aqueous solutions indicate the onset of crystallization around 100 °C. For q(H2O)A equal to 2.8, 2.2, the molar fractions of AOH are 26 and 31 %, respectively, which correspond to melting points below 100 °C, thus the KOH-based hydrofluxes yielding the hydroxyapatite are liquid at the crystallization onset. Two effects can be accounted for the evolution of anisotropy with the water content: a change in the solubility of the precursors, especially strontium as it is poorly soluble in strongly alkaline media, or a change in the energies of interfaces between the growing crystal and the hydroflux. Several analyses and experiments were then performed to decipher these two effects.