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Aragonite observed in the prismatic layer of seawater-cultured pearls |
| MA Hongyan1, QIN Zuolu1, TONG Zhangfa1, QIU Shuheng1, ZHANG Beili2, LEE I-S3 |
| 1.College of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China; 2.National Gemstone Testing Center, Beijing 100013, China; 3.Institute of Applied Physics and Yonsei Center of Nanotechnology, Yonsei University, Seoul 120-749, Korea; |
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Abstract The prismatic layer is obviously different from the parallel layer in seawater-cultured pearls. X-ray diffraction (XRD), optical microscopy (OM) and micro-infrared (IR) spectroscopy have been applied to characterize the crystallized layers of high- and low-quality seawater-cultured pearls produced in South China. The result shows that the prismatic layer is not only composed of calcite as reported in previous researches. Three types of prisms were found in seawater-cultured pearls: calcite prism, aragonite prism and calcite and aragonite prism. Therefore, we have a new understanding of the biomineralization of the prismatic layer in seawater-cultured pearls. The result makes us review the traditional viewpoint that the increased content of aragonite improves the quality of pearls. We discovered that some seawater prismatic pearls almost completely composed of aragonite have the worst quality. We thought that the thickness and the spatial distribution of prisms are the main factors that can affect the quality of seawater-cultured pearls.
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Issue Date: 05 September 2007
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