Dr. Ahmadjan Abduriyim

Dr. Ahmadjan Abduriyim is the president of Tokyo Gem Science company and the director of GSTV Gemological Laboratory. He was the former senior research scientist and senior manager of colored stones identification service in GIA Tokyo laboratory. Abduriyim received his doctorate in mineralogy from the Division of Earth and Planetary Science at Kyoto University in Japan. He has worked on the identification of natural, synthetic and treated diamonds, colored stones and pearls, as well as on the geographic origin determination of major gemstones and the applications of LA-ICP-MS in gemology. Numerous gemological articles were published in major gemological and geoscience periodicals such as Gems and Gemology, Diamond and Related Materials, Journal of Mineralogical and Petrological Science, Australian Journal of Earth Science, Journal of Raman Spectroscopy, Journal of Crystal Growth. He has received several Dr. Edward J. Gübelin Most Valuable Article Awards and Most Valuable Presentation and Promotion awards in international conferences.

The gemological characteristic of Japanese Freshwater Cultured Pearls from the Lake Kasumigaura


The Lake Kasumigaura is the only source of freshwater beaded cultured pearl in Japan nowadays. This presentation introduces the history of Japanese freshwater pearl cultivation, which started in 1935. A new hybrid species of Hyriopsis schlegelii x Hyriopsis cumingii has been developed in Kasumigaura lake, Ibaraki prefecture in 1962 and a high quality beaded cultured pearl with thicknesses of around 3 mm is produced in a very limit amount per year. This study presents the results of UV-Vis spectroscopy, fluorescence testing and chemical analysis performed on various colored pearls and mollusks. The Japanese “Kasumiga pearl” produced by the Hyriopsis hybrid can be differentiated from Chinese beaded freshwater pearls from the same species by using trace element analysis.

Impressions from the first EGS 2007 in Idar-Oberstein

Register for the European Gemmological Symposium
on May 24 – 26, 2019 in Idar-Oberstein.

During the two days’ conference, you will enjoy numerous internationally recognized and distinguished speakers, as well as a broad spectrum of subjects including diamonds, coloured stone, pearls and jewellery.

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