What are rare earth minerals and why are they important?

US President Donald Trump said in February he wanted Ukraine to supply the country with rare earths in return for financially supporting Kyiv's war effort against Russia.

The remark appears to overlap with part of a war strategy, known as the "victory plan", that President Volodymyr Zelenskiy presented to Kyiv's allies, including Donald Trump, last year.

Among other things, the plan proposes reaching agreements with foreign partners to provide joint access to Ukraine's strategically valuable resources.

It was not immediately clear if Trump was referring to all types of critical minerals or just to rare earths. He said the United States was looking to do a deal with Ukraine for "their rare earths and other things".

Rare earths are a group of 17 metals used to make magnets that turn power into motion for electric vehicles, cell phones, missile systems and other electronics. There are no known substitutes.

China is the world's largest producer of rare earths and many other critical minerals.

Trump has also expressed interest in making Greenland, an autonomous territory of Denmark which also sits on large rare earth deposits, a part of the US since his re-election.

The US Geological Survey considers 50 minerals to be critical, including several types of rare earths, nickel and lithium.

Ukraine has deposits of 22 of the 34 minerals identified by the European Union as critical, according to economy ministry data. This includes industrial and construction materials, ferroalloy, precious and non-ferrous metals and some rare earth elements. Ukraine also has significant reserves of coal; however, most of them are now under the control of Russia in occupied territory.

Why are rare earths important?

The 17 silvery-white rare earth minerals are not uncommon in the earth's crust. But deposits that are economically viable are more difficult to find, and the real rarity comes in the complex process to separate them into the materials needed to produce permanent magnets used in a range of critical products.

China accounts for about 60% of global rare earth mine production, but its share jumps to 90% of processed rare earths and magnet output.

Below are the complex steps that rare earths must take to end up as magnets used in electric vehicles and wind turbines — the two main areas driving demand in coming years.

Mine

Ore is first extracted from an open pit or underground mine, crushed and moved to a plant, usually near to the mine site.

The ore contains a small percentage of rare earths, but other minerals are removed through flotation, magnetic or electrostatic processing to produce a mixed rare earth concentrate that often contains 60% to 70% rare earths.

Other operations produce a rare earth concentrate as a byproduct of mining waste or from other metals such as mineral sands or iron ore.

Radioactivity

Certain types of ore, such as monazite, have to undergo another step to remove radioactive thorium or uranium from the ore, often using acid.

Separation

One of the most difficult steps is separating the individual rare earths from each other. The technology was first developed after World War II in US government research laboratories.

Separation can be accomplished using ion-exchange technology. It can also be done using solvents such as ammonia, hydrochloric acids and sulphates, although some such chemicals produce toxic wastes that can cause cancer.

So-called light and heavy rare earths must go through different separation circuits where individual rare earths are extracted.

New more environmentally-friendly technologies are being developed, but they are not yet widely used.

Metals/alloys

Separated rare earth oxides are then transformed into rare earth metals by electrolysis.

The most widely used permanent magnets combine rare earths neodymium and praseodymium together with iron and boron, which are put in a vacuum induction furnace to form an alloy. Small amounts of rare earths dysprosium and terbium are often added to create more heat resistance in the magnet.

Magnets

The alloy ingots are broken down and jet-milled in a nitrogen and argon atmosphere to micron-sized powder, which goes through a high-temperature and pressure process called "sintering" before being pressed into magnets.