Natural, Cultured, Composite and Imitation Pearls – Terminology and Classification (nomenclature)
The terminology and classification (nomenclature) for pearls (5.118), cultured pearls (5.48), composites (5.42) and imitation pearls (5.84) are established with reference to commercial usage and are in conformity with the practices of the international natural, cultured and imitation pearl trade. The terminology and classifications (nomenclature) of natural, cultured and imitation pearls as set out herein shall be used by all traders participating as members of CIBJO member organizations within all member nations.
NOTE – CIBJO recognises that its standards are subject to government regulations in the respective jurisdiction of CIBJO members. ( price of natural pearls )
2. Normative references
The Diamond Book, CIBJO, International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones), the World Jewellery Confederation, S.S. Del Sempione KM.28 20017 RHO Milano, Italy. firstname.lastname@example.org. ( price of natural pearls )
The Gemstone Book, CIBJO (International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones), the World Jewellery Confederation, S.S. Del Sempione KM.28 20017 RHO Milano, Italy. email@example.com. ( price of natural pearls )
The Precious Metal Book, CIBJO (International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones), the World Jewellery Confederation, S.S. Del Sempione KM.28 20017 RHO Milano, Italy. firstname.lastname@example.org. ( price of natural pearls )
The Gemmological Laboratory Book, A Guide for the Management and Technical Operations of Gemmological Laboratories, CIBJO (International Confederation of Jewellery, Silverware, Diamonds, Pearls and Stones), the World Jewellery Confederation, S.S. Del Sempione KM.28 20017 RHO Milano, Italy. email@example.com
Convention on International Trade in Endangered Species of Wild Fauna and Flora, Appendices I, II and III valid from 22 May 2009. International Environment House • Chemin des Anémones • CH-1219 Châtelaine, Geneva, Switzerland, firstname.lastname@example.org.
( price of natural pearls )
3. Pearl Categories
The jewellery industry and trade shall recognize four categories of pearl:
(a) The rare natural pearls (5.118) that are produced naturally by various saltwater (bi-valve and univalve) and freshwater molluscs. Articles source: THE PEARL BOOK, Natural, Cultured, Composite & Imitation Pearls — Terminology & Classification (Including information on modifications), 2013-08-12, CIBJO/Pearl Commission. ( price of natural pearls ) For Questions and answer you can contact & chat with us on:
Pearls are products of living organisms and thus react strongly to acids and chemicals, including those in perfumes, soaps, and hairsprays. Because soaps and dish-washing detergents that contain bleaching agents may discolor pearls, it is particularly important that rings containing black pearls be removed before immersion of the hands in these solutions.
To avoid dehydration and cracking due to dryness, some members of the trade recommend rubbing pearls with a dab of a natural oil placed on a soft cloth; this will also enhance the pearl’s beauty and luster. Historically, sandalwood oil has been preferred for this purpose (C. Rosenthal, pers.
comm., 1989). (Detail info: Pearl Necklace Wholesale)
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Because pearls are not very hard-only 3.5 on the Mohs scale – they can be scratched fairly easily. In manufacturing, it is recommended that the jeweler not place the pearls in a design where they will rub against other gems or metal or will be in a position of tension with a metal, such as in a prong setting. In storing pearls, it is best to keep them separate from other jewelry and wipe them with a soft cloth after wear. (Detail info: Pearl Necklace Wholesale)
CONCLUSION by Pearl Necklace Wholesale
Polynesian cultured black pearls have been called the “rainbow gem of the 20th century” (Salomon and Roudnitslza, 1986). Indeed, the development of the black-pearl Industry in the 1960s has now made the worldwide distribution of natural color cultured Black pearls feasible. Without this technology, blaclz pearls would have remained the oddity they were for the first 70 years of this century. Technology has also given the major gemological and pearl-research laboratories the tools by which to separate natural-color blaclz pearls from most of their treated counterparts. (Detail info: Pearl Necklace Wholesale)
Today, cultured blaclz pearls are seen in fine jewelry stores everywhere. Given the level of government support and the broad scope of the pearl-culturing industry in French Polynesia, it appears that there will continue to be a steady supply of these attractive gems in the future. (Detail info: Pearl Necklace Wholesale)
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Currently culturing in Polynesia is carried out on privately owned pearl farms like the Rosenthals’ or on pearl cooperatives. While there are many farms that produce less than 200 pearls annually, 24 farms have an annual production of over 5,000 cultured pearls. The farms tend to be more successful than the cooperatives because of the financial resources with which they are backed.
