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Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics

Although today’s global freshwater cultured pearl market is mostly dominated by Chinese products, Japanese freshwater pearl cultivation started in 1935. Lake Biwa in Shiga Prefecture supplied pearls in a wide variety of colors to the domestic and international markets until 1982. Due to water pollution and the depletion of Hyriopsis schlegelii , some of the pearl farms relocated to Lake Kasumigaura in Ibaraki Prefecture starting in 1962. Today the annual production of large nucleated cultured pearls at Lake Kasumigaura is below 40 kg, a small portion of which are supplied to the international market. This report investigates “Kasumiga pearl” culturing and describes the quality and production volume. UV-visible spectroscopy, fluorescence testing, and chemical analysis were performed on pearls in six different colors collected from the Hyriopsis schlegelii × Hyriopsis cumingii hybrid mollusk farmed at Kasumigaura.