| Abstract |
A vanadium garnet has been found from a manganese ore deposit of the Yamato mine in the Palaeozoic formation of Amami Ōshima Island. The garnet forms dull greenish aggregates impregnated in the rhodon...ite ore and associates with some rare minerals, such as roscoelite and “haradaite.” The garnet is yellowish green in thin section, usually isotropic. Refractive index, 1.855±0.005. Specific gravity, 3.91 at 18℃. Cell dimension, a_0=11.9743Å. Chemical composition: SiO_2 35.76, TiO_2 0.11, Al_2O_3 1.96, Fe_2O_3 1.13, V_2O_3 24.90, FeO tr., MnO 15.92, MgO 0.08, CaO 19.28, Na_2O 0.25, K_2O 0.04, H_2O^+ 0.54, H_2O^- 0.10, total 100.07 wt. %. Chemical formula is (Ca_<1.79>Mn_<1.17>Mg_<0.01>Na_<0.04>)_<3.01>(V'''_<1.72>Al'''_<0.02>Fe'''_<0.07>Ti_<0.01>)_<2.00>Si_<3.00>O_<12.00>. The Yamato garnet is composed of two kinds of garnet molecule Mn_3V_2Si_3O_<12> and Ca_3V_2Si_3O_<12>. It reveals the existence of a new manganese-calcium series in vanadium garnet group.show more
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15_01_p073