pile of polycrystalline silicon 



Silicon is a chemical element which after oxygen is the most common element in the earth's crust.  A hard but brittle crystalline solid with a metallic lustre, it's sometimes confused with silica (silicon dioxide) which is a compound of silicon and oxygen.  Silicon should not be confused with silicone which is a synthetic substance that's a flexible rubber-like plastic.

China, Russia, the USA and Norway are the world's largest producers of silicon.   It is estimated that approximately twenty five per cent of the Earth's crust is made up of silicon.

Whilst silicon is used in the production of bricks and ceramics, it's also used to amplify or switch electrical currents and in computer chips because it's a semi conductor of electricity. 

The name Silicon Valley takes its name from the silicon that's used in computer chips.