Indium is a chemical element, with symbol In and atomic number 49.

This metal is the eighth non-renewable resource set to disappear thanks to intensive exploitation by mankind. At the same time as gold and zinc.

Indium is a shiny grey, malleable and rare metal, found only in minute quantities in zinc mines. Its massive use in recent years, especially in LCD flat screens, has caused its price to shoot up from 70 $/kg in 2001 to 1000 $/kg in 2005. It will probably disappear at the same time as zinc, in 2025. Certain sources even talk of 2018. It would appear, though, that nanotechnological materials, such as graphene could replace it in the near future. So this won"t spell the end of flat screens.

Indium is used in several forms: indium selenide, InSe₂, indium- gallium nitride InGaN and copper indium diselenide, CuInSe₂. Research under way on solar cells comprising several layers: gallium-indium-phosphorus, gallium arsenide and germanium (GaInP-AsGa-Ge) appears to indicate that we could eventually obtain yields in excess of 30%.

Thin-layer solar cells

This type of photovoltaic cell has a lower yield (10-20%) but is much easier to manufacture in large sizes. The material used can be indium-tin oxide, a copper-indium-selenium (CuInSe₂) mixture or copper-indium-gallium-selenium.

Infra-red detectors

Indium arsenide up to 3.8 μm and indium antimonide (InSb) up to 5 μm.

Mechanics: seats for bushes and bearings.

The incorporation of indium into steel alloys greatly reduces surface friction and hence wastage of energy.

Glass coatings

Indium adheres strongly to glass and is used for its reflective, (clear yellow) colouring and electrically conductive properties. It is therefore used as a transparent electrode in liquid crystal screens, in the manufacture of mirrors and in certain types of laminated glass, when heating properties are required.

Low melting-point alloys.

Indium is used for certain welding applications, where the presence of lead is not acceptable. The alloy gallium-indium (76% - 24%) is liquid at ambient temperature and is used (experimentally) as a non-polluting substitute for mercury in liquid mirrors for telescopes.

Nuclear medicine

In nuclear medicine, indium-111, with its two gamma-emissions of 173 and 247 keV, is useful for carrying out certain examinations. For example, in scintigraphy, it is possible, using white blood cells labelled with indium-111, to locate active abdominal processes and recent infections (less than 2 weeks old). In association with certain pharmaceutical products, this radioactive isotope can serve to locate various neuro-endocrine tumours (insulinomas, gastrinomas, paragangliomas, carcinoid tumours, phaeochromocytome , etc). It is also useful in scinticisternography.

Link: http://environment.newscientist.com

Problems arising from the disappearance of indium will start to make themselves felt well before this fateful date.

Even if, thanks to advances in technology, we find new deposits by digging deeper and deeper into the Earth"s crust, this will afford us only a few years"reprieve and will not make a major impact on the situation.

Indium was created when a star exploded and the Sun and the Earth were formed from the debris, over five billion years ago.

You cannot produce it artificially and there is no substitute. The Moon and the asteroids do not contain the metal in an extractable form. And just imagine the energy it would take to bring some back from Mars or Venus!

There will still be recycling but demand, which will keep growing exponentially with the development of the emerging economies, will far outstrip supply.

Indium deposits are associated with those of zinc, copper and tin. Their geographical distribution is thus similar to that for these metals ores.

To learn more about indium, see: https://en.wikipedia.org/wiki/Indium

Translation Nicholas ROSE

Don"t miss reading Point of view by Michel Walter , a programme for the end of our civilisation of wastage.