Indium is a chemical element with chemical symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to aluminium or gallium. Zinc ores are the primary source of indium. It is named for the indigo blue line in its spectrum that was the first indication of its existence in ores, as a new and unknown element.
Indium is an expensive by-product of lead and zinc mining. Indium tin oxide has a rare ability to be able to conduct an electrical current while also being optically transparent like glass, making it the best candidate for touch-control on modern smartphones.
Indium reserves are running low, current estimates show that reserves will run out in 13 years at the current rate, and alternatives are now being investigated - the successor most likely to be carbon nanotubes.