If you are thinking of investing in rare earth metals this article briefly explores the history of the commodity and summarises many of its industrial and consumer applications.
History of rare earth metals
The terms rare earths, rare earth metals and rare earth elements are often used interchangeably, but historically this is incorrect.
While rare earth metals and rare earth elements are synonymous and correctly refer to the metallic elements on the periodic table, what were originally called rare earths were, in fact, metal oxides as shown by Sir Humphry Davy in 1808.
In 1751 a Swedish mineralogist called Axel Fredrik Cronstedt came across a mineral now called cerite, in a Swedish quarry. Analysis indicated it was an iron aluminium silicate and so it was ignored for half a century.
Thirty-six years later in 1787, Lieutenant Carl Axel Arrhenius discovered gadolinite, a black mineral that used to be called ytterbite, in another Swedish quarry. At the time this was thought to contain tungsten though when analysed some years later it was found to contain a previously undiscovered oxide now called yttria.
Attention then turned to the Cronstedt mineral, which yielded the new oxide ceria. Subsequent analysis of this in 1839 showed it to be a mixture of pure ceria and another earth lanthana, which was subsequently shown to contain yet another earth called didymia.
The story continued for many years until in 1907 the sixteenth rare earth had been found. The seventeenth, polonium, was found in fission products in 1947.
Why are they called rare?
With the exception of promethium, rare earth metals are not rare despite their name. For example, Cerium is as abundant as copper, and even the rarest of the other rare earths, lutecium, and thulium, are more abundant than cadmium; and selenium and 400 times more abundant than gold.
So,why are they called rare? The main reason is that they are evenly distributed across the planet, and it is unusual to find them in large ore deposits, which means mining rare earths is not generally economically viable.
Usually, rare earth minerals occur together in the same ore, and they are chemically closely related. In nature they never exist as elemental metals; instead they form a variety of minerals such as silicates, phosphates, fluorides, and carbonates.
Uses of rare earth metals
Rare earth metals have several unique magnetic, chemical and luminescent properties. They play a strategic role in many industrial and consumer sectors, often in combination with other metals. The main applications are:
- Rare earth permanent magnets (electric vehicles, clean energy production, healthcare, consumer electronics).
- Electron guns (scientific instruments such as scanning electron microscopes)
- Magnetostriction (sensors)
- Catalysts (petroleum refining)
- Organic complexes (production of solar cells)
However, by far the most important of these metals commercially, are rare earth magnets. You can find more information on these by clicking here.
Some of the most important metals and their uses are summarised in this table:
| Rare earth metal | Chemical symbol | Atomic number | Typical uses |
| Scandium | Sc | 21 | Aerospace components, mercury vapour and metal halide lamps |
| Yttrium | Y | 39 | Lasers, superconductors, microwave filters, energy efficient lighting |
| Lanthanum | La | 57 | Catalysts in oil refineries, high refractive index glass, and lenses, battery electrodes, hydrogen storage |
| Cerium | Ce | 58 | Catalysts, ceramic and glass colourings, flints |
| Praseodymium | Pr | 59 | Rare earth magnets, lasers, ceramic and glass colourings, flints |
| Neodymium | Nd | 60 | Rare earth magnets, lasers, ceramic and glass colourings, ceramic capacitors, electric vehicle motors |
| Promethium | Pm | 61 | Luminous paints, nuclear batteries |
| Samarium | Sm | 62 | Rare earth magnets, lasers, control rods in nuclear reactors |
| Europium | Eu | 63 | Lasers, phosphors, mercury vapour and fluorescent lamps |
| Gadolinium | Gd | 64 | Lasers, x-ray tubes, computer memories, neutron capture, magnetostrictive alloys. |
| Terbium | Tb | 65 | Rare earth magnets, lasers, phosphors, magnetostrictive alloys, sonar systems, fuel cells |
| Dysprosium | Dy | 66 | Rare earth magnets, lasers, phosphors, magnetostrictive alloys |
| Holmium | Ho | 67 | Rare earth magnets, lasers, spectrometers |
| Erbium | Er | 68 | Lasers, fibre optics |
| Thulium | Tm | 69 | Lasers, x-ray machines, metal halide lamps |
| Ytterbium | Yb | 70 | Lasers, seismology, chemical processes, nuclear medicine |
| Lutetium | Lu | 71 | PET scan detectors, high refractive index glasses, oil refinery catalysts, LED light bulbs. |
Investing in rare earth metals
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