Volume 28 / No. 8 / 2003
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t ThThe JournaJournaJournalll ooff ,••, emmoemmoemmoj Volume 28 No. 8 October 2003 «,-- .'-:S«fe* The Gemmolog Testini g Laboratoriation and Gem Testing Laboratory of Great Britain Gemmological Association and Gem Testing Laboratory of Great Britain 27 Greville Street, London EC1N 8TN Tel:+44 (0)20 7404 3334 Fax: +44(0)20 7404 8843 e-mail: [email protected] Website: www.gem-a.info President: Professor A.T. Collins Vice-Presidents: N. W. Deeks, A.E. Farn, R.A. Howie, D.G. Kent, R.K. Mitchell Honorary Fellows: Chen Zhonghui, R.A. Howie, K. Nassau Honorary Life Members: H. Bank, D.J. Callaghan, E.A. Jobbins, H. Tillander Council of Management: T.J. Davidson, R.R. Harding, L. M. Hudson, I. Mercer, J. Monnickendam, M.J. O'Donoghue, E. Stern, I. Thomson, V.P. Watson Members' Council: A.J. Allnutt, S. Burgoyne, P. Dwyer-Hickey, S.A. Everitt, J. Greatwood, B. Jackson, L. Music, J.B. Nelson, P.J. Wates, C.H. Winter Branch Chairmen: Midlands - G.M. Green, North East - N. R. Rose, North West - D. M. Brady, Scottish - B. Jackson, South East - C.H. Winter, South West - R.M. Slater Examiners: A.J. Allnutt, M.Sc, Ph.D., FGA, L. Bartlett, B.Sc, M.Phil., FGA, DGA, S. Coelho, B.Sc, FGA, DGA, Prof. A.T. Collins, B.Sc, Ph.D, A.G. Good, FGA, DGA, J. Greatwood, FGA, S. Greatwood, FGA, DGA, G.M. Green, FGA, DGA, G.M. Howe, FGA, DGA, S. Hue Williams MA, FGA, DGA, B. Jackson, FGA, DGA, G.H. Jones, B.Sc, Ph.D., FGA, Li Li Ping, FGA, DGA, M.A. Medniuk, FGA, DGA, M. Newton, B.Sc, D.Phil., C.J.E. Oldershaw, B.Sc (Hons), FGA, DGA, H.L. Plumb, B.Sc, FGA, DGA, N.R. Rose, FGA, DGA, R.D. Ross, B.Sc, FGA, DGA, E. Stern, FGA, DGA, S.M. Stocklmayer, B.Sc (Hons), FGA, Prof. I. Sunagawa, D.Sc, M. Tilley, GG, FGA, CM. Woodward, B.Sc, FGA, DGA, Yang Ming Xing, FGA, DGA The Journal of Gemmology Editor: Dr R.R. Harding Assistant Editors: M.J. O'Donoghue, P.G. Read Associate Editors: Dr C.E.S. Arps (Leiden), G. Bosshart (Zurich), Prof. A.T. Collins (London), Dr JW. Harris (Glasgow), Prof. R.A. Howie (Derbyshire), Dr J.M. Ogden (Hildesheim), Prof. A.H. Rankin (Kingston upon Thames), Dr J.E. Shigley (Carlsbad), Prof. D.C. Smith (Paris), E. Stern (London), Prof. I. Sunagawa (Tokyo), Dr M. Superchi (Milan) Production Editor: M.A. Burland Vol 28, No. 8, October 2003 ISSN: 1355-4565 Pearl cultivation in Donggou, Ezhou, Hubei, and cathodoluminescence of cultured pearls Huang Fengming, Yun Xinqiang, Yang Mingxing and Chen Zhonghui Gemmological Institute, China University of Geosciences, Wuhan 430074, P.R. China ABSTRACT: The paper summarizes the cultivation in Ezhou city, Hubei, P.R. China, of freshwater pearls in four stages: (1) the choosing and rearing of parent mussels, (2) the rearing of pearl-producing mussels, (3) the grafting operation and (4) the after-care of the mussels followed by the recovery of the non-nucleated cultured freshwater pearls. Additionally, the luminescent properties of cultured pearls under cathode rays are considered. Non-nucleated cultured freshwater pearls luminesce yellow, yellowish-green and green under cathode rays, with local orangey-red areas in some specimens. In contrast, nucleated cultured seawater pearls display no cathodoluminescence. These results are related to the environments in which the respective cultured pearls grew. Dyeing and irradiation treatments were found to suppress the luminescence of freshwater cultured pearls under cathode rays. The Raman spectra of 449 orangey-red areas in some non-nucleated cultured freshwater pearls are characterized by peaks at 281, 712 and 1085 cm-1, resembling those observed in inorganic calcite. The presence of a diffuse matrix of protein, such as carotenoid, may reduce the intensity of cathodoluminescence in coloured non-nucleated cultured freshwater pearls. Pearl cultivation in Donggou, The cultured pearl farm in Donggou is Ezhou one of the more important cultured freshwater pearl farms in China. The town t has been recorded that pearl cultivation of Donggou is located on the shore of Lake occurred as early as 1082 during the Song Liangzi, which is the second largest lake in IDynasty in ancient China (Pang, 1167, Hubei Province. Donggou is about 20 km from Xie 1995 et al.), but the greatest away from the Wuhan-Huangshi development of the pearl culturing industry expressway and is two hours by car from has taken place over the last 20 years (He, Wuhan. 