In the pure-metal system, we observed a progressive transformation from amorphous to crystalline compounds. Based on this finding, we assumed that the formed crystals were the thermodynamically favored phases i.e. Ni-or Co-struvite. However, the mixed NixCo1-x experiments showed the opposite. Here, amorphous precursors coexist with crystalline phases over a long period, while the first precipitated crystals are unstable and "consumed" by a later forming crystalline phase.