17
Germanium [Ge, 32]

17.1 INTRODUCTION
Germanium (Ge) is a metalloid of the group 14 in the periodic table of elements.
Its concentration in the Earth’s crust averages 1.5 mg/kg. Its similar contents are
present in igneous rocks. In argillaceous sediments, Ge ranges from 1 to 2.5 mg/kg,
and in calcareous rocks is <0.3 mg/kg. Its geochemical behavior is similar to
Si and Sn, the neighboring elements of the same group. Hard coal contains Ge
within the range 1–780 mg/kg, and fly ash contains 6–250 mg/kg.
Preferable Ge oxidation state is +4, and may also be +2. It exhibits various properties such as lithophilic, siderophilic, and chalcophilic, and easily substitutes Si
in silicate minerals, and forms complexes with oxygen. Its common minerals are
germanite, Cu 2 (Ge,Fe)S 4 , and argyrodite, Ag 8 GeS 6 . It is likely to be associated with
Pb–Zn–Cu sulfide ores.
During weathering, Ge is easily mobilized, mainly as Ge(OH) 2 , and is readily
absorbed from aquatic systems, by clay minerals, Fe hydroxides, and organic matter (OM). This might explain its elevated concentrations in several coals, where it is
often associated with the occurrence of sphalerite, (Zn,Fe)S (Font et al. 2005).
World mine Ge production (rounded) in 2010 was 120 kt, of which China produced 80; Russia produced 5; and the United States produced 4.62 (USGS 2011).
Generally, it is a by-product obtained from smelter dusts of the Zn production
and from Pb–Zn–Cu sulfide ores. Now it is mined primarily from sphalerite,
and also it is recovered from Ag, Au, and Cu ores. Significant amounts of Ge are
contained in ash and flue dust generated in the combustion of certain coals for
electric power, and its recovery by means of flotation is highly effective, at 100%
of its contents. The Ge emission from coal burning is calculated globally at about
700 t/yr.
Germanium is an important commodity in several manufacturing sectors, such
as fiber-optic and infrared optics. It is also used for polymerization catalysts, and
in the production of nanowires and organometallic compounds. Its most important use is in the multijunction solar cells for satellites, and terrestrial-based solar
concentrator systems and infrared devices. In some memory chips, an alloy of Sb,
Ge, and Ti is applied. The use of GeO 2 in catalysts for the polyester (polyethylene terephthalate) production is declined. Gallium organic compounds are used
in the chemotherapy, as a strong pain reliever, especially in the Asian medicine
(Moskalyk 2004). Some complexed organic Ge compounds are being presently
investigated as possible pharmaceuticals, al though none have yet been proven
successful.
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