Transition-metal-doped ZnO is considered a promising candidate for applications in spintronics. Here, we developed it novel and versatile synthetic route for obtaining impurity-free Mn-doped zinc oxide (Zn1-xMnxO) materials witha well-controlled content of Mn, with x up to 1.8 atomic %. Zn1-xMnxO is produced by thermal decomposition in reducing atmosphere of an inorganic precursor. Mn-doped hydrozincite. The materials are of high purity, as shown by detailed characterization. The obtained systems exhibit a spin-glass phase below 40 K together with a weak ferromagnetic ordering of the Mn dopants within the ZnO matrix.