begins to be created. Nacre is a combination of crystalline and organic substances. The nacre builds up around the irritant in layers to protect the mollusc. After a few years, this build up of nacre forms the pearl. Most natural pearls only produce one pearl at a time while cultured pearls are “nucleated” to produce multiple pearls in each mollusc. – tags : wholesale jewelry making supplies
As early as 3500 BC, pearls were worn in civilized Middle Eastern and Asian societies. In fact, the oldest surviving pearl necklace was found in the sarcophagus of a Persian Princess. Pearls continued to grow in popularity through Roman times. In classical Rome, only free persons above a certain rank were allowed to wear pearl Jewelry. It is thought that a single pearl earring paid for one Roman general’s political campaign and that Julius Caesar may have invaded Britain in 55 B.C. to obtain freshwater pearls. After the fall of Rome, Constantinople became the centre of wealth and the centre of pearl trade because of its strategic position between the source and the consumer. – tags : wholesale jewelry making supplies
In the thirteenth and fourteenth centuries, pearls were still very fashionable in Europe as embellishments for clothing and as personal ornaments. During this period the Church was all-powerful and most European countries had implemented Sumptuary Laws in an effort to do away with the extravagance of the time. These laws prohibited people of lower incomes and lower estates to wear certain things. These laws even dictated who could wear pearls. For example, teachers and lawyers could not wear fringes or chains with pearls. – tags : wholesale jewelry making supplies
By the early 1700s the demand for pearls declined because the discovery of diamonds in Brazil made diamonds more affordable. Pearl supplies became inconsistent, and pearl imitations began to appear on the market. The late 1700s saw a reversal in fortune. Good harvests from several established pearl sources and the discovery of new sources gave the pearl industry a much-needed boost. The desire for pearls eventually resulted in demand exceeding supply. The early 1900s saw trade affected by a supply shortage and the appearance of cultured pearls on the market. Cultured pearls were not accepted immediately; it took several years for consumers and the industry to accept this new kind of pearl. Entrepreneurs intervened by stimulating pearl production with a process called culturing. – tags : wholesale jewelry making supplies
GUIDE to the world of PEARLS – south sea pearl earrings
The pearl is one of the ocean’s rarest treasures. Since ancient times natural pearls have been used as jewellery and ornaments and the oldest known pearl necklace is more than 4000 years old. Pearls were often regarded as having a mystical quality and a life of their own because of their unique glow that seems to radiate from their very centre. In Roman times women would take pearls to bed in the belief that they would assist them to have pleasant dreams (Refference: south sea pearl earrings).
SO WHAT EXACTLY IS A NATURAL PEARL?
It is an accident of nature. A natural pearl is produced when a minute foreign object, perhaps a tiny living sea creature, becomes stuck inside the shell and tissue of an oyster. When the oyster cannot get rid of the ‘irritant’ it
eases the discomfort by coating it in ‘nacre’. Nacre is made up of microscopic crystals; each crystal perfectly aligned with the others so that it reflects light to produce a glow of light and colour. The pearl is built up of layer upon layer of nacre. The more layers, the more lustrous the pearl. However, because natural pearls are so rare, they are expensive which is why ‘Cultured Pearls’ are a more affordable option (Refference: south sea pearl earrings).
CULTURED PEARLS – GIVING NATURE A HELPING HAND
Most pearls sold today are cultured pearls. These are pearls that are made the same way as natural pearls in
so far as an oyster coats an ‘irritant’ with nacre. However the ‘irritant’ does not find its way inside the oyster by accident. It is implanted by technologists who then supervise the process so that the oyster produces the best pearl possible by ensuring it has the food it requires and that the water temperature remains constant and free of pollutants. Because there are a larger number of cultured pearls available than natural pearls, it is easier to match pearls that are much the same size and shape. So a necklace of cultured pearls will be more even in shape and colour than one made up of natural pearls.
