Today, let’s take a look at interesting facts about Erbium and answer the following questions: “Why Is Erbium Considered A Rare Earth Element?”, and “Why Is Erbium Considered A Critical Raw Material?”

For more information, check out the light rare earth elements (LREEs) as a group, the heavy rare earth elements (HREEs) as a group, and all rare earth elements (REEs). Be sure to check out all other critical raw materials (CRMs), as well.

Why Is Erbium Considered A Rare Earth Element?

Erbium is considered a rare earth element because it is one of the 15 lanthanide elements that form the core of the rare earth element group. With atomic number 68, erbium is positioned between holmium (67) and thulium (69) in the lanthanide series, which extends from lanthanum (atomic number 57) through lutetium (atomic number 71). As a lanthanide, erbium exhibits all the characteristic chemical properties that define this group, including the typical trivalent oxidation state (Er3+) and an ionic radius that follows the systematic “lanthanide contraction” – the progressive decrease in ionic radius from lanthanum to lutetium. This places erbium firmly within the heavy rare earth element subgroup, which comprises “terbium through lutetium (atomic numbers 65 through 71).”

Erbium’s geochemical behavior perfectly aligns with the defining characteristics of rare earth elements. Like all REEs, erbium possesses a high charge (+3) and an ionic radius that prevents its incorporation into common rock-forming minerals during crystallization. This incompatibility causes erbium to remain in residual melts along with other rare earth elements until specialized REE minerals form. With a crustal abundance of 3.5 parts per million, erbium follows the pattern of decreasing abundance among the heavy rare earth elements, being less abundant than dysprosium (5.2 ppm) but more common than thulium (0.52 ppm). Despite being more abundant than silver, gold, or platinum, erbium rarely concentrates into economically viable deposits, following the characteristic behavior of all rare earth elements.

Erbium invariably occurs with other rare earth elements in nature, particularly in minerals that can accommodate heavy rare earth elements. The mineral xenotime ((Y,HREE,Th,U)PO4) specifically includes HREEs in its chemical formula, indicating that erbium and other heavy lanthanides can substitute for yttrium in the crystal structure. Additionally, erbium is found in other REE-bearing minerals including monazite and bastnäsite, though typically in lower concentrations than in HREE-enriched minerals. The principle that “REEs can substitute for one another in crystal structures, and multiple REEs typically occur within a single mineral” applies directly to erbium, which never occurs in isolation but always as part of the rare earth element suite. At Mountain Pass, California, the combined content of all heavy REEs from europium through lutetium plus yttrium totals only 0.4% of the rare earth oxides, illustrating the scarcity of erbium in LREE-dominated deposits.

The combination of erbium’s position in the heavy lanthanide series, its characteristic REE chemistry including the Er3+ oxidation state, its systematic ionic radius, its invariable co-occurrence with other REEs in minerals, and its unique optical properties that enable modern telecommunications unequivocally establishes erbium as a rare earth element.

Why Is Erbium Considered A Critical Raw Material?

Erbium is considered a critical raw material due to its absolutely irreplaceable role in global telecommunications infrastructure, combined with extreme supply concentration and no viable substitutes. The criticality of erbium is starkly demonstrated in fiber-optic technology: “Fiber-optic telecommunication cables can transmit signals over long distances because they incorporate periodically spaced lengths of erbium-doped fiber that function as laser amplifiers. Er is used in these laser repeaters, despite its high cost (~$700/kg), because it alone possesses the required optical properties.” This unique application means that without erbium, the entire global fiber-optic network – which provides “much greater bandwidth than the copper wires and cables they have largely replaced” – cannot function. No other element can replicate erbium’s specific electronic energy levels that enable optical amplification at the 1.55-micrometer wavelength used in telecommunications.

The criticality of erbium is severely amplified by its scarcity and the absolute concentration of heavy rare earth element supply in China. With a crustal abundance of only 3.5 parts per million, erbium is a heavy rare earth element found primarily in China’s ion-adsorption clay deposits, which are “the world’s primary source of the heavy REEs.” Between 2011 and 2017, China produced approximately 84% of the world’s rare earth elements overall, but for heavy REEs like erbium, this concentration approaches 100%. At Mountain Pass, California, the combined content of all heavy REEs from europium through lutetium plus yttrium totals only 0.4% of the rare earth oxides, making Western sources essentially incapable of producing meaningful quantities of erbium. When China announced export restrictions in 2010 through quotas, licenses, and taxes, the high cost of erbium (~$700/kg) reflected both its scarcity and critical importance.

