X-Ray powder diffraction - structure prediction of unknown stone using FullProf and GSAS - Rietveld Refinement

A slightly violetish blue, cone shaped, hexagonally soft sheen, a soft lustre on a surface, and semi/nearly transparent with reasonable weight of a natural stone has been analysed as a part of investigation for determining the components of the stone thereby leading to identify as to whether the stone is in a category of gemstone, radioactive elements, or otherwise. Philips, X-pert Pro, DY993 X-ray Powder Diffractometer has been employed for collecting the powder diffraction data in the Bragg-Brentano geometry using proportional counter in the 5° < 2θ < 85° range at room temperature 300 K. The data, thus, obtained from the XRPD has been used in FullProf and GSAS (General Structure Analysis Software) software with the Rietveld refinement technique for elucidating the possible molecular structure of the unknown stone. In addition to the XRPD technique, the physical and optical parameters such as specific gravity, hardness, luster, transparency, cleavage, streak and other associated minerals have also been measured. This study reveals that the stone is in a category of precious stone which is of mineral deposition Corundum, a blue sapphire. The structure has been determined from Rietveld analysis in space group R-3c, with a= 4.7655 (2) Å and c = 13.0132(3) Å.