A chemical element, In, atomic number 49, a member of group 13 and the fifth period of the periodic table. Indium has a relative atomic weight of 114.82. Indium occurs in the Earth's crust to the extent of about 0.000001% and is normally found in concentrations of 0.1% or less. It is widely distributed in many ores and minerals but is largely recovered from the flue dusts and residues of zinc-processing operations.