95% of earth crust is made up of silica and silicates. The incorrect statement regarding silica is

Kiesulghur is amorphous form of silica

Silica is resistant to most of the acids except HF

$Si - Si$ bonds are stronger than $Si – O - Si$ bonds and $Si{O}_2$ is unstable due to weak bonds of $Si – O – Si$

Quartz, cristobalite, tridymite are crystalline forms of silica