Crystal structure of suzukiite from the Mogurazawa mine, Gunma Prefecture, Japan

摘要

Suzukiite from the Mogurazawa mine, Gunma Prefecture, Japan exhibits orthorhombic space group Cmcm, a = 5.3546(16), b = 15.249(5), c = 7.094(2) A, Z = 2. Electron microprobe analyses yielded the empirical formula (Ba_(0.977)Sr_(0.027))_(Σ1.004)V_(1.013)Si_(1.985)O_7. The crystal structure was refined to R = 0.0211. The crystal structure of suzukiite comprises BaO_(11) polyhedra, SiO_4 tetrahedra, and VO_5 square pyramids. The Si_4O_(12) chain runs parallel to the c axis, and the VO_5 square pyramids link the chains to form a layer parallel to the ac plane. Ba atoms are located in the interlayer region and stack alternatively with the silicate-vanadate layers. The coordination of Ba in suzukiite is considerably distorted owing to the tight framework of the silicate-vanadate layer. The b length of the unit cell of suzukiite is larger than that of haradaite, the Sr analogue, whereas the a and c lengths show no remarkable difference.