Element Indium, In, Poor Metal

In 1863 Ferdinand Reich, the head of Freiberg Mining academy Metallurgical laboratory with his assistant Hieronymus Theodor Richter were engaged in spectroscopic analysis of polymetallic ores and "earths" recovered in Freiberg area (Ore Mountains region), in search of thallium, which was discovered not long before that, in 1861 by English and French scientists. In spectrum of a sphalerite specimen they noticed two bright-blue lines of an unknown element. Soon they succeeded to extract a small amount of the new element, which they named indium, after the indigo line in its atomic spectrum. Richter went on to isolate the metal in 1867. In 1869 - 1871 Mendeleev, had measured the specific heat capacity and investigated the chemical properties of indium. He came to conclusion that his atomic weight should be approximately 114, and its capacity to form alums means that this element belongs to Aluminium subgroup. Later Henry Moseley confirmed all Mendeleev's conclusions.

Indium is a typical rare element by its abundance and a typical trace element by its dispersion. Its crustal abundance is 1.4x10^-5%. Around 10 indium own minerals are known. Minerals in which indium is an essential element are very rare - indeed only three have been observed: dzahlindite In(OH)₃, indite FeIn₂S₄ and roquesite CuInS₂ (Genkin and Muraveva 1964). They do not have any commercial importance. Indium's ionic radius is close to those of more wide-spread elements (Fe, Zn, Mn, Sn, Mg, Pb etc). Indium may embed into their crystal grids. Nevertheless such minerals are very rare; their total quantity hardly exceeds several thousands of a percent. Minerals with 0.05-1% Indium is extremely small. Cylindrite Pb₃Sn₄Sb₂S₁₄ (0.1-1% In) and franckeite (up to 0.1% Indium) as well as sphalerite ZnS (0.1-1% Indium), chalcopyrite CuFeS₂ (0.05-0.1% Indium) and bornite Cu₃FeS₃ (0.01-0.05% Indium) are the most well-known among them. Small amounts of Indium are found in black coals, petroleum from some deposits (up to 2.2x10^-6% Indium), also in seawater ((0.02-7)x10^-10% Indium) and in rainwater ((0.002-2)x10^-7%). Indium abundance in Universe is estimated to be 3x10^-10%mass. or 3x10^-12% at.

Exact amount of Indium global reserves are unknown. According to United States Geological Surveys, in 2004 the capacity of Indium developed pool contained 2.5x10³ tons of Indium.