Germanium

Germanium is a shiny, grayish-white metalloid: it looks metallic but is brittle and shares chemical properties with silicon. It is a semiconductor, a material whose ability to carry electric current can be controlled. Germanium occurs in small amounts in minerals, especially some zinc ores such as sphalerite, and in certain coal deposits. Industry recovers it mainly as a by-product of zinc processing, and also from the ash of germanium-rich coal. Its compounds are separated and purified before being converted into the element. Germanium lets infrared radiation pass through, making it useful for lenses in thermal imaging cameras. Its compound germanium dioxide is added to the glass cores of optical fibers to help guide light signals.