The mechanisms by which amorphous intermediates transform into crystalline materials are still poorly understood. Here we attempt to illuminate the formation of an amorphous precursor by investigating the crystallization process of zinc phosphate hydrate. This work shows that amorphous zinc phosphate (AZP) nanoparticles precipitate from aqueous solutions prior to the crystalline hopeite phase at low concentrations and in the absence of additives at room temperature. AZP nanoparticles are thermally stable against crystallization even at 450 °C, but they crystallize rapidly in the presence of water if the reaction is not interrupted. X-ray powder diffraction (PXRD) with high-energy synchrotron radiation, scanning and transmission electron microscopy (SEM, TEM), selected area electron diffraction (SAED), and small-angle X-ray scattering (SAXS) showed the particle size (≈ 20 nm) and confirmed the non-crystallinity of the nano-particle intermediates. Energy dispersive X-ray (EDX), infrared (IR), and Raman spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), and optical emission spectrometry (ICP-OES) as well as thermal analysis were used for further compositional characterization of the as synthesized nanomaterial. 1H solid-state NMR allowed the quantification of the hydrogen content, while an analysis of 31P{1H} C-REDOR spectra permitted a dynamic and structural analysis of the crystallization pathway to hopeite.