Beschreibung:
<jats:p>The crystal structure of brackebuschite, ideally Pb<jats:sub>2</jats:sub>Mn<jats:sup>3+</jats:sup>(VO<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>(OH) [dilead(II) manganese(III) vanadate(V) hydroxide], was redetermined based on single-crystal X-ray diffraction data of a natural sample from the type locality Sierra de Cordoba, Argentina. Improving on previous results, anisotropic displacement parameters for all non-H atoms were refined and the H atom located, obtaining a significant improvement of accuracy and an unambiguous hydrogen-bonding scheme. Brackebuschite belongs to the brackebuschite group of minerals with general formula<jats:italic>A</jats:italic><jats:sub>2</jats:sub><jats:italic>M</jats:italic>(<jats:italic>T</jats:italic>1O<jats:sub>4</jats:sub>)(<jats:italic>T</jats:italic>2O<jats:sub>4</jats:sub>)(OH, H<jats:sub>2</jats:sub>O), with<jats:italic>A</jats:italic>= Pb<jats:sup>2+</jats:sup>, Ba, Ca, Sr;<jats:italic>M</jats:italic>= Cu<jats:sup>2+</jats:sup>, Zn, Fe<jats:sup>2+</jats:sup>, Fe<jats:sup>3+</jats:sup>, Mn<jats:sup>3+</jats:sup>, Al;<jats:italic>T</jats:italic>1 = As<jats:sup>5+</jats:sup>, P, V<jats:sup>5+</jats:sup>; and<jats:italic>T</jats:italic>2 = As<jats:sup>5+</jats:sup>, P, V<jats:sup>5+</jats:sup>, S<jats:sup>6+</jats:sup>. The crystal structure of brackebuschite is based on a cubic closest-packed array of O and Pb atoms with infinite chains of edge-sharing [Mn<jats:sup>3+</jats:sup>O<jats:sub>6</jats:sub>] octahedra located about inversion centres and decorated by two unique VO<jats:sub>4</jats:sub>tetrahedra (each located on a special position 2<jats:italic>e</jats:italic>, site symmetry<jats:italic>m</jats:italic>). One type of VO<jats:sub>4</jats:sub>tetrahedra is linked with the<jats:sup>1</jats:sup><jats:sub>∞</jats:sub>[MnO<jats:sub>4/2</jats:sub>O<jats:sub>2/1</jats:sub>] chain by one common vertex, alternating with H atoms along the chain, while the other type of VO<jats:sub>4</jats:sub>tetrahedra link two adjacent octahedra by sharing two vertices with them and thereby participating in the formation of a three-membered Mn<jats:sub>2</jats:sub>V ring between the central atoms. The<jats:sup>1</jats:sup><jats:sub>∞</jats:sub>[Mn<jats:sup>3+</jats:sup>(VO<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>OH] chains run parallel to [010] and are held together by two types of irregular [PbO<jats:sub><jats:italic>x</jats:italic></jats:sub>] polyhedra (<jats:italic>x</jats:italic>= 8, 11), both located on special position 2<jats:italic>e</jats:italic>(site symmetry<jats:italic>m</jats:italic>). The magnitude of the libration component of the O atoms of the<jats:sup>1</jats:sup><jats:sub>∞</jats:sub>[Mn<jats:sup>3+</jats:sup>(VO<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>OH] chain increases linearly with the distance from the centerline of the chain, indicating a significant twisting to and fro of the chain along [010]. The hydroxy group bridges one Pb<jats:sup>2+</jats:sup>cation with two Mn<jats:sup>3+</jats:sup>cations and forms an almost linear hydrogen bond with a vanadate group of a neighbouring chain. The O...O distance of this interaction determined from the structure refinement agrees well with Raman spectroscopic data.</jats:p>