The topic of rare earths has overwhelmingly made its way to the fore in recent years. Not that they were unknown before: the mineral ytterbium was discovered at the end of the 18th century. But in the last twenty years they have become known as “technological minerals” due to their very close bond with contemporary society, for which they have become fundamental: electronics and portability have changed the world. First of all, this is a specifically geological issue (just like fossil fuels): around fifteen elements (17 by definition) out of the 120 known, distributed at the bottom of the periodic table, characterised by structures and compositions that make them unique.
So why are they called rare?
Not because they are rare: in fact, the rarest is in any case more common than cadmium, and some are even more common that copper. With the exception of promethium, an artificial radioactive element, they are found in relatively high concentrations in the earth’s crust; for example, lanthanum, cerium, neodymium and yttrium are more common than lead or silver and even the two least common, thulium and lutetium, are around 200 times more common than gold. A handful of soil taken from your back garden will probably contain a little, perhaps a few parts per million. On the other hand, fairly large, concentrated deposits that make mining activities worthwhile are infrequent. We call them rare because they are highly dispersed in their minerals of origin, with very low concentrations, on average around 1%. This means that we have to excavate tonnes of rock to obtain appreciable amounts. These earths are also very expensive: 100 grams can cost between 400 and 20,000 dollars, mostly due to their extraction process. And their environmental impacts must also be taken into account in the overall cost.
Limited distribution of rare earths worldwide
They were first highlighted and enhanced in the United States, where the richest deposits were found, and subsequently in China. But they are also found in significant quantities in the so-called BRICS countries and in Vietnam. The geological origins of rare earths lie in the very-often ancient volcanic history of those regions of the earth. The largest manufacturers are Chinese, with 60% of global production, followed by the USA. The Bayan Obo mine in China (18 km long), is the world’s largest; this is an iron mine where subsequently rare earths were also found, and for this reason it has been dug out to full capacity. Currently it is calculated that, in the world, there are 120 million exploitable tonnes of rare earths, so subject to exhaustion, just like all other resources.
What counts in rare earths are their properties
Electrical and magnetic properties, which are hard to replace, at least for the time being: there are no synthesis processes that can replace them. Rare earths are used in smartphones, TVs, circuit boards, as well as semiconductors used to make, and therefore are fundamental for, photovoltaic panels and wind turbines: one gram for a smartphone, one kilo for an electric car, one tonne for a large wind tower. For example, a single industrial-sized wind turbine generator requires neodymium, praseodymium, dysprosium and terbium, used to create permanent-magnet generators, a key technology for direct-drive turbines, offering higher energy performance and lower running and maintenance costs. In this case, to free the wind turbines from dependence on these elements, some researchers have developed a different approach to electrical power transmission for generators, a new type of rotary electric contact freed from geological dependence.
Why we need them
Substantially, the ecological reconversion and energy transition are in great need of rare earths, the “green” world cannot do without them. This is particularly due to the fact that we use electrically powered tools and devices with large, multi-purpose screens. Along with many other elements, rare earths become indispensable: if, for example, we can’t find the latest video game console model in shops, it is because there is a rare earth sourcing crisis. Technology and development limits have a precise thermometer with rare earths and super-conductors: over 70% of rare earths are used in electronics. And then, geopolitics: China tends to snap up all the African regions containing rare earths. Without mentioning their use in military technologies, especially to build drones.
The environmental footprint of rare earths
Recycling rare earths is complex and, currently, we are able to recover only a very negligible amount, 1%. Many rare earths are found in the electronic equipment we throw away, and which are dismantled and recovered by hand in poor countries. On the other hand, the war and the rare earth crisis have led to the discovery of some new deposits. In Italy, some former antimony mines have been found to have some rare earth deposits. In Sweden and France, new deposits are being exploited. In Japan, some large deposits have been found in the sea, and could even double global production.
Obtaining a tonne of rare earths produces around 2000 tonnes of often toxic materials which bring major environmental problems. The mining of rare earths has a lower impact on deforestation, indeed much less than other mining activities, including hydrocarbons and coal, as well as on farming and zootechnical activities. Some elements also have other uses, and are sought out more than others: lithium, found above all in the Bolivian ‘salar’ (large salt lakes in the Andes), as well as in China, is used in medicine, as it calms the mind and cures intestinal conditions, and is fundamental for many types of batteries, especially to extend their life.
Mario Tozzi, the geologist
Born in Rome in 1959. A curious geologist. Graduated from the famous La Sapienza University, a PhD in Geology, First CNR Researcher, Chairman of the Appia Antica Park, Knight of the Republic. Populariser and TV presenter on RAI (Italian state TV) since 1996. Writer and columnist for La Stampa. Advisor to TCI and WWF. Tells stories of the Earth in monologues and live performances with singer-songwriters and actors.
