Gemmological Characteristic of "Recrystallized" Emerald

Recently, a kind of "recrystallized" emerald has appeared in the market. In order to validate its authenticity, on the basis of conventional gemmological testing, several 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 six "recrystallized" emerald samples have been discussed.The inclusions of the samples include pyrite, water-ripple pattern, gas-liquid two-phase inclusion, and healed cracks. The chemical composition of the sample is of w(Al₂O₃)=18.48%-18.79%, w(SiO₂)= 65.93%-66.19%, and w(Be)=49 700 ppm-50 700 ppm. The trace elements are rich in vanadium and poor in iron. The infrared spectra of the samples shows absorption peaks of type Ⅰ water (5 102, 5 456 cm^-1) and type Ⅱ water (5 272 cm^-1), and the absorption peaks of type Ⅱ water were stronger, which were different from those of natural emerald. The ultraviolet-visible spectra of the samples shows absorption of chromium, iron and vanadium ions in one category, and absorption of chromium and vanadium ions in the other. Raman spectra of the samples show the Be-O telescopic vibration (1 067 cm^-1), deformation vibration of Si-O-Si (683 cm^-1) and lattice vibration (3 21.5 cm^-1), with the FWHM of 683 cm^-1 less than 8.6 cm^-1, which is consistent with the spectral peaks of hydrothermal synthetic emeralds.The results show that the recrystallized emeralds accord with the characteristics of hydrothermal synthetic emeralds, among which, the samples containing pyrite may take the natural emeralds containing pyrite as seed crystals, and other samples have no characteristics indicating natural genesis. The so-called "recrystallized" emeralds are more of a gimmick to attract customers.