Hafnon is a hafnium silicate mineral, chemical formula (Hf,Zr)SiO₄ or (Hf,Zr,Th,U,Y)SiO₄. In natural zircon ZrSiO₄ part of the zirconium is replaced by the very similar hafnium and so natural zircon is never pure ZrSiO₄. A zircon with 100% hafnium substitution can be made synthetically and is hafnon.