1999; Shen, 2001). At present, the production of cultured freshwater pearls predominates, The pearl culturing industry in Donggou forming more than 90% of total world started more than 20 years ago and a wealth production, and is estimated to be around of experience in rearing pearl-producing 1600t annually (Sun, 2001). This compares mussels and in producing pearls has been with the annual production of 15-20t of accumulated. In recent years there has been cultured seawater pearls. an increase in local government funds for © Gemmological Association and Gem Testing Laboratory of Great Britain ISSN: 1355^565 in a body of water is 2:1 (Bian, 2001 b). The parent mussels must be suspended in gently flowing water. The rearing of pearl-producing mussels The sexual glands of Hyriopsis cumingi mature during the last ten-day period of April and the first ten-day period of May. Normally, mature Hyriopsis cumingi start to ovulate when water temperature reaches 18°C. In ideal growth conditions, including suitable water temperature, full food and oxygen supplies, and a supply of fresh and flowing water, each mussel can ovulate seven to eight times annually. If the water Figure 1: Hyriopsis cumingi used to produce temperature is low, the ovulation period cultured freshwater pearls in Donggou. may be delayed until September. The female mussels ovulate mature ova into their outer branchial or gill cavities, where the ova the development of agriculture, which combine with the sperm discharged into the includes the pearl culturing industry. At water by male mussels to form glochidiums. present in Donggou there are more than 20 Since the glochidiums cannot obtain sites covering about 2 x 107 km2 rearing nutrition directly from water, they then must approximately two hundred million pearl- attach themselves to the fins or gills of fish, producing mussels. These produce more which are deliberately placed in the pools 44945 0 than 90t of cultured freshwater pearls for this purpose, in order to absorb nutrition. annually. The cultured pearls from the There are two kinds of fish available to act as Donggou farm account for 85% of the total parasitic hosts - the yellowhead production of cultured freshwater pearls by (Pseudobagrus fulvidraco) and the bighead (a weight and about 67% by value for Ezhou city. variegated carp). In Donggou, Pseudobagrus fulvidraco (Figure 2) are used. On average, The stages of cultivation one fish may have 150-200 glochidiums attached. After four to fifteen days Choosing and rearing parent mussels depending on the water temperature (Li, Generally, for producing cultured 2000), the glochidiums metamorphose to freshwater pearls, the mussels Hyriopsis become young mussels, at which time they cumingi and Cristaria plicata can be used, and fall from the fishes. The young mussels are in Donggou, Hyriopsis cumingi (Figure 1) is the usually 0.3-10 mm long, and are transparent preferred species. The mussels are either (Figure 3). Groups of 80 to 100 young found wild in lakes, rivers or pools or are mussels are placed in bamboo baskets about bred. As parent mussels, they must be 40 cm x 40 cm x 11 cm in dimensions. During healthy and strong. The adductor muscle growth the young mussels must be fed, and should be strong and the shell must be of protected from disease and from attack by good shape. The parent mussels should be other animals such as fishes, shrimps, ducks, three to six years old and over 17 cm in water birds and other predators. width (Bian, 2001 a, b; Li, 2000; Wang, 2001). The male and female mussels should be The grafting operation from different sources in order to avoid When the young animals are about one inbreeding problems. Normally for breeding year old and about 7-10 cm in length, they purposes the ratio of female to male mussels are lifted out of the water and are ready for J. Gemm., 2003, 28, 8, 449-462 Figure 2: Yellowhead (Pseudobagrus fulvidraco) used as the parasitic host for glochidiums. the grafting operation. In order to produce (c)The strip of mantle is placed on a glass non-nucleated cultured freshwater pearls plate with the other epidermis facing pieces of mantle from a sacrificed mussel are upwards. The inner epidermis, which is 451 inserted into the incisions made in the pearl- facing downwards is sliced away. 449 producing host mussel. The sacrificed mussel variety is the same as the host mussel variety, i.e. Hyriopsis cumingi. Normally, the mussels providing the mantle tissue are less Figure 3: Young mussels which have just fallen than one year old and about 6-9 cm in from a yellowhead (Pseudobagrus fulvidraco). length. These young mussels have mantles with a strong metabolism, which are able to secrete nacre at a high rate, which is ideal for the formation of pearl sacs. The mantle tissue preparation is as follows (Bian, 2001c): (a) The adductor muscle is cut and the two halves of the bivalve are opened out to reveal the fleshy organism inside. (b)The coloured outer margin of the mantle is cut away, and then a strip of mantle with an elongate depression (along a similar depression in the shell underneath) (Figure 4) is removed.