PMID: 30160389Mar 1, 2017Paper

Study on Color Quantitative Expression, Replication and Color Origin of Gray-Purple Nephrite from Qinghai, China Based on Spectroscopy Methods

Guang pu xue yu guang pu fen xi = Guang pu
Ze-min LuoMing-xing Yang

Abstract

Color is one of the most important factors in evaluating the quality and price of jewelry. Quantitative research on color of jewels has been a hotspot in gemological science. Whether for jewelry industry or gems research, observing and describing the gems’ color characteristics under transmission light is an essential method. This study focuses on building a research method to quantitatively characterize nephrite color, and to determine their color origin based on transmitted spectroscopy techniques. Natural gray-purple nephrite of Sanchahe mining, Qinghai, China was chosen as a typical subject due to its gradual-change color characteristic. We first quantitatively expressed and replicated the different color region on a gray-purple nephrite sample with given thickness (1.0 mm) with UV-Visible absorption spectra and 1976 CIE L*a*b* colorimetric parameters, as well as Adobe Photoshop software. The replicated color of light and dark color regions were both close to the transmitted color observed by naked eyes. It is inferred that the subtle color differences between naked eyes observation and transmitted spectroscopy replication may from the multiple effects of incident light in translucent polycrystalline structure, such as abso...Continue Reading

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