Multielemental analyses of isomorphous Indian garnet gemstones by XRD and external pixe techniques

Garnet gemstones were collected from parts of Eastern Ghats geological formations of Andhra Pradesh, India and their gemological studies were carried out. Their study of chemistry is not possible as they represent mixtures of isomorphism nature, and none of the individual specimens indicate independent chemistry. Hence, non-destructive instrumental methodology of external PIXE technique was employed to understand their chemistry and identity. A 3 MeV proton beam was employed to excite the samples. In the present study geochemical characteristics of garnet gemstones were studied by proton induced X-ray emission. Almandine variety of garnet is found to be abundant in the present study by means of their chemical contents. The crystal structure and the lattice parameters were estimated using X-Ray Diffraction studies. The trace and minor elements are estimated using PIXE technique and major compositional elements are confirmed by XRD studies. The technique is found very useful in characterizing the garnet gemstones. The present work, thus establishes usefulness and versatility of the PIXE technique with external beam for research in Geo-scientific methodology.

► For the first time, External PIXE technique was employed to analyse the East Indian garnet gemstones.
► The trace and minor elements are estimated using External PIXE technique.
► Major compositional elements are confirmed by XRD (Crystal structure & lattice parameters).
► Almandine variety of garnet gemstone is found to be abundant fraction in the present study.