黄色配镶钻石中合成钻石的鉴定

小颗粒黄色合成钻石常会与天然黄色钻石混合出现在批量裸石中或是作为配石出现在各种镶嵌饰品中。近期,笔者在日常检测中,发现一枚祖母绿戒指配镶的263粒黄色钻石中混有合成钻石,为了探索镶嵌中的小颗粒黄色合成钻石与天然钻石的鉴别方法,笔者对所有的黄色配镶钻石做了尽可能的详细测试,包括显微镜下内部特征观察、不同能量下的紫外荧光和磷光观察(普通的宝石荧光灯、GV5000、DiamondView~(TM))、显微红外吸收光谱以及光致发光光谱等测试。分析结果表明,其中7粒钻石为高温高压合成钻石,其红外吸收光谱显示均为纯Ib型,不含聚合氮,不含任何与氢有关的吸收峰,而其余的天然黄色钻石主要为IaA-Ib或Ib-IaA型,含有与氢有关的吸收峰(1 405,3 107cm~(-1)等)或含有与孤氮有关的吸收峰(1 352,1 358cm~(-1)等),此外合成钻石荧光较强,颜色为亮绿色,而天然钻石荧光则很弱,所有的合成钻石都可以检测到弱的与镍有关的883/884nm双发光峰。因此根据显微红外吸收光谱特征辅以荧光观察等方法,可以将镶嵌中的小颗粒黄色合成钻石与天然钻石区分开来。

Identification of Melee-Size Synthetic Yellow Diamond in an Emerald-Diamond Ring

Melee-size synthetic yellow diamonds have appeared in the gem market, as loosestones or mountedin jewelries.Recently, the authors found that there were several HPHT synthetic yellow diamonds among 263 pieces of yellow diamonds mounted in an emerald-diamond ring during the conventional gem testing.In order to distinguish synthetic diamonds from natural counterparts in the diamond jewelries, the systematic investigation was performed for the mounted melee-sized yellow diamonds, by using ultraviolet fluorescence,DiamonView?, micro-infrared spectroscopy, photoluminescence spectroscopy, etc.The results showed that 7 pieces of melee-sized yellow diamonds are HPHT synthetic diamonds, all of them are pure type Ib, with ignorable aggregate nitrogen and no hydrogen in the mid-infrared absorption.The natural yellow diamonds are mainly type IaA-Ib and Ib-IaA,with the hydrogen-related absorptionlines at 1 405, 3 107 cm-1, etc, and single nitrogen related peaks at 1 352,1 358 cm-1, etc.Additionaly, the synthetic diamonds have strong and bright green fluorescence, the natural ones have very weak or none.The nickel-related lines at 883, 884 nm in 7 pieces synthetic diamonds could be detected.Therefore, the combination of micro-infrared spectroscopy with fluorescence characteristics is an effective method for rapid and accurate separation of melee-sized natural and synthetic diamonds.