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The change in surface compositional and bulk structural characteristics of the natural ruby stone, before and after heat treatment with lead oxide has been analyzed using two advance characterization techniques like: X-ray micro CT scan (μ-CT) and electron probe micro analyzer (EPMA). The analytical correlation between these two techniques in identification as well as in depth study of the ores and minerals before and after processing has been presented. Also, we describe the aesthetic enhancement of a low quality defective ruby stone by lead oxide filling and the sequential analysis of this ruby stone before and after treatment using these two advanced techniques to identify and to confirm the change in its aesthetic value. The cracks healing and pores filling by the metal oxide on the surface of the ruby have been analyzed using μ-CT and EPMA. Moreover, in this work we describe the advance characterization of the repaired gem stones especially ruby stones. This work will light up the path for in-depth understanding of diffusion mechanism and abstract information of impurity particles inside the minerals. Based on these observations, EPMA and micro CT are shown to be powerful tools for the identification as well as research in gem stones. [ABSTRACT FROM AUTHOR]

The colourless natural topaz stones were surface modified to beautiful yellow and green colour after heat treatment with lead oxide (PbO) and chromium oxide (CrO 3 ), respectively. The surface of topaz shows a uniform colouration over the whole structure, which is confirmed by the UV–vis spectroscopic study. The absorption bands in the range 390–440 nm and 646 nm in PbO and CrO 3 treated samples are associated with the yellow and green colouration of the stone. The chemical composition and oxidation states of the components present in the un-treated and treated topaz samples were determined from X-ray photoelectron spectroscopy (XPS) study, which clearly signifies that the stone retains its structure after treatment. Also, shifts of prominent peaks were observed in XRD and Raman spectra after heat treatment. Pb and Cr incorporation promotes oxygen vacancies in the topaz matrix, which is confirmed from the Raman peak at 223 and 220 cm −1 respectively. As deduced from Raman and XPS spectra, defect centers produced due to the oxygen vacancy and electronic charge transfer between topaz matrix with metal ions are the prime factor for the observed colour on topaz surface. [ABSTRACT FROM AUTHOR]

The surface behavior of the natural ruby stones before and after heat treatment with metal oxide additives like: zinc oxide (ZnO) and lead oxide (PbO) have been studied. The surface appearance of the ruby stones processed with the metal oxides changed whereas the bulk densities of the stones remained within the range of 3.9–4.0 g/cm 3 . The cracks healing and pores filling by the metal oxides on the surface of the ruby have been examined using scanning electron microscopy. The chemical compositions based on the XPS survey scans are in good agreement with the expected composition. The phase and crystallinity of the ruby stones original and heat-treated were obtained from their X-ray diffraction patterns. The change in peak separation between R 1 and R 2 – peaks in photoluminescence spectra and the contrary binding energy shift of the Al 2p peaks in the X-ray photoelectron spectra have been explicated. Moreover, in this work we describe the change in surface chemical and physical characteristics of the ruby stone before and after heat treatment. [ABSTRACT FROM AUTHOR]