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http://dx.doi.org/10.9727/jmsk.2015.28.1.9

Mineralogical Studies on Luster of Seawater Cultured Pearls, Tongyeong, Korea  

Cho, Hyen Goo (Department of Earth and Environmental Sciences and Research Institute of Natural Science, Gyeongsang National University)
Kim, Soon-Oh (Department of Earth and Environmental Sciences and Research Institute of Natural Science, Gyeongsang National University)
Do, Jin Young (School of Cultural Assets, Gyeongju University)
Publication Information
Journal of the Mineralogical Society of Korea / v.28, no.1, 2015 , pp. 9-16 More about this Journal
Abstract
A mineralogical analysis on the factors affecting the luster of pearls was carried out using gravity measurement, optical microscope observation, X-ray diffraction analysis, and scanning electron microscopy. We divided the seawater cultured pearls from Tongyeong into the following four types based on luster and shape; good luster and round (LR), lackluster and round (LLR), lackluster and baroque (LLB), and lackluster and two nucleus (LTN) pearls. Pearls with high-quality luster had slightly lower specific gravity as compared to pearls with low-quality luster, but both these types of pearls are within the specific gravity range of commercial pearls. Regarding the cross-sectional thickness of the mother-of-pearl layer, LR pearls showed a uniform thickness of about 0.3 mm in average. On the other hand, LLR pearls were characterized by relatively thinner, but uniform thickness. LTN and LLB pearls showed a tendency of significantly large variation in thickness even within a single pearl. For the surface of pearls, pearls with high-quality luster showed narrower and clearer growth lines of aragonite crystals as compared to pearls with low-quality luster. Pearls with high-quality luster were characterized by fewer aragonite crystal lattice defects as compared to pearls with low-quality luster, and the former showed parallel arrangement, thinner thickness, and less difference in thickness on the surface and inside. If a pearl has a prismatic layer, it is composed of aragonite with calcite in the prismatic and nacreous layer, and calcite content is very high in the lackluster pearl. Pearls without a prismatic layer were devoid of calcite irrespective of their quality of luster, and were composed of aragonite.
Keywords
seawater cultured pearl; nacreous layer; luster; prismatic layer; aragonite; calcite;
Citations & Related Records
Times Cited By KSCI : 4  (Citation Analysis)
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