The crystal structure of magnesiorowlandite-(Y) and yftisite-(Y) from Komono, Mie Prefecture, Japan

Abstract

The crystal structures of magnesiorowlandite-(Y) [(Y,Ln)₄(Mg,Fe)Si₄O₁₂F₂] and yftisite-(Y) [(Y,Ln)₄(Ti,Al)(SiO₄)₂O[F(OH)]₆] were solved and refined with single crystal XRD data. In magnesiorowlandite-(Y), the Si₂O₇ group, together with (Mg,Fe)O₄F₂ octahedron, connects the 7-coordinate and 8-coordinate REEs polyhedra to form the 3-dimensional structure. In yftisite-(Y), the infinite columns of SiO₄ tetrahedra and (Ti,Al)(O,F)₆ octahedra are linked by the 7-coordinate and 8-coordinate REEs. Yftisite-(Y) can be revalidated as in independent mineral species with these new data, although this mineral has been discredited by the IMA commission in 1987 because of incomplete chemical analysis of the original description.