Transition-Metal Composition, Optical Absorption, and Channel-Water Characteristics of Natural V-Rich Beryl from the North Muzart River Area, Xinjiang, China

Natural V-rich green beryl from the North Muzart River area, Xinjiang, was investigated using microscopy, EDXRF, UV–Vis–NIR, FTIR, and Raman spectroscopy. Ten specimens were examined microscopically; selected detached crystals were analyzed spectroscopically. Thirteen EDXRF analyses on seven detached crystals yielded V2O5- and Fe2O3-equivalent contents of 0.562–4.616 wt.% and 0.172–0.494 wt.%, respectively; Cr2O3 was not detected under the present analytical conditions, and normalized Fe2O3–V2O5–Cr2O3 compositions plot near the V2O5 endmember. Broad absorption bands near 429 and 617 nm fall within the spectral range commonly attributed to V3+ in beryl. Given the V-dominant EDXRF composition, these bands are interpreted as predominantly V-related; however, the V3+ assignment remains indirect because EDXRF does not determine the oxidation state, crystallographic site, or local coordination of V, and a minor contribution from Cr below the EDXRF detection capability cannot be excluded. Weaker responses near 366, 391, and 847 nm may involve Fe-related centers. Raman spectra from two selected green regions are consistent with the beryl host, and FTIR spectra of four selected crystals indicate predominantly type-II channel-water features with weaker type-I contributions. These samples provide a natural comparative system for evaluating V-related absorption in beryl and for comparison with V-doped synthetic beryl.