Determination of Mineral Compositions of New Kinds of Imitated Turquoise by FTIR-XRD-XRF

Identification of turquoises and corresponding imitations is commonly determined by Fourier Transform Infrared (FTIR) Spectrometer. Previous studies have shown that imitation turquoise was mainly composed of a single mineral phase such as hemimorphite, gibbsite, variscite, hydroxyl datolite, or magnesite. Fourier Transform Infrared (FTIR) Spectroscopy, X-ray Diffraction (XRD) and X-ray Fluorescence Spectroscopy (XRF) were used to investigate new kinds of imitation turquoises in order to classify them based on their mineral compositions and the method is described in this paper. Mineral compositions, crystal phases and crystalline appearance of different types of imitation turquoises were also compared. Results show that new kinds of imitation turquoises in this study can be mainly classified into three groups. The first group is mainly composed of silicate (larnite) and carbonate (calcite). The second group is composed of mixtures of calcite and dolomite. The third group consists of silicate, and minor barium feldspar, pyroxene and quartz. The mineral compositions of new kinds of imitation turquoises were significantly different from those of traditional imitations. In other words, the mineral compositions of imitation turquoises are becoming more and more diverse and complicated, which implies a higher demand for jewelry inspection agencies and researchers.