metallic element, 1864, Modern Latin, from indicum "indigo" (see indigo) + chemical name element -ium. So called for its spectral lines. Ferdinand Reich (1799-1882), professor of physics at Freiberg, isolated it while analyzing local zinc ores in 1863 and identified it as a new element by the two dark blue lines in its spectrum, which did not correspond to any known element. The discovery had to be observed by his assistant, Theodor Richter, because Reich was color-blind.
updated on November 22, 2015