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.
Hafnon occurs as transparent red to red orange tetragonal crystals with a hardness of 7.5.
Hafnon occurs naturally in tantalum-bearing granite pegmatites in the Zambezia district, Mozambique and in weathered pegmatites at Mount Holland, Western Australia. It has also been reported from locations in Ontario, Quebec and Manitoba, Canada; North Carolina, United States; and in Zimbabwe.
References
Hafnon Wikipedia(Text) CC BY-SA