R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

4:15 PM - 4:30 PM JST(7:15 AM - 7:30 AM UTC)

[R1-03] Horiite, a new mineral, from Taguchi mine, Aichi Prefecture

*Daisuke HAMANE¹, Mariko Nagashima², Yuki Mori³, Masayuki Ohnishi, Tomohiro Ishizaka, Shinji Inoue (1. The University of Tokyo, 2. Yamaguchi University, 3. JASRI)

Keywords:

Horiite,Yoshimuraite,hejtmanite,bafertisite group,seidozerite supergroup

Sokolova and Cámara (2016) systematized the group of minerals with a titanium silicate (TS) blocks in their structure and proposed the seidozerite supergroup. Among them, the group of minerals with Ti = 2 apfu is classified as the bafertisite group, and yoshimuraite and hejtmanite also belong to this group. In this study, we discovered an unknown bafertisite group mineral and clarified its occurrence, chemical composition, and crystal structure. This mineral was named to be horiite after Dr. Hidemichi Hori (1934-2019) and approved as new mineral by IMA-CNMNC. It occurs mainly in quartz veins and is very similar in appearance to hejtmanite, but has strong compositional and structural similarities with yoshimuraite. The ideal chemical formula of horiite is Ba₂Mn₂Mn₄Ti₂(Si₂O₇)₂(PO₄)₂O₂ (OH)₂. The TS block that characterizes the crystal structure consists of Mn(O,OH)₆, TiO₆ octahedra, and SiO₄ tetrahedra. An intermediate (I) block also contains PO₄ tetrahedra, Ba and Mn polyhedra. This feature is similar to yoshimuraite, but there are differences in Ti coordination number (TiO₆ vs. TiO₅), PO₄ configuration, and b-axis length. In conclusion, horiite has a new crystal structure with new ideal formula in the bafertisite group.

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