3:00 PM - 3:15 PM
[R1-12] On the Fe2+-analogue of zemannite from Kawazu mine, Shizuoka Prefecture, Japan
Keywords:zemannite, kinichilite, Kawazu mine
The Kawazu Mine in Shimoda City, Shizuoka Prefecture, has been known as type locality of two new minerals, kawazulite (Bi2Te2Se) and kinichilite. In the original description of kinichilite, its chemical composition was reported as (Fe2+1.13Mg0.47Zn0.43Mn2+0.17)Σ2.20(Te2.97Se0.03)Σ3.00O9.00(H1.38Na0.22)Σ1.60・3.2H2O, and as Fe analogue of zemannite at that time. Later, however, crystal chemical study of zemannite revealed that its ideal formula is Mg0.5[ZnFe3+(TeO3)3]･4.5H2O, i.e., iron is not 2+ but 3+ and both Zn2+ and Fe3+ are essential. If the originally reported chemical composition of kinichilite is recalculated based on this find, it remains in the compositional range of zemannite. However, R. Miletich (1995), in his study of zemannite group minerals, also examined the "kinichilite" from the Kawazu mine and found that manganese was predominant as a divalent ion in most of the analyzed point. He considered it as kinichilite and redefined its ideal formula as Mg0.5[MnFe3+(TeO3)3]･4.5H2O. Here, we report Fe analogue of zemannite, in which divalent iron exceeds zinc, manganese and other divalent ions.
One of the collections of the National Museum of Nature and Science (NSM-M41022) was used in this study. Chemical analysis was performed using a scanning electron microscope (JEOL JSM-6610) equipped with an energy dispersive X-ray spectroscopic detector (EDS). Water content was estimated by the difference from 100% of the EDS analysis. Single crystal X-ray diffraction (SXRD) experiments were performed using a Rigaku Synergy Custom equipped with a rotating anode and a multilayer X-ray focusing mirror (VariMax).
The empirical formula obtained from the average of four analytical points is Mg0.40(Fe2+0.54Zn0.33Cu0.18Mn0.05)Σ1.10Fe3+1.00(Te2.92P0.06O9)・4.12H2O. The SXRD experiment gave the space group P63 (or P63/m) with lattice parameters a = 9.37765(11), c = 7.58379(9), V = 577.570(15). The refinement converged with reliability index R1 = 1.56% and it was confirmed to be isostructural with zemannite. Distribution of the channel cations and bond lengths of the framework M sites indicate symmetry lowering from P63/m to P63.
One of the collections of the National Museum of Nature and Science (NSM-M41022) was used in this study. Chemical analysis was performed using a scanning electron microscope (JEOL JSM-6610) equipped with an energy dispersive X-ray spectroscopic detector (EDS). Water content was estimated by the difference from 100% of the EDS analysis. Single crystal X-ray diffraction (SXRD) experiments were performed using a Rigaku Synergy Custom equipped with a rotating anode and a multilayer X-ray focusing mirror (VariMax).
The empirical formula obtained from the average of four analytical points is Mg0.40(Fe2+0.54Zn0.33Cu0.18Mn0.05)Σ1.10Fe3+1.00(Te2.92P0.06O9)・4.12H2O. The SXRD experiment gave the space group P63 (or P63/m) with lattice parameters a = 9.37765(11), c = 7.58379(9), V = 577.570(15). The refinement converged with reliability index R1 = 1.56% and it was confirmed to be isostructural with zemannite. Distribution of the channel cations and bond lengths of the framework M sites indicate symmetry lowering from P63/m to P63.