Rare earth elements (REE) or Rare earth metals (REM) are a special group of heavy metals. There are 17 chemical elements including scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymiun (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu ).

The elements scandium (Sc), yttrium (Y) and lanthanum (La) belong to the III group of the table, and the remaining 14 elements correspond to the lanthanide series. With the exception of scandium and yttrium whose atomic numbers are 21 and 39, respectively, the atomic number of the remaining rare earth elements ranges from 57 to 71, and they are classified as light rare earth elements and heavy rare earth elements. The atomic number of the light rare earth elements varies between 57 (lanthanum) and 63(europium); and the atomic number of the heavy rare earth elements ranges between 64 (gadolinium) and 71(lutetium).

Sometimes, they are called lanthanides like the first one of the REE list. Like ordinary metals, REM can form different compounds ( RE oxides and RE salts) which are applied in all life spheres.

Why RARE metals?

It is a question of history. When scientists started to investigate these elements, they supposed that the average crustal abundance was rare. It is not true: investigations showed us that REE surpass lead by 10 times, molybdenum by 50 times, gold by 200 times. These elements are definitely difficult to mine, however there is a wide list of metals more rarely found. It is convenient to comment that the most abundant element of the rare earth elements in the earth’s crust is cerium and the less abundant is thulium.

Rare earth mineral deposits

The main mineral deposits from which the largest proportion of REE   is mined are bastnasite (fluoro-carbonate mineral), monazite (phosphate mineral), loparite (complex mineral that may contain titanium, niobium and tantalum, sodium, calcium, strontium and iron) and laterite clays (composed of ferric oxide, alumina and silica). Other minor sources of REE are allanite (mineral formed by combinations of calcium, iron, aluminum and silicon), apatite (phosphate carbonate and fluor), euxenite (niobium, tantalum, and titanium), fluorite (calcium and fluor), gadolinite (iron, beryllium, and silicon), perovskite (calcium, titanium), sphene (calcium, titanium, silicon, and fluor), zircon (silicon and zirconium) and xenotime (mineral phosphates), among others.

The processing of rare earth elements is costly and complex because the mineral deposits where they are found can contain numerous substances that must be identified and isolated using several separation processes. In addition, many rare earth deposits contain thorium which is a radioactive element that complicates the extraction of rare earths due to the problems associated with the safe separation of this element.

1. Mining: Rare earth elements are usually found in mineral deposits, often in combination with other elements. The first step in processing is to mine the ore containing the rare earth elements.

2. Crushing and Grinding: The mined ore is crushed and ground into smaller particles to increase the surface area for further processing.

3. Beneficiation: The crushed and ground ore undergoes beneficiation, which involves separating the rare earth minerals from the other minerals present in the ore. This can be done through processes such as gravity separation, magnetic separation, or flotation.

4. Leaching: In some cases, the rare earth minerals are leached from the ore using chemicals or acids. This helps to separate the rare earth elements from the rest of the minerals.

5. Solvent Extraction: Solvent extraction is a common method used to separate and purify the rare earth elements. It involves using organic solvents to selectively extract the desired elements from a solution.

6. Precipitation and Crystallization: Once the rare earth elements are extracted, they may undergo precipitation or crystallization processes to further purify them and remove impurities.

7. Refining: The purified rare earth elements are further refined through processes such as distillation, electrolysis, or ion exchange to obtain high-purity individual elements.

8. Forming: The final step in processing rare earth elements involves shaping them into usable forms such as powders, alloys, or compounds, depending on their intended applications.

Rare earth metals applications



This rare earth element forms scandium-aluminum alloys used in sports equipment and aerospace industry. For example these alloys have been utilized to manufacture   golf shafts, baseball bats, bicycle frames, and Russian MIG fighter planes.  The isotope scandium-46 is used as a tracer to observe oil factions in oil refining processes or to discover escapes in underground pipelines. There is an opinion that scandium is used in production of 5G chips and other types of semiconductors.


Yttrium improves the strength of magnesium and aluminum alloys. It is employed in microwave filters for radar and is used in white LED lights. It has been utilized in lasers designed for metal cutting and as a catalyst in polymerization processes.  Also, this rare earth is a component of many automobile electrical sensors. In addition, yttrium oxide is used to prepare superconductors and helps improve the shock and heat resistance of camera lenses.   The radioactive isotope yttrium-90 is used in the treatment of cancer.


Lanthanum is used in nickel metal hydride batteries that are employed in hybrid cars. Also, a lanthanum-nickel alloy is used for the storage of hydrogen   in hydrogen-powered vehicles. In addition, lanthanum is utilized in carbon lighting applications and for making optical glasses and night vision goggles. Likewise, it is used as a catalyst in oil refining processes.  Radioactive lanthanum isotopes have been used in the treatment of cancer.


