Hafnon
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Hafnon is a hafnium nesosilicate mineral, chemical formula SiO₄ or 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... Wikipedia
Density: 6.97
Common impurities: Often zoned with zircon. Forms part of zircon-hafnon series
Crystal class: Ditetragonal Dipyramidal (4/mmm); H-M symbol: (4/m 2/m 2/m)
Crystal habit: Euhedral to irregular crystals
Crystal system: Tetragonal
Mohs scale hardness: 7.5
Optical properties: Uniaxial (+)