The cooperatives were established in 1971 by the Fisheries with loans from the Societe de Credit d Oceanie (SOCREDO) so that each atoll would have its own pearl-culturing industry. In 1988, there were approximately 40 cooperatives with 1,145 members. These cooperatives were reorganized in 1989 into 157 smaller family groups in an effort to improve production [M. Coeroli, pers. comm., 1989).
The cultured pearls are sold either through private sales or auctions. Most of the material produced on the farms is sold privately to pearl wholesalers and major jewelry companies. However, approximately 40% of the total production each year is sold at auction. Auctions are usually held once a year, in October. They are coordinated by EVAAM and GIE Poe Rava Nui, the two government agencies that oversee the pearl-culturing cooperatives (M. Coeroli, pers. comm,, 19891. These pearl auctions give the cooperatives the opportunity to help repay their government loans. They have also been important in making the international public and jewelry community more aware of Polynesian cultured black pearls.
The auctions are held in private, by invitation only, in Papeete, Tahiti. At the 1988 auction, 107 participants (co-ops and independent farms) presented their goods to an invited audience. The pearls were divided into lots of different pearl sizes and quantities. After examining the various pearls in a lot, buyers make specific offers for the particular lots in which they are interested. At the 1988 sale, approximately 70 lots were offered, with total sales exceeding $2 million (almost 10 times the total amount exported the first year the auction was held, 1981). In addition, 515 kg of “lzeshi” pearls, a by-product of culturing (figure 21), were sold (Cazassus, 1989).
In 1984, the principal buyers at auction were:
U.S., 30%; and
Swiss, 30%; with
France and other countries, 10%.
By 1988, the market was such that 84% of the production sold at auction went to Japanese buyers, with the remainder sold primarily to Tahitian jewelers [Cazassus, 1989).
It is important to remember that natural-color cultured black pearls have been commercially available for less than 20 years. Production has risen rapidly during this period (table 1)) yet it appears that demand still exceeds supply. In Japan, in particular, demand increased sharply in the second half of 1988 and continues to rise [Chun, 1989)
The great popularity of black pearls today can be directly attributed to the marketing efforts of two large companies, Assael International and Golay Buchel Inc. ‘almost single-handedly popularized the natural color Tahitian black pearl” (Federman, 1987). In the 1960s, he worked with Jean-Claude Brouillet, owner of the S. Marutea Atoll, to develop a viable black-pearl culturing operation. Eventually, they produced as many as 22,000 cultured pearls per harvest. Backed by this production, in the early pearls directly to the jewelry industry, bypassing the traditional Japanese distribution system. Not only did he and Brouillet promote their pearls to tourists throughout French Polynesia, but they also wrote articles, placed advertisements in magazines around the world, and convinced major companies such as Harry Winston and Van Cleef and Arpels to include black cultured pearls in their inventories of fine jewels (figure 22).
Today, Assael continues to be a major force in the marketing of blaclz cultured pearls, along with other distributors
such as Golay Buchel, who plays the prominent role in the important Japanese market (A. Goetz, pers. comm., 1989).
Another key factor in raising the public’s awareness of black pearls has been the jewelry auctions held by Christie’s and Sotheby’s. In 1969, a three-row strand of 141 blaclz pearls sold for $168,000. Ever since, single pearls or pearl necklaces have been a routine item in the “magnificent jewelry” auctions. In October 1988, a double strand of blaclz and gray cultured pearls sold at Sotheby’s New York for $649,000 (figure 23). The threestrand necklace in figure 1 sold for $880,000 at Christie’s October 24, 1989, auction in New York.
