Rietveld refinement of a natural cobaltian mansfieldite from synchrotron data

A structural refinement of a natural sample of a Co-bearing mansfieldite, AlAsO(4)·2H(2)O [aluminium orthoarsenate(V) dihydrate], has been performed based on synchrotron powder diffraction data, with 5% of the octa­hedral Al sites replaced by Co. Mansfieldite is the aluminium analogue and an isotype of the mineral scorodite (FeAsO(4)·2H(2)O), with which it forms a solid solution. The framework structure is based on AsO(4) tetra­hedra sharing their vertices with AlO(4)(H(2)O)(2) octa­hedra. Three of the four H atoms belonging to the two water mol­ecules in cis positions take part in O—H⋯O hydrogen bonding.