Silicon

Silicon is commonly classified as a metalloid, with properties between those of metals and nonmetals. This hard, brittle solid has a blue-gray metallic shine. It is the second most abundant element in Earth's crust after oxygen, but occurs mainly in compounds rather than as the pure element. These include silica, or silicon dioxide, found in quartz, and silicate minerals that make up many rocks. Industry obtains silicon by heating silica with carbon in electric furnaces, then purifies it further for electronics. Silicon is a semiconductor: its ability to carry electric current can be controlled by adding tiny amounts of other elements. This makes it useful in computer chips and solar cells. Its compound silica is also a major ingredient in ordinary glass.