Formation of hydrous, pyroxene related, phases from LiAlSiO4 glass in high pressure hydrothermal environments

Hydrous Al-bearing pyroxene-related phases were synthesized by subjecting LiAlSiO4 glass to hydrothermal environments at pressures of 5–10 GPa and temperatures of 400–600 °C. LiAlSiO3(OH)2 formed at 5 GPa, whereas at 10 GPa, product mixtures of LiAlSiO3(OH)2 and Li3Al4(Si2O7)(SiO3)2(OH)5 were obtained. The monoclinic structure of LiAlSiO3(OH)2 has been previously characterized from single-crystal X-ray diffraction data (Spektor, K.; Fischer, A.; Haussermann, U. Crystallization of LiAlSiO4 Glass in Hydrothermal Environments at Gigapascal Pressures–Dense Hydrous Aluminosilicates. Inorg. Chem. 2016, 55 (16), 8048−8058, 10.1021/acs.inorgchem.6b01181). It resembles that of α-spodumene (LiAlSi2O6) and constitutes alternating layers of chains of corner-condensed SiO4 tetrahedra and chains of edge-sharing AlO6 octahedra. OH groups are part of the octahedral Al coordination and extend into channels provided within the SiO4 tetrahedron chain layers. The structure solution of Li3Al4(Si2O7)(SiO3)2(OH)5, as detailed h...