Color Fading Experiment and Unstable Color-centers

Fig. 3 Different colors produced by the new treatment (including pink, yellow, orange, and blue) are sorted for this report. Sapphires of different colors are accidentally clustered together by the melting of minerals other than sapphire during heat treatment with the new E(IM1) method. Only a small portion of the sapphires showed this accidental cluster. Note: Different colors are produced in the same heating runs. Fig. 4 Natural Blue and white E(IM1)-enhanced sapphires exposed to the UV treatment experiments. One half of the piece was kept for reference (left side). Both the blue and white sample developed yellow and orange rims respectively. These rims were found to be the zone of Be-enrichment by LA-ICP-MS (See Fig. 42 and Fig. 57). The color is found to be unstable. The orange rims are fading after mild exposure to heat.

Fig. 5 Polarized UV-VIS-NIR absorption spectra of the yellow sapphire before and after treatment with UV light. Yellow curve: Spectrum after exposure to UV. Black curve: After fading of yellow sapphire to white color. Note: Shift of the absorption spectrum towards higher absorptions in the blue causes the yellow color in the sapphires due to the presence of color centers.

Fig. 6a Fluorescence experiment with Eickhorst UV Lab lamp (long wave 366nm) on faceted sapphires, which had previously been subjected to the new treatment. Left: Orangy-pink sapphires (origin: Madagascar) showing intense orangey fluorescence with more yellowish fluorescence at rim. At right: two samples (origin: Songea) with medium orange-red fluorescence (Faceted gemstones between 2 and 5 cts in size). Note: Yellowish fluorescence is confined to the rim of the gemstones (Fig. 6b)

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