Rare earth elements, a group of 17 metallic elements, possess unique magnetic, luminescent, and electrical properties that make them valuable for various industrial uses. Despite the presence of these elements in mineral ores worldwide, their production is predominantly based in China due to the complex extraction processes. The rare earths’ electron structure makes it difficult to separate them from one another, a challenge heightened by their similar atomic properties.
Among these elements, certain rare earths such as neodymium, dysprosium, and samarium are noted for their magnetic characteristics. These elements have numerous unpaired electrons that allow them to store substantial magnetic energy, making them ideal for powerful magnets. Neodymium magnets, for example, are capable of storing 18 times the energy of an iron magnet of the same size, making them essential in electric motors, wind turbines, aircraft guidance systems, and electronics. However, pure rare earth elements lose their magnetism at higher temperatures, so they are alloyed with metals like iron and cobalt to form stronger and more temperature-stable magnets. These metal alloys, though effective, add costs due to additional processing, especially for recycling purposes.
Other rare earths, including europium, yttrium, erbium, and neodymium, possess luminescent properties, emitting light when exposed to electromagnetic radiation. These properties make them valuable for energy-efficient lighting, such as LEDs and compact fluorescent bulbs, as well as in fibre-optic signal amplification. Europium’s red light, for instance, was critical in early colour televisions, while erbium amplifies signals in high-capacity fibre-optic cables, supporting global internet and communication networks. Additionally, lasers, particularly those using yttrium-aluminium-garnet (YAG) doped with erbium or neodymium, benefit from these luminescent elements, with applications in medicine, manufacturing, and military range-finding technologies.
The electrical properties of rare earths like cerium, lanthanum, neodymium, and praseodymium make them essential for nickel-metal hydride (NiMH) batteries. These batteries are used in hybrid vehicles and portable power tools due to their high energy density and durability. Mischmetal, a mixture of these elements, is cheaper to produce because they do not need to be fully separated, reducing production costs.
Cerium and lanthanum, in particular, play a catalytic role in various industries. Cerium is used in catalytic converters, converting toxic carbon monoxide into carbon dioxide, while lanthanum aids in refining crude oil into usable products like gasoline. Both elements are more abundant and thus more economically viable for these applications.
Geologically, rare earth elements are found at low concentrations in rocks worldwide, but economically viable deposits are limited. Historically, rare earth production has relied on three primary minerals: monazite, bastnaesite, and ion-adsorption clays, each with varying concentrations of light and heavy rare earths. The distribution of light and heavy elements influences the economic value of deposits, as heavier rare earths are rarer and more expensive.
Monazite was mined extensively until the 1950s but contains high levels of radioactive thorium, leading to environmental concerns. This, along with thorium’s radioactivity, shifted focus to bastnaesite, which became the main rare earth source in the 1960s. While bastnaesite is less radioactive, it contains carbonate fluoride, which can present health hazards if not carefully managed. In the 1970s, China discovered ion-adsorption clays with high heavy rare earth content. These clays, concentrated mainly in Southern China, now account for a significant share of heavy rare earth production worldwide.
The industrial value of rare earth elements lies in their distinctive properties, from magnetism to luminescence, which are harnessed across a range of advanced applications. Yet, their economic production remains concentrated in a few regions due to both geological and environmental factors, underscoring the specialised processes involved in their extraction and use.
Pensana plc (LON:PRE) explores and mines neodymium, praseodymium, and rare earth minerals. The Company’s flagship assets are the Saltend rare earth refinery project in the United Kingdom and Longonjo neodymium and praseodymium (NdPr) Project in Angola.
