Looking at the NixCo1-x-struvite precursors, even low amounts of Ni could prevent the decomposition to the M-dittmarite compound at room temperature. The heated products of the NixCo1-x-solid solutions transform to a single amorphous phase, to single crystalline Mdittmarite or a two-phase mixture of both depending on the Ni# (ESI: Figure ). High Ni content is favorable for the formation of the amorphous phase, while high Co content leads to the recrystallization of M-dittmarite. Polyamorphism, the occurrence of multiple phases with a different amorphous structure, cannot be completely excluded, especially in the heated NixCo1-x-mixtures, based on the XAS signal. But even if several amorphous phases are present in considerable amounts, they appear to have a similar short-range order. In this regard, the Fourier transformed spectra in R-space demonstrate no peak splitting.