This element is employed in energy saving light bulbs and flat screen television.  It is a constituent of mischmetal alloy used in “flint” for torches and cigarrete lighters. Also, it is utilized in vehicle catalytic converters and as red-color pigment.   Cerium oxide is a polishing agent for automotive glass and mirrors.


Praseodymium is a component of several alloys. It forms with magnesium a high strength alloy used in aircraft engines.  Other alloys are employed in permanent magnets. Also, the mischmetal alloy contains praseodymium. Praseodymium oxide is a constituent of goggles used during glass blowing and welding. Besides, it is utilized in carbon arc electrodes for illumination.


Neodymium forms alloys with boron and iron that are used to construct strong permanent magnets employed in microphones, amplifiers, mobile phones, electronic musical instruments, speakers, wind turbines and in many electrical motors used in cars. Neodymium is employed to make lasers utilized in cosmetic and eye surgery, in the treatment of skin cancers, and as laser pointers and laser range-finders. Likewise, neodymium is used in the goggles employed by glassmakers and welders, and in the glass of tanning booths because it transmits UV rays but does not allow infrared rays that produce heat to pass through the glass. Also, this rare earth element is employed to color crystals with pleasant shades of gray, violet and wine red. In addition, neodymium oxide can be utilized as a catalyst in some polymerization reactions.


Promethium is used in nuclear batteries of guided missiles, and as a source of x-rays in measuring devices, its isotope is used in self-luminous paint and signs, X-ray Fluorescence (XRF) Analyzers to ensure accurate and precise measurements in XRF analysis. Manufacturers apply Promethium-147 in thickness gauges for measuring the thickness of materials, particularly in industries like metalworking and construction.


Samarium cobalt magnets, also known as SmCo magnets, are one of the most powerful and permanent magnets available. They are used in various applications such as electric motors, headphones, sensors, and aerospace equipment. Samarium is also used in catalysts, as a neutron absorber in nuclear reactors, in targeted radiation therapy for the treatment of bone cancer and other bone-related conditions.


This rare earth is used to absorb neutrons in the control systems of nuclear reactors. Europium is also employed in the manufacture of superconducting alloys and fluorescent lamps.  Low energy bulbs contain europium to give a more natural light, by balancing blue light with red light. In addition, this element is used in the printing of bills to detect if they are true or false as it lights up in red under UV light. Therefore the fakes can be detected by the lack of this red glow


Gadolinium is used to absorb neutrons in nuclear reactors. Also, this rare earth is used to prepare suitable alloys in the manufacture of magnets, data storage disks and electronic components. Likewise, gadolinium alloys with iron and chromium are resistant to high temperatures and oxidation. Additionally it is used in the diagnosis of cancerous tumors.


Terbium is used in low power bulbs and mercury lamps. It has been utilized to improve the safety of physicians and patients who use x-rays by allowing the same quality image to be produced with a much shorter exposure time. Also, terbium salts are used in laser devices.


Dysprosium is used in the manufacture of magnets employed in motors or generators of electric vehicles and wind turbines. It is also utilized in the manufacture of lamps that provide intense white light. In addition is used  in the control rods of nuclear reactors.


This rare earth is used to make magnets and to absorb neutrons in nuclear reactors. The main application of holmium is magnetostrictive materials used in sensors, actuators, and acoustic devices. Holmium oxide is used as a colorant in glass and ceramics. Holmium isotopes, such as holmium-165, are important for Nuclear Magnetic Resonance (NMR).


Erbium is utilized to amplify broadband signals transported by fiberglass cables. In addition, it is used to absorb infrared radiation in the safety glasses of metalworkers and welders. Also, erbium is used to color the glasses.


This rare earth is used to make light and portable x-ray machines for medical use. Additionally, thulium is utilized in surgery lasers and in development of high-temperature superconducting materials. Thulium-170 is used as a radiation source in nuclear energy applications, such as radiography and well logging. 


Ytterbium is used as an ecological catalyst to replace toxic catalysts and pollutants. Ytterbium is a compound in atomic clocks, which are highly accurate timekeeping devices. Also ytterbium-doped fiber lasers are widely used in industrial applications such as cutting, welding, and marking. Ytterbium-doped fibers can generate high-power laser beams with excellent beam quality and efficiency.


This rare earth element is used as a catalyst in the cracking of hydrocarbons, in targeted radionuclide therapy for the treatment of certain types of cancer, such as neuroendocrine tumors and prostate cancer. Lutetium-based scintillators are applied in medical imaging devices, such as positron emission tomography (PET) scanners.