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Rare Earth Elements

Seventeen metallic elements that only exist in other minerals.

What are Rare Earth Elements?

The rare earth elements (REEs) are a set of 17 metallic elements. They include the 15 lanthanides grouped together on the periodic table of the elements, plus scandium and yttrium. In nature, REEs do not exist individually, like gold or copper metals often do, but instead occur in minerals as either minor or major constituents, primarily in bastnaesite, monazite, loparite, and lateritic ion-absorption clays. REEs are categorized as either light—those with the lowest atomic numbers—or heavy, which have higher atomic numbers and are less common and more expensive.

REEs are not as rare as their name implies. They were deemed rare during the 18th and 19th centuries because they were relatively rare compared to other “earths” (materials that could not be changed further by heat), such as lime and magnesia. Thulium and lutetium are the two least abundant REEs, yet they are still 200 times more abundant in the Earth’s crust than gold. The most abundant REEs are cerium—which is as abundant as copper—and yttrium, lanthanum, and neodymium, which are similar in abundance to commonly used metals such as chromium, nickel, zinc, molybdenum, tin, tungsten, and lead. However, it is highly unusual to find REEs in concentrations high enough for economical extraction, which makes them rare in terms of their availability.

Refining involves physical separation of an REE from its host ore by various chemical techniques, sometimes involving thousands of steps. Each REE and its respective ore is different and requires different chemical techniques for refining (depending on melting point and vapor pressure, and other physical properties of the element). This intensive processing comes at a huge cost, raising the price of the element substantially.

The demand for rare earth elements saw its first explosion in the mid-1960s, as the first color television sets used europium to produce color images. Demand for REEs then rose steadily with technological advancements in defense, aviation, industrial, and consumer electronics products. Today, and for the foreseeable future, clean energy, advanced medical technologies, and defense applications promise to accelerate demand markedly.

Promising new research holds the potential to extract REEs and critical minerals from waste materials such as acid mine drainage, waste coal, heavy mineral sands tailings, fly ash from power plants, e-waste, and slag from steelmaking – while simultaneously cleaning up the environment.

Light Rare Earth Elements & Their Uses

Cerium Automobile catalytic converters, glass polishing and coloring, metal alloys, water purification, and flints.
Europium Fluorescent lighting, phosphors, lasers, and as a relaxant in nuclear magnetic resonance spectroscopy.
Gadolinium Magnetic resonance imaging (MRI) contrast agent, nuclear reactor rods, lasers, x-ray tubes, computer memory, high refractive index glass, neutron capture, steelmaking, and as a relaxant in nuclear magnetic resonance spectroscopy.
Lanthanum Night-vision optics, as a hydrogen absorber in rechargeable batteries, high refractive index glass, camera lenses, and catalysts for petroleum refining.
Neodymium The strongest magnets known (neodymium-iron-boron magnets), smartphones, electric vehicles, permanent magnets for wind turbines and data storage systems, medical and industrial lasers, laser range-finders, capacitors, missile guidance systems, electric motors, communications, and glass and ceramics colorant.
Praseodymium Permanent magnets for wind turbines and data storage systems, in alloys with magnesium to form aircraft engines, lasers, film studio lighting, yellow ceramic pigment, and flint steel.
Promethium Luminous paint, nuclear batteries, and as a beta radiation source.
Samarium Permanent magnets that are corrosion-resistant and stable at high temperatures, lasers, precision-guided weapons, white-noise generation in military stealth technology, lasers, masers, and nuclear reactor control rods.
Scandium Light alloys for the aerospace industry, radioactive tracers, and lamps. (Though not technically classified as a light rare earth metal, scandium is found in most REE deposits, and with atomic number 21 is the lightest REE.)

Heavy Rare Earth Elements & Their Uses

Dysprosium Permanent magnets for wind turbines, data storage systems and surgical robots, lasers, magnetostrictive alloys, and cooling of nuclear reactor fuel rods.
Erbium Laser repeaters, amplifiers in fiber-optic data transmission, glass colorant, and vanadium steel.
Holmium Highest-power magnets, lasers, and calibration of spectrophotometers.
Lutetium Positron emission tomography (PET) scanners, high refractive index glass, catalysts, and LEDs.
Terbium TV screens and solid-state hard drives, phosphors for lighting, high-power/high-temperature magnets, lasers, fluorescent lamps, magnetostrictive alloys, and sonar systems.
Thulium Lasers, metal halide lamps, portable x-ray machines, and ceramic magnetic materials.
Ytterbium Fiber optic technology, solar panels, infrared lasers, stainless steel, and nuclear medicine.
Yttrium Yttrium aluminum garnet (YAG) lasers, as a red phosphor, superconductors, fluorescent tubes, LEDs, cancer treatment, alloying agents, ceramics, and in the polymerization of ethylene. (Although light, with atomic number 39, yttrium is included with heavy REEs for its similar chemical and physical properties.)

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