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

3:00 PM - 3:15 PM JST(6:00 AM - 6:15 AM UTC)

[R1-11] Hinokageite, a new mineral, from the Shimozuru mine, Miyazaki Prefecture, Japan

*Daisuke NISHIO-HAMANE¹, Mariko Nagashima², Yuki Mori³, Masayuki Ohnishi, Takahiro Tanaka, Hiroyuki Imai, Tatsumi Fukumoto (1. The University of Tokyo, 2. Yamaguchi Univ., 3. Univ. of Hyogo)

Keywords:

Hinokageite,Olivine structure

Hinokageite, ideally MnMg(SiO₄), is a new mineral species of the olivine group named after Hinokage Town, Miyazaki Prefecture, Japan. It occurs as a silicate mineral in alabandite-dominant manganese ore. The empirical formula is (Mn_1.212Mg_0.728Fe_0.061Ca_0.003)_Σ2.004Si_0.998O₄, whereas the crystal-structure analysis yielded the structural formula ^M2(Mn_0.904Mg_0.075Fe_0.020Ca_0.003)_Σ1.002^M1(Mg_0.653Mn_0.308Fe_0.041)_Σ1.002Si_0.998O₄, corresponding to the ideal formula MnMg(SiO₄). Although hinokageite is compositionally intermediate between forsterite, MgMg(SiO₄), and tephroite, MnMn(SiO₄), and appears to form a continuous solid solution with these end-members, mineral species are defined by their ideal formulas rather than by solid-solution relationships. The crystal-chemical data demonstrates that hinokageite possesses a distinct ideal formula, MnMg(SiO₄), which is not represented by either forsterite or tephroite. Therefore, hinokageite is approved as a separate mineral species within the olivine group.

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