Geologist Ricardo Alonso reconstructs in this article the etymological and scientific origin of the lanthanides, from their discoveries in 19th-century Europe to their current strategic role as pillars of advanced technology and the energy transition. Mythologies, European cities, and pioneering scientists to nuclear laboratories—the names of the lanthanides reflect a fascinating scientific journey that anticipated their current role as critical inputs.
By Panorama Minero
As we have pointed out on other occasions: “Rare Earths are not rare; what is rare are Rare Earth deposits.” That said, it only remains to recall that they are a group of 15 elements of the Lanthanide Group of the Periodic Table of Chemical Elements (Mendeleev, 1869), ranging from number 57 (lanthanum) to 71 (lutetium).
The history of their discovery and the names of their discoverers is one of the fascinating chapters of modern chemistry. It all begins when minerals containing metallic oxides that were not the common oxides such as those of silicon, iron, calcium, or magnesium were discovered in a Swedish mine. They were new and rare, and since at that time the term “earth” was applied to any oxide insoluble in water and resistant to heat, they came to be known as “rare earths.”
Cerium (Ce), element number 58, received its name from the asteroid Ceres and was originally discovered independently by the renowned chemists Wilhelm Hisinger (1766–1852) and Jacob Berzelius (1779–1848) in Sweden, and by Martin H. Klaproth (1743–1817) in Germany. It was the first lanthanide to be discovered in 1803, two years after the asteroid or dwarf planet Ceres. Ceres took its name from the Roman goddess of agriculture, from which the word “cereal” derives. It was formerly used in lighter flints, medicine, and artillery tracer bullets. The Swedish chemist J. Berzelius, one of the fathers of modern chemistry, is also credited with proposing the current chemical symbols. M. H. Klaproth, for his part, is considered the father of Analytical Chemistry.
Dysprosium (Dy), element number 66, received its name from the Greek word meaning “inaccessible” and was discovered in 1886 by the French chemist Paul-Émile Lecoq de Boisbaudran (1838–1912). He is also credited with the discovery of gallium, samarium, gadolinium, and europium.
Erbium (Er), element number 68, was discovered in 1843 by the Swedish chemist Carl Gustaf Mosander (1797–1858), who named it after the locality of Ytterby in Sweden. Mosander studied the mineral gadolinite from the Ytterby mine and separated three oxides from “yttria,” which were yttria, erbia, and terbia, all referring to that locality and later renamed yttrium, erbium, and ytterbium. Yttrium (Y), element number 39, is considered indirectly among the rare earths, but it is not part of the select group of lanthanides. The same applies to scandium (number 21).
Europium (Eu), element number 63, was discovered in 1901 by the French chemist Eugène-Anatole Demarçay (1852–1904), who named it after Europe. Today it provides the red color in screens of mobile phones, computers, and televisions.
Gadolinium (Gd), element number 64, was discovered in 1880 by the Swiss chemist Jean Charles Galissard de Marignac (1817–1894), but was later isolated in 1886 by the French chemist Paul-Émile Lecoq de Boisbaudran. Both the mineral gadolinite and the element gadolinium refer to and honor the Finnish chemist and mineralogist Johan Gadolin (1760–1852), considered the father of Finnish chemistry.
Holmium (Ho), element number 67, was discovered in 1879 by the Swedish chemist and geologist Per Teodor Cleve (1840–1905), who named it after Stockholm, his native city, whose Latin name is Holmia. Cleve also discovered thulium and scandium. The strong magnetism of holmium makes it essential in modern applications.
Ytterbium (Yb), element number 70, was discovered in 1878 by Galissard de Marignac. Its name also comes from the Ytterby mine in Sweden.
Lanthanum (La), element number 57, was discovered in 1839 by Mosander. The name comes from the Greek meaning “hidden.” It is a soft metal that can be cut with a knife. Its former use was in lighter flints. Today it has technological applications that make it critical as a catalyst in petroleum refining, in nickel-metal hydride batteries for hybrid vehicles, in the treatment of kidney failure, and in high-quality optical lenses for cameras, telescopes, and infrared-absorbing glass.
Lutetium (Lu), element number 71, was discovered in 1907 by the French chemist Georges Urbain (1872–1938), who named it after Lutetia, the ancient name of Paris. It is the heaviest and hardest of the rare earth elements.
Neodymium (Nd), element number 60, was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach (1858–1929). Forty years earlier, Mosander had named what he thought was a new element “didymium,” considering it a twin of lanthanum (from the Greek “didymos,” meaning twin). Auer von Welsbach separated it into two distinct elements: neodymium (“new twin”), which produced pinkish-red salts, and praseodymium (“green twin”), due to the green color of its salts (prasios in Greek). Neodymium combined with boron forms alloys used to make the most powerful permanent magnets in modern technologies, used in everything from hard drives to wind turbines, electric motors, high-power lasers, and magnetic levitation trains.
Praseodymium (Pr), element number 59, was explained together with neodymium, sharing the same discoverer and similar uses, especially in the energy transition.
Promethium (Pm), element number 61, was discovered in 1945 from uranium fission products by American scientists Jacob A. Marinsky, Lawrence E. Glendenin, and Charles D. Coryell at Oak Ridge National Laboratory (Tennessee). It is a radioactive element used in atomic batteries that power space probes and satellites. It was named after the mythological Titan Prometheus, who stole fire from the gods to give it to humans, symbolizing energy and radioactivity obtained through technology.
Samarium (Sm), element number 62, was discovered in 1879 by the Frenchman Paul-Émile Lecoq de Boisbaudran, also the discoverer of gallium, gadolinium, and europium. The discovery was made while studying samples of the mineral samarskite, a complex oxide from the Ural Mountains in Russi. The mineral was named in honor of the Russian military engineer and geologist Vasili Samarsky (1803–1870), who provided the samples. The element samarium was named after the mineral and indirectly after the geologist. It was the first chemical element named after a person.
A decade later, the same occurred with gadolinium. In the 20th century, other elements were also named after scientists, such as curium (after Marie and Pierre Curie), einsteinium (after Albert Einstein), fermium (after Enrico Fermi), mendelevium (after Dmitri Mendeleev), nobelium (after Alfred Nobel), and lawrencium (after Ernest Lawrence), as well as transactinides like rutherfordium, bohrium, copernicium, and others.
Terbium (Tb), element number 65, was discovered in 1843 by Carl Mosander and named after Ytterby. Today it is used especially for the bright green color in electronic screens and in high-performance magnets.
Thulium (Tm), element number 69, was discovered in 1880 by Per Teodor Cleve, who named it after Thule, a mythical northern land representing the edge of the known world.
Yttrium and scandium are broadly included among rare earths, although they are not part of the 15 lanthanides.
The first six lanthanides—lanthanum, cerium, promethium, praseodymium, neodymium, and samarium—are known as “Light Rare Earths,” while the rest—europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium—are known as “Heavy Rare Earths.” Except for promethium, which was discovered in artificial radioactive residues, the rest are found as metallic oxides in around 300 minerals, though only a few are economically significant, such as bastnäsite, monazite, xenotime, gadolinite, loparite, and huanghoite.
Most rare earth elements were discovered in the 19th century, mainly by European chemists—especially Swedish, German, Austrian, and French.
Most of their names come from localities or old Latin toponyms (holmium, lutetium, thulium), except for two that refer to people (samarium and gadolinium). Others derive from Greek (dysprosium, lanthanum) and even mythology (cerium, promethium). From an anecdotal origin and almost useless in their beginnings, today rare earths drive the fine technology of the planet.
