Nondestructive identification of gemstones by using a portable XRF–XRD system: an illuminating study for expanding its application in museums

Abstract

Nine gemstone samples were analysed by using a portable X-ray fluorescence-X-ray diffraction (XRF-XRD) system without any destructive preparation processes. The samples were measured by groups based on the transparency and the complexity of molecular structure. The XRF and the XRD measurements for each sample were performed simultaneously.The key experimental parameters were optimized in order to obtain XRD patterns acceptable for phase identification in a limited time. The XRF spectrum of each sample was analysed first to acquire the elemental composition qualitatively, and the information was then applied to refining possible phases. The phase analysis process of each sample was described in detail and the most likely phases were determined. Normal XRD experiments were conducted in order to verify the results. Advantages, disadvantages and applicable range of the system were analysed. The results indicate that the portable XRF-XRD system can be applied to identifying particular gemstones effectively, while single-crystal gems may not be identified very well. Wider recognition and application of the portable XRF-XRD system in cultural heritage and gemological fields call for hardware development, software updating and more real application cases.

Identification of cinnabar existing in different objects using portable coupled XRF-XRD, laboratory-type XRD and micro-Raman spectroscopy: comparison of the techniques

“…8c it can be seen that the major peaks fitted the lines well, which proves that cinnabar is the major component in the sample. However, there still remained some peaks which cannot be recognized by the system, which may be originated from the trace additives or impurity substances, or caused by the absence of some featured lines, as a defect of the software [15]. Raw mineral and polished gemstone samples were both regarded as mainly composed of cinnabar, but the pattern characteristics and the phases identified were different.…”

“…The Raman technique is regarded as non-destructive provided that appropriate working modes and parameters are adopted. Compared with XRD and infrared methods, however, Raman is weak in the scale of standard spectra database, the difficulty of spectra analysis, and the availability of instruments [15]. As for the curators, Raman spectroscopy is an ideal non-destructive method for the identification of unknown pigments, minerals, patinas, etc., provided that the key instrumental parameters for the similar objects have been determined and the differences between similar objects have been considered carefully.…”