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Encyclopedia of Physical Science and Technology EN014A-653 July 28, 2001 20:55

Rare Earth Elements and Materials 3

TABLE I Discovery of the Elements
Name Discoverer (nationality) (year) Origin
Lanthanum C. G. Mosander (Swedish) (1839) (Greek), lanthanein “to lie hidden”
Cerium M. H. Kalproth (German) Ceres, an asteroid discovered only 2 years prior
J. J. Berzelius (Swedish)
W. Hinsinger (Swedish) (1803)
Praesodymium and C. A. von Welsbach (Austrian) Separated from a mixture originally called didymia. (Greek)
neodymium (1885) Prasios (green), neo (new), didymos (twin)
Promethium J. A. Marinsky (Greek mythology) Prometheus, stole fire from the gods. All
L. E. Glendenin and C. D. Coryell isotopes of prometheum are radioactive
(American) (1945)
Samarium P. Lecoq de Boisboudran (French) Samarskite, a mineral. The mineral was named for a Russian
(1879) mining official Col. Samarski
Europium E. A. Demarcay (French) (1901) Europe
Gadolinium J. C. G. Marignac (Swiss) (1886) Gadolinite, a mineral. The mineral was named for J. Gadolin,
a Finnish chemist
Terbium C. G. Mosander (Swedish) (1843) Ytterby, a Swedish village. Site of a quarry where many rare
minerals containing “rare earths” were first discovered
Dysprosium P. Lecoq de Boisbaudran (French) (Greek) disprositos, “hard to get at” from the difficulty in
(1886) isolating this element
Holmium J. L. Soret (Swiss) (Latin) Holmia, latin for Stockholm, Cleve’s native city
P. T. Cleve (Swedish) (1878)
Erbium C. G. Mosander (Swedish) Ytterby, Swedish village. Mosander discovered erbium but
(1842) Urbain first produced fairly pure material
G. Urbain (French) (1905)
Thulium P. T. Cleve (Swedish) (1879) Thule, ancient name for Scandanavia
Ytterbium J. C. G. Marignac (Swiss) (1878) Ytterby, Swedish village
Lutetium C. A. von Welsbach (Austrian) Lutetia, ancient name for Paris
G. Urbain (French)
C. James (American) (1907)
Yttrium C. G. Mosander (Swedish) (1843) Ytterby, Swedish village. Isolated by Mosander from mixture
discovered by Gadolin (1794)

The reason for this surprising lag between initial discov- tance as a geological tool to determine the evolutionary
ery and the beginnings of a serious study and exploitation history of a given sample. This will be discussed briefly
of the rare earths lies in the facts of their mineralogical ori- later on.
ginandtheirgreatchemicalsimilarityleadingtoenormous In spite of this great mineralogical diversity only a
difficultiesinseparationandisolationoftheindividualele- very few rare earth-bearing minerals occur in sufficient
ments. These issues are discussed in the following section. concentration to justify commercial exploitation as an
ore. These are, roughly in order of current commercial
importance, bastnasite (bastnaesite is another spelling),
B. Natural Occurrence and Abundance
REFCO 3 ; monazite, REPO 4 ; and xenotime, YPO 4 (the
of the Rare Earths
same chemical formula as monazite but contains mostly
yttrium). Here the symbol RE refers to a mixture of
1. Geological Distribution
rare earths. In addition, apatites (Ca, RE) 5 (PO 4 ) 3 F and
The rare earths are very widely distributed in the earth’s uranium-bearing minerals such as uraninite and uranoth-
crust and exhibit a great diversity in the geological type orite contain commercial quantities.
of the deposits. They are found in all possible geolog- Exploitable deposits of the above minerals are found on
ical domains: igneous-hydrothermal, metamorphic, and all six continents as shown in Table II, which lists world
sedimentary. They occur as an important constituent in reserves in units of tons of Reoxide.
more than 100 different minerals and in trace quantities in Note the striking fact that 80% of the world reserves
many others. In fact, the study of the distribution of rare of rare earths are located in China with 11% in North
earths at trace levels in minerals is of considerable impor- America and 5% in India. Both the Chinese (at Bayan Obo,