R2: Crystal structure, crystal chemistry, physical properties of minerals, crystal growth and applied mineralogy

[R2-14] Crystal structure change in the grossular-Si-free katoite solid solution: oxygen position splitting in katoite

*Atsushi Kyono¹, Shubhi Arora¹ (1. Univ. of Tsukuba, Life & Environmental Sci.)

Keywords:Hydrogrossular, Hydrogarnet substitution, Single-crystal X-ray diffraction, Raman spectroscopy

Single crystals of katoite hydrothermally synthesized were examined by single-crystal X-ray diffraction, EPMA, and Raman spectroscopic techniques. Chemical formulas of the katoite fall inside the miscibility gap proposed by Kyritsis et al. (2009). In two katoites with chemical formulas, Ca₃Al₂(SiO₄)_0.57(H₄O₄)_2.43 and Ca₃Al₂(SiO₄)_0.69(H₄O₄)_2.31, O atom position was split into two independent crystallographic sites, O1 and O2. The results of Raman spectroscopy strongly suggest that there are two kinds of OH stretching vibration in the siliceous katoite.