IMITATION PEARLS ARE EXACTLY THAT
They are not real pearls. Both natural and cultured pearls are produced by an oyster, however imitation pearls are man made. A round glass or plastic bead is simply coated in a pearly substance – lacquered and wax filled to produce an instant imitation pearl. The best way to tell if a pearl is imitation or not is to place it directly alongside a real one and compare the lustre. The real pearl will have a depth of lustre that the imitation cannot match. An imitation pearl generally will have a surface shine but no inner glow. Also look in the shaded area, in the real pearl you will see a clearly defined reflection, in the imitation pearl you won’t. An easy way to test whether a pearl is an imitation or cultured pearl is to feel the difference. But not with your fingers, with your teeth. The ‘tooth test’ is a reliable way to separate real pearls from the imitators. Simply run the pearl gently along the edge of your upper teeth. If it is a real pearl it will have a slightly gritty or sandy feel whereas an imitation pearl will slide smoothly along (Refference: south sea pearl earrings).
YOUR GUIDE TO THE PERFECT PEARL
Whether a pearl is natural or cultured, there are five factors that need to be looked at to determine its quality.
LUSTRE AND ORIENT
A pearl’s ability to reflect and refract light (lustre) creates an underlying play of colours within the pearl (orient) which gives a pearl its unique inner glow. The higher the lustre and orient the finer the pearl. To judge the lustre and orient look at the shadow area of the pearl not its shiny surface. (Refference: south sea pearl earrings).
Colour is another important factor when determining value. There are two elements when considering colour: body colour and overtone. The ‘body colour’ refers to the basic colour; white, yellow or black. The ‘overtone’ refers to the slight tint that may be present. Very white pearls with a rose-coloured tint are the rarest and most expensive. The creamier the colour becomes the less costly they are. Cultured pearls are available in many colours including gray, black, pink, blue and gold. (Refference: south sea pearl earrings).
How clean a pearl is depends on how free it is from surface imperfections. Small blisters, spots and cracks can all diminish a pearl’s worth. The cleaner the surface, the better. (Refference: south sea pearl earrings).
The more symmetrical the shape, the more valuable the pearl. Perfectly round pearls are extremely rare however nicely proportioned round, oval and tear shaped pearls are all highly valued. Irregularly shaped (baroque) pearls are less costly but their unusual shape can make for quite a dramatic look. (Refference: south sea pearl earrings).
As it is more difficult for oysters to grow large pearls, large pearls are more scarce and therefore more expensive. However two pearls of the same size may be valued differently because one may have a higher degree of lustre and orient than the other. (Refference: south sea pearl earrings).
TYPES OF PEARLS
AKOYA : Grown in pearl oysters off the coast of Japan and are one of the most familiar types of cultured pearls. They have a lovely orient and warm colour and rarely reach more than 9mm in size.
MABE : Large half-round cultured pearls that grow against the inside shells of oysters rather than within the body. Because of their hemispherical shape are less expensive than regular round cultured pearls. They are usually mounted in earrings, rings and brooches.
FRESH WATER : These are pearls that are cultivated in mussels rather than oysters and are found in fresh water lakes and rivers. Generally they have an elongated shape and a milky translucent appearance.
KESHI : Small, irregular shaped seedless pearls that form naturally in many cultured pearl oysters
SOUTH SEA PEARLS (AUSTRALIAN) : Rare and valuable large cultured pearls (10mm and larger) grown in the warm waters off the Australian coast. Found in a variety of colours including white, silver, gold, and rose.
SOUTH SEA PEARLS (INDONESIAN) : Large cultured pearls (8mm and larger) slightly smaller and creamier than their Australian counterparts.
TAHITIAN : Large gray to black cultured pearls (10mm and larger) with overtones of reds, blues and greens.
HOW TO CARE FOR YOUR PEARLS
Cultured pearls are precious gems and need to be treated as such:
When storing them in a purse or jewel box place them in a soft gem bag or wrap them in a silk cloth to protect them from being scratched by harder stones, metal edges or other jewellery.
Don’t wear pearls in the shower, in the swimming pool or while playing sport.
Put your pearls on after you have applied your cosmetics, hairspray and perfume.
To help prevent discolouration wipe them frequently with a damp, clean cloth.
Never clean pearls with a harsh detergent or jewellery cleaner. A drop of mild detergent in warm water should be all you need.
Restring pearl necklaces at least once every two years to keep your jewellery looking its best.
Any questions? Your Showcase Jeweller: Miss Joaquim Pearls is the expert to ask (Refference: south sea pearl earrings).
