What is the chemical formula of 'quartz'?

SiO₂

The correct answer is option 4. \(SiO_2\).

Quartz is a mineral composed of silicon dioxide \((SiO_2)\). It is one of the most abundant minerals in the Earth's crust and exists in many different forms and varieties. The chemical formula for quartz is \(SiO_2\), indicating that each silicon atom is bonded to two oxygen atoms. Therefore, option 4, \(SiO_2\), is the correct chemical formula for quartz.