Roweite from the Fuka mine, Okayama Prefecture, Japan

Roweite occurs as reddish to dark brown granular crystals up to 0.8 mm across in crystalline limestone near gehlenite-spurrite skarns at the Fuka mine, Okayama Prefecture, Japan. It is closely associated with uralborite. Associated minerals include shimazakiite, frolovite, bultfonteinite, fluorite and calcite. An electron microprobe analysis of roweite gave an empirical formula Ca-2.006(Mn1.410Fe0.333Mg0.181Zn0.036Co0.004)(Sigma 1.964)B4.017O6.989 (OH)(6.011) based on O = 13. The unit cell parameters are a = 9.057(2), b = 13.335(3), c = 8.284(3) angstrom. The calculated density is 2.92 g cm(-3). The roweite from the Fuka mine was probably formed as a secondary mineral from calcium borates such as uralborite in a reaction with manganese-bearing late hydrothermal solution.