Аннотация:Single crystals of CsMn(H2O)6(PO4) were synthesized under medium-temperature hydrothermal conditions. The new compound was established to be the first Mn member and the second hexagonal modification in the struvite morphotropic series of phosphates and arsenates, with hydrogen bonding between the main structural units.Crystal chemical analysis of the new phosphate in comparison with other members of the family revealed general features for the struvite morphotropic series, AM(H2O)6(XO4), where A = K, NH4, Rb, H2O, Cs, and Tl, M = Mn, Fe, Co, Ni, and Mg, and X = P, As.