Pearls are marketed in Tahiti through different jewelry stores, some owned by the pearl producers themselves. For example, the Tahiti Pearl Center and Museum in Papeete is owned by Robert Wan, currently the largest producer of blaclz cultured pearls. The museum not only sells pearl jewelry, but also educates through videos, photos, and displays. Most hotels display pearls and pearl jewelry, thus exposing travelers to the gem.
Articles source: POLYNESIAN BLACK PEARLS, By Marisa Goebel and Dona Mary Dirlam For Questions and answer you can contact & chat with us on:
Wholesale Pearl Necklaces : Modern Pearl Identification
In 1920, Rosenthal recommended a relatively simple method for identifying dyed pearls: “When a [natural] blaclz pearl is scraped, the powder is white, but in the case of an artificially colored pearl, the powder is black.” While this procedure is accurate for some dyed pearls, it is also destructive. Similarly successful experiments in the 1970s with a Vickers hardness machine- (komatsu and Alzamatsu, 1978) were never adapted for routine testing because of their destructive nature. Today, because of the sophisticated equipment and experience needed to identify treatment, definitive pearl testing requires the resources of a well-equipped gemological or pearltesting laboratory. ( source : Wholesale Pearl Necklaces )
Currently gemologists at most Western gemological laboratories commonly use long-wave U.V fluorescence, X-ray fluorescence, X-radiographs, visual observation, and microscopic examination to separate treated from natural- color pearls. These tests are often used in conjunction with other procedures to determine first whether the pearl is natural or cultured (figure 20). Our primary concern in the following discussion, however, is their application in separating natural-color from treated blaclz pearls. ( source : Wholesale Pearl Necklaces )
U.V fluorescence can be diagnostic in this separation. For example, the fluorescence of natural-color blaclz pearls commonly varies from bright red (pearls from Baja California) to dull reddish brown (Tahiti pearls) when exposed to long-wave U.V radiation, while dyed pearls are usually inert or fluoresce a dull green (Benson, 1960; Crowningshield, 1970; Fryer et al., 1987; R. Crowningshield, pers. comm., 1989). ( source : Wholesale Pearl Necklaces )
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X-ray fluorescence spectral analysis involves exposing the sample to X-rays and measuring the wavelengths emitted with a spectrometer (Komatsu and Alzamatsu, 1978). Silver used in the various silver salt treatments will be detected. This test must be performed carefully, by an experienced technician, since the sample pearls have been known to turn brown-black if exposed to the x-rays in a wave-length dispersive x-ray fluorescence unit. Therefore, most gem-testing laboratories use an energy-disersive XRF unit (as described in Liddicoat, 1987). ( source : Wholesale Pearl Necklaces )
X-radiography, a technique developed in the 1920s to separate natural from cultured pearls, has been discussed in detail in the standard gemology texts (see, e.g., Webster, 1983; Liddicoat, 1987). The method works on the principle that different materials such as nacre, conchiolin, and silver vary in their degree of transparency to X-radiation (Brown, 1979). Cultured pearls usually show high relief between the nucleus, with its dark ring of conchiolin, and the nacre. In a silver-treated pearl, the silver tends to concentrate in the area of the conchiolin. Because silver is opaque to X-rays, this area commonly appears white on the X-radiograph. ( source : Wholesale Pearl Necklaces )
The white ring or area around the nucleus of a treated blaclz pearl is sometimes called a reversal ring (Fryer et al., 1986, pp. 173 and 174). Also used in pearl identification is visual observation supplemented by microscopic observation. To the unaided eye, dyed materials will sometimes show an unusually even distribution of color throughout the pearl and in some cases throughout an entire strand of pearls. With magnification, dye can be seen concentrated around the drill hole and even extending out into the pearl in a vein-like fashion (as illustrated in Fryer et al., 1984, p. 230). ( source : Wholesale Pearl Necklaces )
