Rare earth element
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- "Rare earth" redirects here, for other uses, see rare earth (disambiguation).
"Rare earth elements" and "rare earth metals" are trivial names sometimes applied to a collection of sixteen chemical elements in the periodic table, namely scandium, yttrium, and fourteen of the fifteen lanthanides (excluding promethium), which naturally occur on the Earth. The former two are included as they tend to occur with the latter in the same ore deposits. Some definitions additionally include the actinides.
"Earth" is an obsolete term for oxide. At the time of their discovery, earths of these elements were believed to be scarce in abundance as minerals. However, the term "rare earth" is now deprecated by IUPAC, as these elements are in fact relatively abundant in the Earth's crust; the most abundant, cerium, at 68 parts per million, is the 25th most abundant element in the crust, more common than lead, while even the least abundant "rare" earth element, lutetium, is 200 times more abundant than gold.
The principal economic sources of rare earth elements are the minerals bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. Despite their relative abundance, however, these are more difficult to mine and extract than the sources of transition metals (due in part to their very similar chemical properties), making them relatively expensive.
The following abbreviations are often used:
- REE = rare earth elements
- LREE = light rare earth elements (La-Sm)
- HREE = heavy rare earth elements (Eu-Lu)
For more details of the properties and uses of these elements, refer to the lanthanides article.de:Metalle der Seltenen Erden el:Σπάνιες γαίες es:Tierras raras eo:Rara tero fr:Terres rares ko:희토류 원소 is:Sjaldgæfur jarðmálmur ja:希土類元素 pt:Terra-rara ru:Редкоземельные элементы sv:Sällsynt jordartsmetall zh:稀土金属
