89 / 2019-10-10 12:11:48

“重结晶”黄色蓝宝石的宝石学特征研究

重结晶宝石,黄色蓝宝石,天然宝石碎片,合成宝石

自二十世纪末起，珠宝市场上开始出现“再造”或“重结晶”宝石，商家声称生产这种“重结晶”宝石的原材料为天然宝石碎片或粉末，其生产成本高于使用普通化学物质作为原料的合成宝石，因此“重结晶”宝石的市场价格也高于普通的合成宝石并低于天然宝石。为了厘清“重结晶”宝石的本质，正确引导消费者有效判断其市场价值，采用常规宝石学仪器、拉曼光谱、红外光谱、紫外可见吸收光谱和激光剥蚀电感耦合等离子体质谱仪对日本ANUPAM GEMS公司的7颗“重结晶”黄色蓝宝石样品进行了测试和分析。
结果表明，该批“重结晶”黄色蓝宝石样品为单晶宝石，样品中均含有数量不等的圆形气泡，其中一颗样品（YS-4）颜色不均且含有半透明至不透明的无色或橙红色树枝状、网状包体。其红外光谱图中未出现与焰熔法和水热法相关的红外特征吸收峰。紫外可见吸收光谱在410nm附近有一较强的吸收宽带，是由Ni3+的d-d电子跃迁导致的，其在可见光区域产生的选择性吸收使宝石呈黄色。成分测试分析可得，“重结晶”黄色蓝宝石中几乎不含微量元素（仅有少量的Ni、Ti和Mg存在），而天然黄色蓝宝石通常含有大量的微量元素，特别是Fe。
综上所述，这批“重结晶”黄色蓝宝石实际上只是助熔剂法合成宝石，采用天然宝石碎片或者粉末作为原料的合成宝石被称为“重结晶”宝石来出售，只是商家的一种营销手段而已。
“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 different numbers of round gas bubbles. One of the samples (YS-4) is in uneven color and has colorless 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 410nm 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.