Gemmological Characteristic of "Recrystallized" Yellow Sapphire

"Reconstructed" and "recrystallized" gemstones began to appear in the jewelry market since the late 20th century. Unlike synthetic gemstones made from chemical materials, the merchants claim that the raw materials of "recrystallized" gemstones are natural gem fragments or powders and sell them at prices higher than synthetic gems but lower than natural ones. In order to figure out the nature of "recrystallized" gemstones and help consumers make sound judgement of their market value, 7 "recrystallized" yellow sapphires from Anupam Gems Japan Ltd are analyzed by conventional gemmological instruments, Raman spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS).The results show that these gems are single crystals, and that they all contain differentamounts of round gas bubbles. One of the samples (YS-4) is in uneven colour and has colourless or orange-red dendritic and mesh-like inclusions which range from translucent to opaque. The absorption peaks related to flame fusion or hydrothermal method are not found in the infrared spectra. There is a strong absorption band around 410 nm in the UV-Vis absorption spectrum caused by the d-d electron transition of Ni³⁺, and its selective absorption in the visible region makes the gems yellow. According to the chemical composition analysis, "recrystallized" yellow sapphires contain few trace elements (with only a small amount of Ni, Ti and Mg), while natural yellow sapphires usually show a greater number of trace elements, especially Fe.In summary, these"recrystallized" yellow sapphires are actually flux-grown synthetic gemstones. Synthetic gemstones made by natural gemstone fragments or powders marketed as "recrystallized" gemstones turn out to be a marketing ploy of merchants.