Display of silicon crystals.
© Science Museum / Science & Society Picture Library
Two single crystals in a display case together with a section showing a tendency to twinning. Silicon is the second most abundant element after oxygen, and makes up over a quarter of the earth's crust. The element is produced by the reduction of silica (SiO2) with carbon or calcium carbide (CaC2) in an electric furnace. Pure crystals of silicon are grown to be sliced into thin wafers which contain silicon chips for use in making integrated circuits in computers. Silicon can form synthetic polymers in combination with carbon, hydrogen and oxygen. These compounds known as silicones form fluids, greases, rubbers and resins, and have a wide variety of uses including adhesives, lubricants, paints and waterproofing agents.