Experimental cation redistribution in the tourmaline lucchesiite, CaFe2+3Al6(Si6O18)(BO3)3(OH)3O
Natural Mg-rich lucchesiite was thermally treated in air and hydrogen atmosphere up to 800 °C to study potential changes in Fe-, Mg- and Al ordering over the octahedrally coordinated Y- and Z-sites, and to explore possible applications to intracrystalline geothermometry based on tourmaline. Overall, the experimental data (structural refinement, Mössbauer, infrared and optical absorption spectroscopy) show that thermal treatment of lucchesiite results in an increase of Fetotcontents at Z balanced by an increase of Mg and Al at Y.