Tracing cultured pearls from farm to consumer: A review of potential methods and solutions
Abstract: This article reviews various methods that could be used to determine the geographic origin of cultured pearls, potentially allowing a consumer to trace them back to the farm. Chemical marking using different substances is possible due to the porosity of the nucleus and nacre. It is also possible to affi x a logo marker to the nucleus that can later be imaged using X-radiography. In addition, radio-frequency identifi cation chips are today so small that they can be housed within the nucleus of a cultured pearl. Also discussed is the potential of using trace-element chemistry to differentiate mollusc species and pearling regions. Carbon and oxygen isotopes could also be useful given that they reflect the waters in which a cultured pearl grew, and DNA testing may offer options in the future. (tags: wholesale pearl necklace )
Branded jewellery products are more successful than non-branded goods (Kapferer and Bastien, 2009). There is continued demand from jewellery consumers for branded goods and increasing desire for traceability of products (Conroy, 2007; Ganesan et al., 2009).(tags: wholesale pearl necklace ), Cultured pearls are an interesting case study where some products are branded (e.g., Figure 1), but traceability to source is something that is difficult to verify independently at present. A cultured pearl strand with a branded tag does not provide a clear guarantee of origin for the end consumer, given that individual cultured pearls can easily be exchanged or strands re-strung. At the same time, there is a growing interest in tracing cultured pearls through the supply chain, so that an end consumer knows which farm their cultured pearls came from.
Producers who operate responsibly are investigating ways of marking their cultured pearls so that provenance can be guaranteed to the end consumer. Any method used to trace cultured pearls must largely be invisible so as to maintain the commercial value of the end products. Cultured pearls are produced both with a nucleus (e.g., Akoya, South Sea and Tahitian) and without a nucleus (e.g., Chinese freshwater beadless products,(tags: wholesale pearl necklace ); for general reviews, see for example Gervis and Sims (1992) and Southgate and Lucas (2008). Different labelling/traceability approaches may be required for these two types of cultured pearls, based on their internal structure.
This article reviews a wide range of methods — chemical, physical and biological — that potentially could be used in tracing cultured pearls through the supply chain.
Pearls consist of fine polycrystalline calcium carbonate (CaCO3) crystals and traces of organic matter. The mother-of-pearl (also called nacre) surface of pearls is made up of aragonite tablets. A pearl’s porous structure means that it has a good potential for absorbing chemically doped or colour-doped solutions. A good example of this are dyed cultured pearls (e.g., Figure 2), which can be found in many different colours (Hänni, 2006; Strack, 2006).(tags: wholesale pearl necklace )
In a similar way, cultured pearls from selected producers could be marked using a colorless doped solution — that is unique to a pearl producer — after harvest. If chemically doped, these pearls could later be identified in a gemological laboratory using EDXRF spectroscopy (Hänni, 1981)(tags: wholesale pearl necklace ). However, the applicability of this approach is limited given that EDXRF spectroscopy is not in widespread use in the jewellery industry.
Alternatively, rather than marking the cultured pearl after harvest, one could mark the nucleus before insertion using a specific solution. However, if the nacreous overgrowth is too thick, it may not be possible to identify the chemical signal from the nucleus. Another approach would be to remove a tiny amount of nucleus material from a drilled cultured pearl for chemical analysis. (tags: wholesale pearl necklace )
The authors have experimented with the diffusion of fluoroamine (NH2F) into a cultured pearl, something a pearl farmer could easily do. The subsequent detection of fluorine could then be linked back to that farm. Fluorine is a relatively light element that is not detectable by EDXRF spectroscopy, but is best analyzed by nuclear magnetic resonance (NMR). However, NMR is cost-intensive and the instrument’s sample chamber is typically smaller than the diameter of a cultured pearl. (tags: wholesale pearl necklace )
If only a limited number of pearl farms are involved in such chemical marking of their cultured pearls, it could be viable to supply each of them with different cost-effective and nontoxic chemicals that could be detected in a gemological laboratory.
