1) Many watches and clocks keep time because a battery sends an electric current through a tiny piece of quartz, which vibrates 32 768 times per second. It's called the piezoelectric effect.
2) Quartz is also melted and then pulled into thin fibres that become fibre optics for high speed internet. The fibres have a quality called 'total internal reflection', which means that light stays inside the fibre rather than reflecting out of it.
3) Recent research suggests that it's the crystallisation of molten rock into quartz crystals close to the Earth's core that powers the Earth's magnetic field, which protects us from harmful cosmic rays.
4) Following an earthquake, quartz crystallises from molten rock inside regions where the Earth has torn, essentially fusing the two sides together again, almost like internal sutures. In effect, the formation of quartz crystals 'heals' the 'wound' in the Earth.