市场上“重结晶祖母绿”的鉴定特征

Identification Characteristic of“Recrystallized Snythetic Emerald”

近年来市场上出现了一种声称由天然祖母绿粉末重结晶而成的“重结晶祖母绿”。为了探明其鉴定特征,在常规宝石学测试的基础上,采用LA-ICP-MS、红外光谱、紫外-可见吸收光谱、拉曼光谱等测试方法,从宝石学特征、化学成分及光谱学特征对6颗“重结晶祖母绿”样品进行研究。结果显示,样品内含物有水波纹、气液两相包裹体、愈合裂隙等,化学成分w(Al_(2)O_(3))=18.48%~18.79%,w(SiO_(2))=65.93%~66.19%,w(Be)=49700×10^(-6)~50700×10^(-6),微量元素具有富V贫Fe的特征;红外光谱在2326、5102、5272、5456、6817 cm^(-1)和7143 cm^(-1)处有吸收峰,在4000~3400 cm^(-1)范围内存在宽吸收带,表明样品既含有Ⅰ型水也含有Ⅱ型水;紫外-可见吸收光谱一类显示Cr^(3+)、Fe^(3+)和V^(3+)的吸收,另一类显示Cr^(3+)和V^(3+)的吸收;拉曼光谱显示Be-O伸缩振动(1067 cm^(-1)处),Si-O-Si变形振动(683 cm^(-1)处)和晶格振动(321.5 cm^(-1)处)。综合结果表明,“重结晶祖母绿”符合水热法合成祖母绿的鉴定特征,未见指示天然成因的特征。所谓的“重结晶祖母绿”名称更多的是商家吸引顾客的噱头,其商品应正确定名为合成祖母绿。

Recently,a kind of“recrystallized emerald”that claims to be created from natural emerald powder appeared in the market.In order to figure out its identification characteristics,on the basis of conventional gemmological testing,several other testing instruments were used,such as laser ablation inductively coupled plasma mass spectrometry,Fourier transform infrared spectrometer,ultraviolet visible spectrophotometer,and laser Raman spectrometer.The gemmological characteristics,chemical compositions and spectroscopy characteristics of 6“recrystallized emerald”samples were tested.The inclusions of the samples include water-ripple pattern,gas-liquid two-phase inclusion,and healed cracks.The chemical composition of the sample is w(Al_(2)O_(3))=18.48%~18.79%,w(SiO_(2))=65.93%~66.19%,and w(Be)=49700×10^(-6)~50700×10^(-6).The trace elements are rich in V and poor in Fe.The infrared spectra of the samples showed absorption peaks at 2326,5102,5272,5456,6817,7143 cm^(-1) and a wide absorption band in the range of 4000~3400 cm^(-1),which indicates that the samples contain both typeⅠwater and typeⅡwater.The UV-Vis spectra of the samples showed absorption of Cr^(3+),Fe^(3+)and V^(3+)in one category,and absorption of Cr^(3+)and V^(3+)in the other.Raman spectra of the samples showed the Be-O telescopic vibration(1067 cm^(-1)),deformation vibration of Si-O-Si(683 cm^(-1))and lattice vibration(321.5 cm^(-1)).The results showed that the characteristics of the“recrystallized emeralds”accord with the characteristics of hydrothermal synthetic emeralds,and no evidence indicates natural genesis.The so-called“recrystallized emerald”is more a gimmick for businesses to attract customers.The“recrystallized emerald”should be correctly named as synthetic emerald.