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

4:00 PM - 4:15 PM JST(7:00 AM - 7:15 AM UTC)

[R1-02] Amaterasuite, a new mineral in jadeitite from Osayama, Okayama Prefecture, Japan

*Daisuke HAMANE¹, Mariko Nagashima², Yuki Mori³, Masayuki Ohnishi, Norimasa Shimobayashi⁴, Takashi Matsumoto⁵, Mitsuo Tanabe (1. Univ. of Tokyo, 2. Yamaguchi Univ. Sci., 3. JASRI, 4. Kyoto Univ. Sci., 5. Rigaku)

Keywords:

Amaterasuite,New mineral,Jadeitite,Osayama

Amaterasuite is a new mineral found in jadeitite, a representative stone of Japan, and was thus named after Amaterasu Omikami, one of the most important goddesses in Japanese mythology, as a tribute to Japanese stone culture. The new mineral was found in the Osayama mountain area, Niimi City, Okayama Prefecture, Japan. Amaterasuite appears as bundles consisting of needle- to plate-shaped crystals as large as 150 μm around rutile. The empirical formula is (Sr_3.32Ba_0.64)_Σ3.96(Ti_5.73Fe_0.16Nb_0.02)_Σ5.91Si_4.15O₂₃(OH)_0.95Cl_1.05; thus, its ideal formula is Sr₄Ti₆Si₄O₂₃(OH)Cl. The unit-cell parameters refined by powder X-ray diffraction are a = 5.85558(2) Å, b = 20.43960(8) Å, c = 33.28240(12) Å, and V = 3983.43(3) ų (Z = 8) in the orthorhombic Fddd space group. The structure of amaterasuite was fully identified as amaterasuite-4O, which is characterized by its dual nature, encapsulating two types (A and B) within a unit cell. The occupancy rates of the A and B types were estimated to be ~85% and ~15%, respectively. The refined site occupancy at the SrA site indicates a strong site preference for Sr, similar to the preferential site occupancies in synthetic titanosilicate compounds by Cadoni et al. (2008).

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