전자저널 > 전자저널 > UV-Vis and ED-XRF Analyses of Natural Black Colored Pearls from Freshwater Cultured Shells

UV-Vis and ED-XRF Analyses of Natural Black Colored Pearls from Freshwater Cultured Shells

Hea-Yeon Kim and Jong-Wan Park

Department of Materials Science and Engineering, Hanyang University, Seoul 133-791, Korea

Analyses of UV-Vis spectrum and reflectance are useful tools to identify pearls of which color was naturally madeor chemically changed. Contents of some trace elements of pearls by using ED-XRF may give us the informationthat the pearls were originated from marine shells or freshwater shells, and may give us whether the pearls werechemically treated or not. Three types of chemically untreated pearls, freshwater cultured, Akoya cultured andTahitian cultured, were treated with silver nitrate. UV-Vis absorbance spectrum of Ag was changed after treatment,and reflectance of pearls was decreased. Absorbance of natural black colored Tahitian cultured pearls at 400, 500and 700 nm was observed. Natural black colored freshwater cultured pearls showed two characteristic absorptionpatterns in UV-Vis spectra at 380-400, 480-500 nm. Unlike naturally black colored Tahitian cultured pearls, theabsorption spectrum at 700 nm could not be found from black freshwater cultured pearls. Manganese was notdetected in the pearls from marine shells, and strontium content of the pearls from marine cultured shells washigher than that from freshwater cultured shells. According to ED-XRF analysis, Ag contents of silver nitratetreated pearls increased as more time passed, because silver ion invaded to nacre layer of the pearls. Since Agcontent of the black pearls known as untreated ranged under 0.1%, analysis of Ag content may used to distinguishthe black pearls are treated or not in marketplace.

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