In some instances, dye can be detected by using a cotton swab dipped in a weak (e.g., 2%) solution of nitric acid on an inconspicuous area of the pearl. This is, however, another destructive test (Fryer et al., 1984, p. 229). Visual examination is also useful in identifying irradiation in the smaller Alzoya pearls. Irradiation will darken freshwater pearls and shells, but not saltwater pearls. Therefore, since cultured pearls use freshwater-shell nuclei almost exclusively, the dark bead nucleus of an irradiated pearl is easily seen through the drill hole of the pearl. ( source : Wholesale Pearl Necklaces )
The color of the nacre is unchanged (Fryer et al., 1986, p. 173, and 1988, p. 244, figure 11). One must be careful, however, to make several tests on each pearl, since while irradiation changes the color of the bead, it does not change the reaction of the pearl to long-wave U.V. radiation (Matsuda and Miyoshi, 1988). Even undrilled pearls can provide clues to the experienced pearl scientist by virtue of their visual appearance. The intense color and metallic luster
have been cited as indications of treatment (see, e.g., Fryer et al., 1985). ( source : Wholesale Pearl Necklaces )
It should be noted that size can be another important indicator of treatment. Small, rounded pearls 8 mm or less with very blaclz, gray, green, or blue-green hues are generally treated pearls – that is, smaller Alzoya pearls that have been dyed or irradiated-since the pearls grown in P. marguritifera are seldom smaller than 9 mm. Again, though, it is important to test pearls carefully, because some localities such as Baja California produce a lustrous blaclz pearl of natural color in small sizes. Black iilzeshi” pearls can also occur in small sizes. ( source : Wholesale Pearl Necklaces )
In recent years, Japanese scientists have led the way in pearl research. In 1978, Komatsu and Alzamatsu reported the success of their experiments with infrared film to separate natural-color from dyed blaclz pearls. Alzamatsu (pers. comm., 1989) reports that the Milzimoto Research Laboratory now finds spectrometry to be an even more efficient method to make the separation between natural-color and silver-treated blacks. Pearls from Pinctada margaritifera have a specific absorption at 700 nm that is caused by the blaclz pigment and can be easily measured by a spectrophotometer. ( source : Wholesale Pearl Necklaces )
The team of T Miyoshi, Y. Matsuda, and H. Komatsu has focused on methods for determining the parentage of cultured pearls using laser-induced fluorescence measured by a spectrofluorophotometer. In their 1987 paper, they
reported their observation of two fluorescence peaks-at 450 nm and 620 nm-in l? margarjtjfera. The 620 peak was not observed in P. maxima or P. fucata martensi, because the shells of these oysters do not contain porphyrins. This
makes it possible to separate l? margaritifera pearls from those produced by these two subgroups. Research such as this will provide the basis for more definitive pearl testing in the future. ( source : Wholesale Pearl Necklaces )
Articles source: POLYNESIAN BLACK PEARLS, By Marisa Goebel and Dona Mary Dirlam ( source : Wholesale Pearl Necklaces ) For Questions and answer you can contact & chat with us on:
As discussed above, color in pearls is a mixture of body color and overtones. The body color is determined by a combination of factors, including the biology of the molluslz (specifically the mantle tissue), the composition of the mother-of-pearl shell, and trace elements present in the water environment. Japanese researchers have investigated the body color in pearls extensively for over 50 years (Fox, 1979). They cite the presence of porphyrins (a group of water-soluble, nitrogenous 16-member ring organic compounds) in the shell of the molluslz as a primary cause of color in colored oyster pearls.
In inolluslzs, the porphyrins combine with metals such as lead and zinc to form metalloporphyrins. These same porphyrins produce a red fluorescence that is useful in identifying natural color in blaclz cultured pearls. Miyoshi et al. (1987) illustrate the diagnostic spectra produced by porphyrins present in the nacre. Also contributing to the color of most blaclz pearls is the presence of brownish organic substances that exist between the translucent porphyrin- containing nacre and the bead nucleus (Miyoshi et al., 1987; l? Galenon, pers. comm., 1989). This substance is thought to be conchiolin, but research to date has not been conclusive. Fritsch and Rossman (1988) describe the cause of the “high order” interference colors -overtone and orient -seen in black pearls as “light passing through and reflected back by alternating layers of aragonite [in the nacre] and conchiolin.” The finer the layers of nacre are, the more orient a pearl has (R. Wan, pers. comm., 1989).
