The term “hydrothermal mineralization” is known as “hydrothermal precipitation,” “hydrothermal crystal growth,” or as “hydrothermal synthesis,” has its origins in the geological field. The term “hydrothermal mineralization” refers to heterogeneous reactions carried out in an aqueous solvent, sometimes with the presence of a mineralizer, under high temperature and pressure conditions. The most important thermodynamic parameter in precipitation processes is the solubility, i.e., the maximum amount of a solute that can be dissolved in a solvent. The first applications of hydrothermal mineralization, during the past century, were mainly directed toward the synthesis of large-size bulk crystals of compounds of interest, carried out at very high temperatures and pressures in order to favor crystal growth over nucleation. Hydroxyapatite, is the most stable calcium phosphate mineral under neutral to alkaline conditions. Antimony is industrially used as a fire retardant, or in the fabrication of ceramics and other advanced materials. Boron is an important micronutrient for both plants and humans.