Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms (SiO₂).
In nature, quartz is the second most abundant mineral in Earth's continental crust.
The term "quartz" also refers to:
1. Quartz watches - timepieces that use a quartz crystal oscillator
2. Quartz countertops - engineered stone surfaces
3. Quartz glass - a type of glass made from pure silica