No commodity gets as many column inches proportionate to its economic importance as rare earths. The total global rare earth market is worth some $4 billion. In comparison, how often do you read in a newspaper about titanium dioxide pigment ($19 billion), potash ($63 billion) or refractory minerals ($21 billion)?

Something about rare earths captures the media's attention. Journalists who wouldn't know a placer deposit from an ion-adsorption clay deposit are always ready to write breathlessly about the latest "world's biggest rare earth deposit" every few months. Meanwhile, progress on new rare earth projects remains grindingly slow, and investors are growing increasingly wary of the sector. 

As chemical nomenclature goes, "rare earths" has a certain ring to it. But the name is highly misleading, for a host of reasons. It's high time the industry abandoned this term, rooted in outdated science, confusing to outsiders, and which raises pitfalls even for seasoned investors. 

Neither rare nor earths

If you know anything about critical minerals, you'll know rare earths aren't actually rare. Cerium, the most abundant rare earth, is more common than copper in the earth's crust, while even the rarest of the rare earth metals are hundreds of times more abundant than gold. The one exception to that is promethium, an unstable lanthanide that barely exists in nature, and is sourced from nuclear reactors.

But the term "earth" is hardly less confusing. Rather than referring simply to a material dug up from the ground, it's actually a relic of the ancient theory of the four elements; earth, water, air and fire.

In the early modern period, chemists called substances like alumina and magnesia, that were unreactive to any amount of heat, and were also insoluble in water "earths", believing them to be a pure expression of the element of earth.

This same idea gave its name to the alkaline earth metals like magnesium. 

When the Finnish chemist Johannes Gadolin received a sample of a heavy black ore from Ytterby in Sweden in 1792, he dubbed the unfamiliar mineral a "rare earth".

But within a few decades of that discovery, it had become clear to science that the so-called "earths" were, in fact, oxides of metals, meaning the terminology was outdated shortly after it was coined. 

Geopolitical implications

This would all be an entertaining etymological anomaly, were it not for the fact that it is so widely misunderstood.

Media and politicians repeatedly step on the same rake by assuming that rare earths are synonymous with anything in the earth that is rare. The confusion between rare earths and other critical metals like lithium and cobalt is one that crops up constantly. 

The distinction is not mere pedantry. The unravelling diplomatic situation between Ukraine and the US seems to have been badly affected by the former country's refusal to cede control of its mineral assets. US President Donald Trump has repeatedly referred to rare earths (of which Ukraine produces none) in contexts where he almost certainly means critical minerals or just minerals in general. 

A similar confusion may be driving the president's stated ambition of absorbing Greenland and its mineral deposits into the US. 

More than just lanthanides

If politicians and journalists won't do their homework, why is this any concern for miners? Well, even within the industry, there is plenty of scope for confusion. There are seventeen rare earths, although, as discussed, you will never find promethium in a rare earth mine. 

But that aside, the rare earths comprise a slightly random collection of fifteen lanthanides, along with scandium and yttrium. The inclusion of the latter two in the rare earth group is something of an accident of history. They were discovered alongside the lanthanides and share similar chemical properties but are in some ways quite separate. 

The biggest outlier is scandium. Most scandium is not mined alongside other rare earths.

It is produced, in small quantities, as a byproduct or from the processing of tailings from iron ore, uranium or nickel production. Scandium also has very different demand drivers. Although some finds its way into electronic and lighting applications alongside other rare earths, the biggest end use is as an aluminium alloy, and in solid oxide fuel cells, making for a metal that has a completely different supply chain from start to finish. 

Yttrium has a closer link to the lanthanides, being mostly produced from the same mines and used in the same end markets.

But its inclusion among the rare earths is also a common trap for investors. Yttrium has conventionally been grouped among the heavy rare earths, as it is sourced from the same ion-adsorption clays in southern China and Myanmar.

But it is much cheaper. The USGS currently reports the yttrium price at just $8/kg, barely more than junk lanthanides like cerium and lanthanum. Meanwhile, heavy lanthanides like dysprosium and europium run to hundreds of dollars a kilo.

This means that a rare earth junior can, in good faith, market a "heavy rare earth project" that, on closer examination, turns out to be mostly comprised of low-value and essentially unmarketable yttrium.

Time for a name change

So what should we call them? In the current market, the best term might be "magnet metals".

Only five of the fourteen mined lanthanides - neodymium, praseodymium, terbium, samarium and dysprosium - regularly find their way into magnets. But this represents the fastest-growing demand driver and, crucially, is the only market that could currently justify a new mine being built outside of China. 

But pinning the sector on only one application is likely to lead to more confusion down the line.

The best solution is probably the simplest: we should just call them lanthanides and leave yttrium and scandium for the later pages of the prospectus - if they warrant a mention at all.

Of course, this would make for a much less sexy investment pitch. But that might be for the best in mining's most overhyped and underperforming sector.