Labeling the nucleus or the surface of a cultured pearl Initial experiments using physical labels affixed to a cultured pearl nucleus were carried out in 2010 by author HAH. Thin (0.05 mm) rings consisting of gold wire were affixed to several Mississippi shell nuclei (the nucleus material commonly used in the pearl industry) and used to produce cultured pearls. The aim was to investigate the possible rejection of labelled nuclei by the molluscs and to see whether this gold label (or the associated adhesive) would infl uence cultured pearl growth. Results after six months showed that the labelling materials (gold and glue) had no infl uence on cultured pearl production and this spurred further efforts to investigate the production of nucleus logos. (tags: wholesale pearl necklace )
Any such logo marker must be extremely thin, be composed of noble metal (and therefore be resistant to corrosion) and have the same convex shape as the nucleus to ensure that the resulting cultured pearl is also round. However, the production of such round metal labels, generally 3–4 mm wide and 0.05 mm thick, is relatively expensive. Different label production techniques were tested, such as galvanic production, pressing, etching and cutting with a laser or water jets; these are widely used techniques in manufacturing (Schultze and Bressel, 2001). (tags: wholesale pearl necklace ). The water jet technique was most precise for cutting the contours of the logo, but still considered too expensive.
Several dozen logo tags (e.g., Figure 3) were affi xed to shell nuclei and sent to different marine farms to be tested in cultured pearl production. After the usual 12–18 month growth period, these ‘tagged’ cultured pearls were harvested and successfully examined with X-radiography (Figure 4). Due to the position of the logo in the peripheral part of a cultured pearl, there is only a statistically small chance of the logo being damaged during drilling. The production of such logo markers is relatively expensive, even if produced in large quantities. In addition, these cultured pearls need to be tested using X-rays, which is relatively unfeasible for a jeweller. (X-rays used for medical purposes, such as in dentistry, are not strong enough to visualize all required details within a cultured pearl of, e.g., 10 mm.) Nevertheless, for beaded cultured pearls that use a nucleus (e.g., Akoya, South Sea and Tahitian), this method is an option. For beadless cultured pearls (e.g., Chinese freshwater cultured pearls (tags: wholesale pearl necklace )), the introduction of a label together with the saibo (donor mantle tissue) would have the disadvantage of positioning the logo in the centre of the cultured pearl, resulting in a high likelihood of damage during the drilling process.
Another approach is to mark the surface of the cultured pearl rather than the nucleus. This could involve either laser engraving with a unique number (similar to laser inscriptions on diamonds) that can later be used to identify its source or embossing a hologram onto the surface of the cultured pearl that can be read with a suitable reader. Both of these methods are currently being investigated in French Polynesia (‘Redonner ses Lettres…’, 2013; ‘Le Tahiti Pearl Consortium Disparaît’, 2013) (tags: wholesale pearl necklace ). These methods are slightly destructive to a cultured pearl’s surface and it remains to be seen if they are acceptable to the pearl trade.
RFID – radio frequency identification Radio frequency identification (RFID) technology has undergone rapid development in the past decade and is now a widely used method in many technology applications (Want, 2006). It is increasingly being employed in jewellery management solutions (Wyld, 2010) (tags: wholesale pearl necklace ).
Through the miniaturization of RFID chips (transponders in millimetre sizes), the use of electromagnetic frequencies is a feasible option for the tagging/traceability of cultured pearls. Transponders are chips that contain relevant data which can be accessed with an RFID reader. These devices are inexpensive and they could be easily used in jewellery retail stores (‘June HK Fair Special…’, 2013)(tags: wholesale pearl necklace ) . Information stored on the chips could include the production location, harvest date and details about the pearl farm. Additional information can be added to the RFID chip after a cultured pearl has been harvested, including its quality grade, inventory data and unique identifi cation information that could be useful for theft recovery.
RFID chips have been introduced into commonly used Mississippi shell nuclei, which are currently being piloted by pearl farmers in the Pacific Ocean. One nucleus manufacturer (Fukui Shell Nucleus Factory, Hong Kong) has already brought to market nuclei that contain RFID chips (see ‘June HK Fair Special…’,2013)(tags: wholesale pearl necklace ) . Figure 5 shows such a ‘microchip embedded nucleus’ which, depending on its size, costs US$2–3 per piece. According to the manufacturer, these nuclei consist of two layers of shell material (i.e., laminated nuclei) and a 3 mm RFID chip that is located 1 mm below the surface of the nucleus (Figure 5). Figure 6 shows an X-ray shadow image of such chip embedded nuclei.
