The scarcity of these metals: a challenge for the societies of tomorrow
Many metals are essential for21st-century technologies, including numerous “green” technologies such as batteries, solar panels,wind turbine magnets, and fiber optics. Some of these metals are considered “critical” because their supply is uncertain.
Alexandre Cugerone, University of Montpellier; Bénédicte Cenki-Tok, University of Montpellier and Emilien OLIOT, University of Montpellier
We are seeking to understand how certain critical metals concentrate in the Earth’s crust so that they can be extracted more easily, with the aim of inspiring new methods for the exploration and environmentally responsible recovery of certain wastes from past mining operations, particularly in France and Europe.
In fact, these critical metals (rare earth elements, cobalt, lithium, platinum group metals, germanium, etc.) are found either in minute quantities, scattered throughout base metals such as zinc and copper, or, in some cases, in highly concentrated minerals smaller than one-tenth of a millimeter. To fully understand this fundamental difference using an everyday example, consider a single chocolate cake: one with melted chocolate evenly distributed throughout the batter, and another with chocolate chips. Which form of chocolate is easiest for food lovers to get their hands on once the cake is baked? The chocolate chips, of course! The principle is the same in our study: it is easier to extract critical metals from small, concentrated minerals (our chocolate chips) rather than from those scattered throughout the base ore (the melted chocolate in the cake batter).
The Challenge of Securing "Next-Generation" Metals
Many natural metallic substances are still mined today, such as base metals and ferrous metals (copper, zinc, iron, manganese, etc.) or precious metals (gold, silver, platinum, etc.). “Technological metals, ” such as “lithium, ” “rare earth elements, ” tungsten, or other rare metals (germanium, gallium, indium), have become indispensable due to the digital revolution and are also crucial for the development of “green technologies.”
See also:
Why do we talk about the "criticality" of materials?
If we continue to mine these critical metals at the current rate and under these conditions—especially since most of them are considered critical—we could face a supply crisis and significant environmental impacts.
Author provided
Among these critical metals, the elements in the “rare earth” group, as well as lithium and cobalt, are essential for new automotive and computer technologies. Tungsten is valuable in certain aerospace alloys. Rare metals such as gallium, germanium, and indium are essential for the manufacture of fiber optics, solar panels, and electronic systems, and could improve the performance of lithium-ion batteries. These metals are primarily extracted as byproducts of zinc sulfide, in which they are diluted.
Where are rare metals concentrated, and how can we extract them more effectively?
Our study shows that rare metals such as germanium, gallium, and indium can exist in minute quantities, dispersed within crystals of base metals, but also within small, hyperconcentrated host minerals. We have demonstrated that the deformation of zinc sulfide ore, occurring simultaneously with the formation of mountain ranges, promotes the re-concentration of germanium into hyperconcentrated minerals (our “chocolate chips”) at the heart of mountain ranges, in this case, the Pyrenees.
Consequently, it becomes very worthwhile to explore mining sites where deformation caused by natural geological processes has acted as a "natural concentrator" for rare metals.
Author provided
This may apply to the rare metals listed, but could also hold true for other technological metals, such as the rare earth elements. Many mining sites were historically exploited solely for their base metals, and today, many of the tailings piles or mining residues from this past exploitation could be put to use. There could be significant concentrations of rare metals in these mine tailings, particularly in the Pyrenees, the Massif Central, but also in the Alps, or in the Scandinavian mountains of northern Europe, and they may constitute potential rare metal resources.
Furthermore, when a rare metal, such as germanium, is dispersed throughout the ore,extraction is complex, requires extensive hydrometallurgical processes, and results in significant losses during extraction. On the other hand, if these rare metals are concentrated (like chocolate chips in a cake) within small minerals, their separation using various mechanical processes could be improved and better utilized, whether at current mining sites or in certain tailings piles or mining waste.
Our study proposes rapid, low-cost techniques for characterizing the mineralogical texture (crystal size and shape) and chemistry of rock samples, as well as for locating rare metals within them and assessing their concentration and potential for extraction.
Can we break free from our near-total dependence on Europe for metal resources?
Currently, the global market for rare metals (gallium, germanium, indium) as well as rare earth elements is dominated by China. Europe is almost entirely dependent on Asia, the Americas, and Africa. But what would be the economic consequences for our industries if a crisis in the supply of mineral resources—particularly “technological metals”—were to arise between our countries or continents?
European Commission
Social and environmental impacts
It is particularly paradoxical that we import the metal resources needed for our21st-century technologies—some of which are strongly associated with “green” or “renewable” initiatives—from distant countries with lax or nonexistent environmental regulations governing mining operations.
See also:
Rare Earths: Our Heavy Reliance on China (and How to Break Free)
Wouldn’t one solution be to extract our metals—for example, from certain mine tailings piles in Europe that are rich in critical metals—in ways that are eco-friendly and environmentally responsible? We need to better understand how critical minerals form and concentrate from a chemical and geological perspective, which could make it possible to revisit certain abandoned mines and repurpose their tailings piles.
Alexandre Cugerone, Ph.D. in Geosciences – Mining Geology/Metallogeny – Geosciences Montpellier, University of Montpellier; Bénédicte Cenki-Tok, Associate Professor at the University of Montpellier, EU H2020 MSCA visiting researcher at the University of Sydney, University of Montpellier and Emilien OLIOT, Assistant Professor of Earth Sciences, University of Montpellier
This article is republished from The Conversation under a Creative Commons license. Readthe original article.