Speaker
Description
Yellow sapphire is a gemstone variety of corundum (Al2O3). The yellow color is commonly caused by Fe3+ impurity substituting for Al3+ in the Al2O3 structure. The depth of yellow color is linked to Fe3+ concentration. The higher content of Fe3+ produces a deeper yellow color. The quantitative relationship between color and the chemistry of natural corundum has been comprehensively studied [1]. However, some chromophores are low content of the impurity such as Be2+ in cooperating with low content of Fe3+ to produce the yellow color in yellow sapphires [2]. It is difficult to differentiate between the natural yellow sapphire caused by high Fe3+ content and the beryllium-treated yellow sapphire by naked eyes. Some advanced techniques to identify the Be heat-treated yellow sapphire have been practiced such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser-induced breakdown spectroscopy (LIBS). We measured the colors of natural and beryllium-treated yellow sapphires by UV-Vis reflectance spectroscopy. The concentration of impurities in the sapphire samples was measured by the LA-ICP-MS technique. To compare the yellow colors of CIELch, we found that the hue values of the beryllium-treated yellow sapphires were higher than the natural yellow sapphires.
Key words: Corundum, Natural yellow sapphire, Beryllium-treated yellow sapphire, Color measurement
[1] Dubinsky E V, Stone-Sundberg J and Emmett J L 2020 Gems & Gemol. 56 2-28
[2] Monarumit N, Lhuaamporn T, Sakkaravej S, Wathanakul P and Wongkokua W 2020 J. Phys. Commun. 4 105018
