Gemmological Characteristic and Spectroscopy Feature of Afghanite

In order to analyze the basic gemmological properties and spectroscopy features of afghanite, a series of systematic studies were conducted with the help of standard gemmological methods, X-ray powder diffraction, infrared absorption spectroscopy, laser Raman spectroscopy. The conventional gemmological testing revealed that afghanite was doubly refractive with a refractive index(RI) of 1.522 to 1.529 with a hardness of 5 to 6. These samples displayed varying degrees of bright orange to yellow fluorescence under longwave UV radiation. UV-Vis spectrum showed a wide absorption band centered at approximately 600 nm, which is proprotional to the colour depth of blue, and a weak absorption band centered at approximately 380 nm. Fluorescence and UV-Vis spectra were both influenced by S^3- and S^2-. The FTIR spectra of afghanite in the region between 4 000—400 cm^-1 showed that the main peaks at 684, 665, 614, 593, 544, 433, 1 005, 1 119 cm^-1 were accompanied by a shoulder peak at 1 166 cm^-1, and two weak peaks at 768, 1 378 cm^-1 in the fingerprint region, as well as two bands at 3 438, 1 631 cm^-1 in the functional region which corresponded to water molecules. Raman spectra of substrate part of rough samples showed that the characteristic peaks of afghanite were at 260, 426, 453, 542, 579, 615, 989, 1 083 cm^-1. The testing result of XRD showed that the five strongest peaks at d=3.682, 3.293, 2.125, 4.825, 2.678 Å, which belong to characteristic diffraction peaks of afghanite. In addition, LRM testing confirmed that blue mineral inclusions were lapis lazuli and paragenetic minerals contaning apatite, diopside, calcite, pyrite and sodalite, which were comfirmed by the result of XRD.