Photochromic gemstones exhibit optically controllable coloration at ambient temperatures, strongly affecting their visual appearance and potential market value. As a result, a comprehensive study of characteristic photochromic properties is required to estimate the potential influence on gemstone evaluation. A UV-Visible absorption spectrometer integrating a tunable light source for external excitation has been developed to investigate the wavelength- and time-dependence of photochromism for colored gemstones, focusing on natural, laboratory-grown, and color-treated pink diamonds. The results can be used to develop a color stabilization protocol to improve the reliability of color grading for valuable gemstones.
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