Abstract
Rhodonite has space group P[unk] and unit-cell parameters a = 7.682 Å, b = 11.818 Å, c = 6.707 Å, α = 92.355°, β = 93.948°, and γ = 105.665°. A trial structure determined through application of the minimum function to the Patterson function, P(xyz), was improved and refined with Fourier syntheses and least squares.
Planes containing octahedrally coordinated cations alternate with planes of tetrahedrally coordinated Si ions between planes of approximately close-packed oxygen ions. Tetrahedra are linked to form chains with a repeat unit of five tetrahedra. Octahedrally coordinated cations occupy five general equipoints, with Ca preferentially distributed in one position, and Mg and Fe in another. Octahedra share edges to form bands extending parallel to the silica chains and separated by a rift of unoccupied octahedrally coordinated sites.
