Quartz is piezoelectric: squeeze a crystal and a voltage appears across it, apply a voltage and it flexes. A sliver cut to vibrate 32,768 times a second is the heart of every quartz clock. In the structure every silicon sits in a tetrahedron of four oxygens, and the tetrahedra share corners in helices that wind the same way through the whole crystal, so a crystal is either left- or right-handed.
Research Elements Compound · SiO2 One unit cell, the smallest block that repeats in every direction to build the whole crystal. Atoms on its faces, edges and corners are shared with the neighboring cells, and oxygens just outside it are drawn so every silicon has its four. Farther atoms are drawn fainter. Atom positions from the Crystallography Open Database entry 9005017 (Kihara, K., 1990). The most common mineral at the Earth's surface after the feldspars: a main ingredient of granite, gneiss and sandstone, the grains of most beaches and dunes, and the veins that carry gold. Clear crystals come from Minas Gerais in Brazil, the Ouachita Mountains of Arkansas and the Swiss Alps. Amethyst, citrine, smoky quartz, rose quartz, agate and flint are all quartz. Mostly as silica sand, dug or dredged from sand deposits and sandstone quarries, then washed and screened for glassmaking, foundry molds and fracking proppant. High-purity quartz for the crucibles that silicon ingots are grown in comes from pegmatites at Spruce Pine, North Carolina, crushed and cleaned by flotation and acid leaching. The flawless crystals in watches and radios are not mined at all but grown in autoclaves from dissolved quartz.Quartz
Elements
Crystal structure
Cell: a = b = 4.9137 Å, c = 5.4047 Å, angles 90°, 90° and 120°
Space group: P 32 2 1Where it's found
How it's mined
Notes