Synthesis and Crystal Structure of Zn-Bearing Tourmaline

Tourmaline is a common borosilicate, an important indicator of mineral formation conditions, and a promising material for various technological applications. Crystals of a Zn-bearing tourmaline analogue with a zinc content of up to 4.22 wt % ZnO, typical of natural tourmaline crystals, are obtained by hydrothermal synthesis in boron-chloride solutions at temperatures of 400–650°C and pressures of 60–150 MPa. The morphology is studied, the composition is analyzed, the crystal structure is refined, and the spectroscopic characteristics are established, as well as the effect of pressure and temperature on the composition and growth rate of tourmaline are determined. Synthetic Zn-bearing analogue of alumino-oxy-rossmanite with the crystal-chemical formula X( _ 0.95 Na0.03Ca0.02)Y(Al2.88Zn0.12)Z Al_6.00T (Si6O18)(BO3) ₃V (OH2.05O0.95)WO crystallizes in R3m space group with the unit cell parameters: a = 15.7596(2) Å, c = 7.0623(1) Å. Using Raman spectroscopy, it is shown that the intensity ratio of the bands associated with the (YO6) octahedra at ~230 and 270 cm–1 depends on the zinc content in the structure of the Zn-bearing tourmaline analogue.