The Earth is estimated to contain about 0.1 parts per million (ppm) of indium.
Indium is produced mainly from residues generated during zinc ore processing, but it is also found in iron, lead, and copper ores.
Indium (chemical symbol In, atomic number 49) is a rare, soft, malleable and easily fusible metal.
Numerous other radioactive isotopes of indium are known, but most of them are extremely short-lived.
Indium was discovered by Ferdinand Reich and Hieronymous Theodor Richter in 1863, when they were testing zinc ores with a spectrograph in search of thallium.
The primary application of indium is to make thin, transparent electrodes from indium tin oxide for liquid crystal displays (LCDs).
Demand increased as the metal is used in LCDs and televisions, and supply decreased when a number of Chinese mining concerns stopped extracting indium from their zinc tailings.
Up until 1924, there was only about one gram of isolated indium on the planet.
The amount of indium consumed is largely a function of worldwide LCD production.
Pure indium in metallic form is considered nontoxic by most sources.
Several indium compounds are useful as semiconductors, and the oxide is good for making electroluminescent panels.
Indium is a very soft, silvery white metal, with a bright luster.
One unusual property of indium is that its most common isotope, 115In, is slightly radioactive—it decays very slowly by beta emission to tin.
The first large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II.