Depending on the heat treatment schedule in a SiO2-Al2O3-CaO-P2O5-K2O-F glass, apatite of either needle like to isometric shape is shown to crystallise. The combined application of 31P MAS NMR spectrometry and transmission electron microscopy in conjunction with energy-dispersive X-ray spectrometry proves the degree of dissolution of liquid liquid phase separation droplets present in the casted glass to have a major influence on the morphology of apatite crystals. Since at 800 degrees C, a smaller number of droplets become dissolved as compared with a treatment at 1200 degrees C (instead they are converted into apatite), the super-saturation of the glass responsible for the formation of apatite is lower at 800 degrees C. Together with kinetic factors affecting the growth of apatite crystals (viscosity, diffusion), the different Ca/P-ratio is responsible for the two apatite morphologies observed.
