Editing Rare-earth element (section)

==Sources and purification==
In the 1940s, [[Frank Spedding]] and others in the United States, during the [[Manhattan Project]], developed chemical [[ion-exchange]] procedures for separating and purifying rare-earth elements. This method was first applied to the [[actinide]]s for separating [[plutonium-239]] and [[neptunium]] from [[uranium]], [[thorium]], [[actinium]], and the other actinides in the materials produced in [[nuclear reactor]]s. Plutonium-239 was very desirable because it is a [[fissile material]].

The principal sources of rare-earth elements are the minerals [[bastnäsite]] ({{chem2|RCO3F}}, where R is a mixture of rare-earth elements), [[monazite]] ({{chem2|XPO4}}, where X is a mixture of rare-earth elements and sometimes thorium), and [[loparite]] ({{chem2|(Ce,Na,Ca)(Ti,Nb)O3}}), and the [[laterite|lateritic]] ion-adsorption [[clay]]s. Despite their high relative abundance, [[rare-earth mineral]]s are more difficult to mine and extract than equivalent sources of [[transition metal]]s, due in part to their similar chemical properties, making the rare-earth elements relatively expensive. Their industrial use was very limited until efficient separation techniques were developed, such as [[ion exchange]], fractional crystallization, and [[liquid–liquid extraction]] in the late 1950s and early 1960s.<ref>Spedding F., Daane A. H.: "The Rare Earths", John Wiley & Sons, Inc., 1961.</ref>

Some [[ilmenite]] concentrates contain small amounts of scandium and other rare-earth elements, which could be analysed by [[X-ray fluorescence]] (XRF).<ref>{{cite book |title=Hydrometallurgy of Rare Earths |last=Qi |first=Dezhi |publisher=Elsevier |year=2018 |isbn=978-0-12-813920-2 |pages=162–165}}</ref>