Gemmological Characteristic of Green Kyanite

Green kyanite with unique filmy perception rarely appears in domestic gem market. In order to study its gemmological properties and colour origin, technologies like Raman spectroscopy, laser ablation-inductively coupled plasma mass spectroscopy (LA-ICP-MS), ultraviolet-visible spectroscopy (UV-Vis) and photoluminescence spectroscopy (PL) are resorted together. Spectroscopic results suggest that the filmy perception of the green kyanite comes from massive round quartz and short needle-liked talc inclusions, and its green body colour is ascribed to the selective absorption of the electron transitions of iron (Fe) and chromium (Cr). Fe and Cr absorb light in blue-violet and orange-red region respectively, and result in a green transmission window near 500 nm. With the increase of Fe concentration, samples appear yellowish tone, while a bluish tone appears with the increase of Cr concentration. PL spectra show that 410 nm and 580 nm light can excite the red fluorescence of the samples effectively. Therefore, it is considered that the Fe absorption bands in the ultraviolet region are the cause of the inertia appearance of the green kyanite samples under gemmological ultraviolet fluorescent lamp.