Crystal structure of babingtonite

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Abstract
Babingtonite, Ca2(Fe,Mn,Mg)FeHSi5O15, from the Yakuki mine, Japan, has triclinic space group P[unk] and unit-cell constants a = 7.509 ± 0.019 Å, b = 11.697 ± 0, 028 Å, c = 6.719 ± 0.017 ±, α = 91.433 ± 0.041°, β = 93.886 ± 0.030°, γ = 104.255 ± 0.029°, and Z = 2. Three-dimensional intensities were collected with the 2θ scan method and by using Zr-filtered MoKα. radiation. The structure was determined by solving three-dimensional Patterson maps with the minimum-function method. The final least-squares refinement for isotropic temperature factors, using 3265 reflections, gave R = 0.0612.The structure consists of two single chains of silica tetrahedra, containing five tetrahedra per repeat unit, running parallel to the [110] zone and connected by Fe,Mn,Mg octahedra. Ca atoms occupy the large openings existing between the tetrahedral chains and the octahedra, and form irregular polyhedra each with eight oxygen atoms. The average distance from Si to the nonbridging oxygen atoms is 1.614 Å and from Si to bridging oxygen atoms is 1.652 Å. The range of Fe2+–O distances is between 2.066 and 2.239 Å; of Fe3+–O, between 1.934 and 2.206 Å; and of Ca–O between 2.287 and 3.084 Å. The structure of babingtonite distinctly resembles that of rhodonite.

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