The rare earths are not particulary rare, being a family of metals with atomic numbers 58 to 71. More than 100 minerals are known to contain one or more of the rare lanthanides. Only two of these minerals, monazite* and bastnasite**, are commercially important. The challenge with rare earths is their natural concentration to form a deposit and then the separation of rare earth elements. A mineral like monazite may contain half a dozen or more different rare earth elements. Today, a standard procedure is available for separating the rare earth elements from each other. In many lanthanides, pure metal is made by treating its fluorine compound with calcium.
RE = Rare Earth
REM = Rare Earth Metals
REE = Rare Earth Elements
REO = Rare Earth Oxides
TREO = Total Rare Earth Oxides
LREE = Light Rare Earth Elements (La-Sm)
HREE = Heavy Rare Earth Elements (Eu-Lu)
The rare-earth metals or lanthanides were divided into three categories by Jöns Jakob Berzelius (1779–1848) :
- The cerium subgroup,which comprised of 57-lanthanum, 58-cerium, 59-praseodymium, 60-neodymium, and 62-samarium (61-Promethium does not occur naturally).
- The terbium subgroup includes 63-europium, 64-gadolinium, and 65-terbium.
The remaining lanthanides are placed in the yttrium subgroup. Strictly speaking, yttrium is not a rare earth. Because the properties of yttrium resemble those of heavy rare earths, its name has been used as a designating adjective.
- The yttrium subgroup includes 66-dysprosium, 67-holmium, 68-erbium, 69-thulium, 70-ytterbium, and 71-lutetium.
The most common lanthanoids in these minerals are, in order, cerium, lanthanum, neodymium, and praseodymium. Monazite mineral also contains thorium and ytrrium.
*Monazite: reddish-brown phosphate mineral containing rare earth (Ce, La, Th, Nd, Y)PO4
**Bastnasite : carbonate fluoride minerals with chemical formula (Ce, La, Y)CO3F
Compiled by LKConsult - January 2009
|Lanthanum||La||57||LREE (Light Rare Earth Elements)||cerium subgroup|
|Europium||Eu||63||HREE (Heavy Rare Earth Elements)||terbium subgroup|
Source: tables numériques et formulaires A.Olza, F.Taillard ; ed SPES 1978 / manual of mineralogy ; James D. Dana ed. John Wiley & sons; Wikipedia / http://www.periodni.com/; http://www.chemistryexplained.com/elements/index.html;http://www.lenntech.com/periodic-chart.htm; HEFA Rare Earth Canada.