Rare earths are not rare, just maddeningly hard to separate
Cerium, one of the 17 rare-earth elements, is more common in Earth's crust than copper. The name misleads: these metals are plentiful but spread thinly, locked in compounds and chemically so alike that chemists spent over a century untangling them, announcing dozens of false new elements along the way.
The story begins in 1787 at a quarry in Ytterby, a Swedish village. A black mineral found there reached Johan Gadolin in Turku, who extracted an unknown oxide he named yttria. In 1803 Jöns Jacob Berzelius and Wilhelm Hisinger found another, ceria, in a Swedish mineral. Both turned out to be mixtures. Carl Gustav Mosander split ceria in 1839 and yttria in 1842, producing names such as lanthana, terbia and erbia. Ytterby alone lends its name to four elements.
Separating these near-twins was so hard that confusion reigned. Later chemists even swapped the names erbium and terbium, and false discoveries like mosandrium and philippium piled up, with some counts exceeding a hundred. Spectroscopy helped from 1879, revealing samarium, then gadolinium in 1886 and europium in 1901. Henry Moseley's X-ray work then showed there must be exactly 15 lanthanides, exposing a gap at element 61. Moseley was killed in the First World War in 1915, and that missing element, promethium, was only made artificially in 1945, the last rare earth found.
Purifying them properly came with the Manhattan Project, when Frank Spedding and colleagues developed ion-exchange methods in the 1940s. Before that, chemists relied on repeated precipitation and crystallisation.
Today these metals end up in magnets, catalysts, lasers, glass, electric vehicles, wind turbines and smartphones. Getting usable amounts means processing huge volumes of ore, which is costly and energy hungry, and deposits often contain thorium or uranium. China raised its share of production from 21% to 60% between 1985 and 1995, and by 2019 met around 90% of world demand.
Source: Rare-earth element