The strategic vulnerability of erbium extends beyond mining to processing and geopolitical risks. The separation of erbium from other rare earth elements requires sophisticated solvent extraction facilities, and “nearly all REE separation and refining” occurs within China. This means that even if rare earth ores containing erbium were mined elsewhere, they would need to be sent to China for processing. The heavy rare earth elements are noted as being “less abundant, and harder to source than the LREEs, and thus command a higher price,” with erbium exemplifying this challenge. The specificity of erbium’s use is emphasized by the statement that it is used “despite its high cost (~$700/kg), because it alone possesses the required optical properties” – indicating that cost is secondary to functionality in critical infrastructure.

The convergence of multiple factors establishes erbium as one of the most critical raw materials for the modern information economy. Expert panels from the National Research Council, U.S. Department of Energy, and European Commission have consistently ranked rare earth elements as having the highest “criticality” factor, with heavy rare earth elements like erbium at the extreme end of supply risk. The complete dependence of global fiber-optic infrastructure on erbium, with no possible substitutes, means that erbium availability directly constrains the expansion and maintenance of internet and telecommunications networks worldwide. Any disruption to Chinese production or exports would immediately impact the ability to manufacture and deploy fiber-optic cables, potentially crippling communications infrastructure development. 

The combination of erbium’s monopolistic role in optical amplification, its occurrence primarily in Chinese ion-adsorption clays, the concentration of all processing capabilities in China, and the absence of any substitute materials establishes erbium as a critical raw material where supply security directly impacts global communications infrastructure and, by extension, the entire digital economy.

Interesting Facts About Erbium

1. Erbium was one of four elements discovered from a single mineral sample (ytterbite) from Ytterby, Sweden in 1843 – the most elements ever isolated from one location.
2. It produces uniquely sharp pink/rose colors in glass and ceramics due to its absorption of green wavelengths, making it valuable for luxury glassware and jewelry.
3. Erbium-doped fiber amplifiers (EDFAs) revolutionized telecommunications by enabling signals to travel thousands of kilometers without electronic regeneration.
4. Its 1.54 μm infrared emission wavelength coincidentally matches the lowest loss window of silica optical fibers, making it ideal for fiber optic communications.
5. Erbium has an unusually high number of unpaired 4f electrons (11), giving it one of the highest magnetic moments among the lanthanides.
6. It exhibits fascinating magnetic phase transitions, transforming from ferromagnetic below 19K to a complex helical antiferromagnetic structure.
7. Er³⁺ ions can upconvert infrared light to visible light through a two-photon absorption process, useful in night vision and biomedical imaging.
8. Natural erbium consists of six stable isotopes, with Er-166 being the most abundant at 33.5% – an unusually even distribution.
9. Erbium oxide has one of the highest melting points among rare earth oxides at 2,344°C, making it valuable for high-temperature applications.
10. It forms pink salts that are among the few naturally colored rare earth compounds visible to the naked eye.
11. Erbium lasers at 2.94 μm are strongly absorbed by water, making them ideal for precise medical procedures with minimal thermal damage.
12. The element shows anomalous thermal expansion behavior at low temperatures due to magnetostrictive effects.
13. Erbium-doped crystals can store optical information through spectral hole burning, a quantum mechanical effect useful for data storage.
14. It has one of the highest thermal neutron absorption cross-sections among stable elements, making it useful in nuclear control rods.
15. Erbium exhibits strong magnetocaloric effects near its magnetic transitions, showing promise for magnetic refrigeration technology.
16. The Er³⁺ ion has over 30,000 distinct electronic energy levels, one of the most complex energy level structures known.
17. Erbium-stabilized zirconia maintains its crystal structure at higher temperatures than other rare earth stabilizers.
18. It shows unusual photoluminescence properties, with some emissions becoming stronger at higher temperatures (anti-thermal quenching).
19. Erbium forms metallic glasses more readily than most other rare earth elements when rapidly cooled from the melt.
20. Its nuclear magnetic resonance properties make Er-167 useful as a shift reagent in NMR spectroscopy, despite being only 23% abundant.

Thanks for reading!