In a 1971 article, C. Denis George lamented his unsuccessful search for even one natural-color black pearl in visits to Mexico City, New York, and Paris. He was routinely offered treated blaclz pearls that were represented to be natural color, and he railed against the “unscrupulous suppliers” who were perpetrating this “miserable and fraudulent” situation. In fact, from 1900 to 1978 (when cultured black pearls first began to appear in quantity), there were far more treated than natural-color black pearls on the market. One result of the overharvesting of I? margaritifera in the 19th century was that by 1900 there was a shortage of natural-color blaclz pearls. To fill this void, people began to use silver nitrate solutions to dye the smaller Alzoya pearls common to Japan (figure 19).
Even today, silver nitrate and other silver salts are probably the most common form of treatment to turn white and off-color Akoya pearls black (Komatsu and Alzamatsu, 1978; Taburiaux, 1985). Although pearl treaters are among the most secretive in the gem industry, we do know that the basic procedure involves soaking the pearls in a weak solution of silver nitrate and dilute ammonia and then exposing them to light or hydrogen sulfide gas. This produces a change of color in the conchioliii that makes the pearl appear black in reflected light. The resulting color is stable to light and heat (Nassau, 1984). Because the hues of brown-black, green-black, and blaclz are similar to natural colors, it is virtually impossible to distinguish them by visual observation alone (Taburiaux, 1985).
Another, reportedly organic, dyeing technique was commonly practiced from approximately 1915 through the 1920s. Called the French Method, it was used by a few treaters in Paris on off-color natural pearls. Although little is recorded about the actual procedure, we do know that it can be detected with a microscope when dye concentrations are present. Pearls were shipped from Japan to Paris for treatment and then back to Japan for sale (R. Crowningshield, pers. comm., 1989). In 1920, Rosenthal cautioned jewelers to be aware of pearls treated by this process. Although historically treatment has involved Akoya cultured pearls, it was inevitable that attempts would be made to enhance light-color P. maxima and P. margaritifera cultured pearls as well. In 1987, Fryer et al. reported seeing a strand of 11- to 14-mm blaclz cultured pearls that showed evidence of silver nitrate dye. More recently, in September 1989, the GIA Gem Trade Laboratory in New York examined two 12-mm blaclz cultured pearls that showed evidence that they might have been dyed.
The laboratory staff subsequently received confirmation from the trade that some South Sea pearls were being treated to darken the color (D. Hargett, pers. comm., 1989). One of the more recent treatments used on P, fucata martensii (Alzoyas) in an effort to darken mediocre-color cultured pearls is irradiation, specifically with a cobalt gamma source. According to Matsuda and Miyoshi (1988), gamma-ray irradiation can change off-color cultured Alzoya pearls to an attractive bluish gray. These authors report that irradiation of Alzoya pearls began in the 1950s with the ‘Atoms-for-Peace Program” and resulted in irradiated cultured pearls first appearing on the market in the 1960s. Ken Tang Chow’s patent on irradiating pearls, filed in 1960 and granted in 1963, sheds some light on the procedure used. The technique he patented involves exposure of the pearl to cobalt-60 with an intensity of 1,000 curies of gamma rays at a distance of 1 cm from the source for about 20 minutes at room temperature. Chow found that longer periods of irradiation did not produce any appreciable change in color. He also reported that the irradiated pearls were stable to light and heat.
Scientists have often noted that the color of freshwater shells and pearls can be changed by irradiation more easily than that of saltwater oysters. They attribute this to a change of manganese compounds (MnC03+MnO) which are more abundant in freshwater mollusks (Wada, 1981). Irradiating Alzoyas produces a darkening of color because the freshwater bead nucleus darkens and influences the body color. In P. margaritifera, the much thicker nacre would not allow the color shift of the nucleus to be visible (R. Crowningshield and D. Hargett, pers. comm., 1989).
Dr. George Rossman, of the California Institute of Technology, recently experimented with the irradiation of three Polynesian blaclz pearls following the procedure outlined in Chow’s patent, but left them in the reactor for slightly longer than 24 hours. No appreciable change was observed in these pearls compared to their control samples, although a color shift was observed in the freshwater pearls irradiated at the same time (pers. comm., 1989).
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