Rare Earth Elements

Rare Earth Elements

Cerium, Dysprosium, Erbium, Europium, Gadolinium, Holmium, Lanthanum, Lutetium, Neodymium, Praseodymium, Samarium, Terbium, Thulium, Ytterbium, Yttrium, Ferrocerium, Monazite, Bastnasite, Mischmetal

The principal economic sources of rare earths are the minerals Bastnasite, Monazite, and Loparite and the lateritic ion-adsorption clays. The rare earths are a relatively abundant group of 17 elements composed of Scandium, Yttrium, and the Lanthanides. The elements range in crustal abundance from Cerium, the 25th most abundant element of the 78 common elements in the Earth's crust at 60 parts per million, to Thulium and Lutetium, the least abundant rare-earth elements at about 0.5 part per million. The elemental forms of rare earths are iron gray to silvery lustrous metals that are typically soft, malleable, and ductile and usually reactive, especially at elevated temperatures or when finely divided. The rare earths' unique properties are used in a wide variety of applications.

The rare earth elements (REE) form the largest chemically coherent group in the periodic table. Though generally unfamiliar, the REE are essential for many hundreds of applications. The versatility and specificity of the REE has given them a level of technological, environmental, and economic importance considerably greater than might be expected from their relative obscurity. The United States once was largely self-sufficient in these critical materials, but over the past decade has become dependent upon imports. In 1999 and 2000, more than 90% of REE required by U.S. industry came from deposits in China.

Although the 15 naturally occurring REE are generally similar in their geochemical properties, their individual abundances in the Earth are by no means equal. In the continental crust and its REE ore deposits, concentrations of the most and least abundant REE typically differ by two to five orders of magnitude. As technological applications of REE have multiplied over the past several decades, demand for several of the less abundant (and formerly quite obscure) REE has increased dramatically.

The diverse nuclear, metallurgical, chemical, catalytic, electrical, magnetic, and optical properties of the REE have led to an ever increasing variety of applications. These uses range from mundane (lighter flints, glass polishing) to high-tech (phosphors, lasers, magnets, batteries, magnetic refrigeration) to futuristic (high-temperature superconductivity, safe storage and transport of hydrogen for a post-hydrocarbon economy).

**Image and Source of Information: USGS

***For a more detailed and interactive version of the entire Periodic Table of Elements, please click here: PTE

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