Indium is a metal element, atomic number 49, symbol In.
It is a grey, malleable metal similar in chemical properties to aluminium and gallium. It melts at a low temperature (156.60 °C). Its commonest isotope is very slightly radioactive (half life 4.41.1014 years) and the final product is tin.
It is found in zinc mines (which is where it was discovered in the 1860s) and also in iron, lead and copper mines. Since the Second Word War it has been used for making ball bearings for the aeronautics industry. Later it was used in electronics for producing transistors. Since the 1990s its main application, in the form of a tin oxide (ITO, Indium Tin Oxide), has been in flat liquid crystal screens (LCD, Liquid Crystal Display), where it is used for the transparent electrodes.
At the current rate of demand world stocks are considered to be close to exhaustion. There is little recycling but this is now developing.