One disadvantage of these nuclei is the relatively high cost of the chips, which would be wasted in cultured pearls of low quality. Also, the 3 mm size of the straight-edged chips is rather large when taking into account that the nucleus has a spherical shape. The size and position of these chips within the nucleus means they may often be damaged during the cultured pearl drilling process. Rapid developments in RFID technology are promising, but we may need to await the further miniaturization of the chips before they become a feasible option for the cultured pearl industry. Advanced fingerprinting of pearl and shell materials Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) has become more widely used in the last few years in geosciences, even in gemmology (e.g., Saminpanya et al., 2003; Abduriyim and Kitawaki, 2006) (tags: wholesale pearl necklace ).
Many laboratories and researchers now employ it for the chemical characterization of gems because it has a low detection limit and can also detect light elements. With this method it is possible to carry out high-resolution spot analyses, which allows us to take into account possible chemical zoning in gem materials, including cultured pearls. The technique has been used for characterization of cultured freshwater pearls (Jacob et al., 2006) and natural saltwater pearls from Australian Pinctada maxima molluscs (Scarratt et al., 2012)(tags: wholesale pearl necklace ). To our knowledge, there are no published LA-ICP-MS data on a wider range of cultured pearls or shell samples from various mollusc species.
For this study, a preliminary LA-ICPMS investigation of cultured pearls and shell material was undertaken at the University of Bern. The instrumentation used a 193 nm ArF laser, and synthetic glass (SRM612) was used as a standard for calibration before and after each round of measurements. This was also done to ensure the reproducibility of measurements and detect possible impurities in the chamber that might affect subsequent data. The pits produced on the surface of the samples during ablation had a diameter of 160 μm. As such, the technique is quasi-nondestructive.
Table I lists the results for the seven shell samples and three cultured pearls from different locations that were analysed. It is clear that further research is required to compile a useful LA-ICPMS database that might permit origin determination of cultured pearls from different species. Another possible (and nondestructive) method for chemically finger printing gem materials is particle-induced X-ray emission (PIXE), which has been applied to ruby and emerald (Calligaro et al., 1999; Yu et al., 2000)(tags: wholesale pearl necklace ). More recently, PIXE was used on cultured pearls (Murao et al., 2013). Other studies have measured oxygen and carbon isotopic values of nacre and cultured pearls in an attempt to identify geographic origin (Yoshimura et al., 2010)(tags: wholesale pearl necklace ). However, all these techniques remain academic and expensive, and they presently do not fulfi l the requirements for a rapid and cost-effective tracing method for cultured pearls.
A final method that is very new but merits description is DNA finger printing of cultured pearls. Oyster shells and pearls have a biological origin and contain small amounts of organic matter between aragonite layers and in the form of organic pockets. A recently published study described how DNA can be extracted Figure 7: The Atlas Pearl farms that produced the necklace shown in Figure 1 are located in Bali (shown here) and West Papua, Indonesia. Giving consumers access to the origin of their cultured pearls may create additional value for pearl farmers. Photo by L. Cartier. from this organic material in cultured pearls in a practically nondestructive manner (Meyer et al., 2013)(tags: wholesale pearl necklace ).
The DNA can be used to identify the oyster species of the cultured pearl and the authors also proposed that geographic origin determination might also be possible using next generation sequencing (NGS) techniques in the near future. A similar approach has been used for geographic origin and species determination of ivory (Wasser et al., 2004)(tags: wholesale pearl necklace ).
The aim of this review is to show the range of currently available methods that potentially could be used to trace cultured pearls through the supply chain. Supply chain accountability and product traceability are becoming increasingly important issues in the jewellery industry. The branding strategies of various producers, wholesalers and jewellery companies would benefi t from additional support through an effi cient traceability method. Furthermore, there is a potential for responsible pearl farmers (e.g., Figure 7) to capture greater value for their products if they can be traced allthe way to the consumer, but the supply chain accountability and provenance need to be guaranteed (Conroy, 2005; Cartier 2012; Cartier and Ali, 2012)(tags: wholesale pearl necklace ).
As technology continues to evolve, the search for methods to trace cultured pearls through the supply chain should be addressed in collaboration with the gemmological community and the focus should be on developing cost-effective solutions that are feasible for those at all levels of the supply chain (producer, wholesaler, retailer and consumer)(tags: wholesale pearl necklace ).
Articles source: Henry A. Hänni and Laurent E. Cartier, The Journal of Gemmology / 2013 / Volume 33 / No. 7–8. (tags: wholesale pearl necklace )