A rare-earth element (REE) or rare-earth metal
(REM), as defined by IUPAC, is one of a set
of seventeen chemical elements in the periodic
table, specifically the fifteen lanthanides,
as well as scandium and yttrium.
Scandium and yttrium are considered rare-earth
elements because they tend to occur in the
same ore deposits as the lanthanides and exhibit
similar chemical properties, but have different
electronic and magnetic properties.
Rarely, a broader definition that includes
actinides may be used, since the actinides
share some mineralogical, chemical, and physical
(especially electron shell configuration)
characteristics.The 17 rare-earth elements
are cerium (Ce), dysprosium (Dy), erbium (Er),
europium (Eu), gadolinium (Gd), holmium (Ho),
lanthanum (La), lutetium (Lu), neodymium (Nd),
praseodymium (Pr), promethium (Pm), samarium
(Sm), scandium (Sc), terbium (Tb), thulium
(Tm), ytterbium (Yb), and yttrium (Y).
Despite their name, rare-earth elements are
– with the exception of the radioactive
promethium – relatively plentiful in Earth's
crust, with cerium being the 25th most abundant
element at 68 parts per million, more abundant
than copper.
However, because of their geochemical properties,
rare-earth elements are typically dispersed
and not often found concentrated in rare-earth
minerals; as a result economically exploitable
ore deposits are less common.
The first rare-earth mineral discovered (1787)
was gadolinite, a mineral composed of cerium,
yttrium, iron, silicon, and other elements.
This mineral was extracted from a mine in
the village of Ytterby in Sweden; four of
the rare-earth elements bear names derived
from this single location.
== List ==
A table listing the 17 rare-earth elements,
their atomic number and symbol, the etymology
of their names, and their main usages (see
also Applications of lanthanides) is provided
here.
Some of the rare-earth elements are named
after the scientists who discovered or elucidated
their elemental properties, and some after
their geographical discovery.
== Abbreviations ==
The following abbreviations are often used:
RE = rare earth
REM = rare-earth metals
REE = rare-earth elements
REO = rare-earth oxides
REY = rare-earth elements and yttrium
LREE = light rare-earth elements
HREE = heavy rare-earth elements
== 
Discovery and early history ==
The first rare-earth element discovered was
the black mineral "ytterbite" (renamed to
gadolinite in 1800).
It was discovered by Lieutenant Carl Axel
Arrhenius in 1787 at a quarry in the village
of Ytterby, Sweden.Arrhenius's "ytterbite"
reached Johan Gadolin, a Royal Academy of
Turku professor, and his analysis yielded
an unknown oxide (earth) that he called yttria.
Anders Gustav Ekeberg isolated beryllium from
the gadolinite but failed to recognize other
elements ore contained.
After this discovery in 1794 a mineral from
Bastnäs near Riddarhyttan, Sweden, which
was believed to be an iron–tungsten mineral,
was re-examined by Jöns Jacob Berzelius and
Wilhelm Hisinger.
In 1803 they obtained a white oxide and called
it ceria.
Martin Heinrich Klaproth independently discovered
the same oxide and called it ochroia.
Thus by 1803 there were two known rare-earth
elements, yttrium and cerium, although it
took another 30 years for researchers to determine
that other elements were contained in the
two ores ceria and yttria (the similarity
of the rare-earth metals' chemical properties
made their separation difficult).
In 1839 Carl Gustav Mosander, an assistant
of Berzelius, separated ceria by heating the
nitrate and dissolving the product in nitric
acid.
He called the oxide of the soluble salt lanthana.
It took him three more years to separate the
lanthana further into didymia and pure lanthana.
Didymia, although not further separable by
Mosander's techniques, was in fact still a
mixture of oxides.
In 1842 Mosander also separated the yttria
into three oxides: pure yttria, terbia and
erbia (all the names are derived from the
town name "Ytterby").
The earth giving pink salts he called terbium;
the one that yielded yellow peroxide he called
erbium.
So in 1842 the number of known rare-earth
elements had reached six: yttrium, cerium,
lanthanum, didymium, erbium and terbium.
Nils Johan Berlin and Marc Delafontaine tried
also to separate the crude yttria and found
the same substances that Mosander obtained,
but Berlin named (1860) the substance giving
pink salts erbium, and Delafontaine named
the substance with the yellow peroxide terbium.
This confusion led to several false claims
of new elements, such as the mosandrium of
J. Lawrence Smith, or the philippium and decipium
of Delafontaine.
Due to the difficulty in separating the metals
(and determining the separation is complete),
the total number of false discoveries was
dozens, with some putting the total number
of discoveries at over a hundred.
=== Spectroscopy ===
There were no further discoveries for 30 years,
and the element didymium was listed in the
periodic table of elements with a molecular
mass of 138.
In 1879 Delafontaine used the new physical
process of optical flame spectroscopy and
found several new spectral lines in didymia.
Also in 1879, the new element samarium was
isolated by Paul Émile Lecoq de Boisbaudran
from the mineral samarskite.
The samaria earth was further separated by
Lecoq de Boisbaudran in 1886, and a similar
result was obtained by Jean Charles Galissard
de Marignac by direct isolation from samarskite.
They named the element gadolinium after Johan
Gadolin, and its oxide was named "gadolinia".
Further spectroscopic analysis between 1886
and 1901 of samaria, yttria, and samarskite
by William Crookes, Lecoq de Boisbaudran and
Eugène-Anatole Demarçay yielded several
new spectroscopic lines that indicated the
existence of an unknown element.
The fractional crystallization of the oxides
then yielded europium in 1901.
In 1839 the third source for rare earths became
available.
This is a mineral similar to gadolinite, uranotantalum
(now called "samarskite").
This mineral from Miass in the southern Ural
Mountains was documented by Gustav Rose.
The Russian chemist R. Harmann proposed that
a new element he called "ilmenium" should
be present in this mineral, but later, Christian
Wilhelm Blomstrand, Galissard de Marignac,
and Heinrich Rose found only tantalum and
niobium (columbium) in it.
The exact number of rare-earth elements that
existed was highly unclear, and a maximum
number of 25 was estimated.
The use of X-ray spectra (obtained by X-ray
crystallography) by Henry Gwyn Jeffreys Moseley
made it possible to assign atomic numbers
to the elements.
Moseley found that the exact number of lanthanides
had to be 15, and that element 61 had yet
to be discovered.
Using these facts about atomic numbers from
X-ray crystallography, Moseley also showed
that hafnium (element 72) would not be a rare-earth
element.
Moseley was killed in World War I in 1915,
years before hafnium was discovered.
Hence, the claim of Georges Urbain that he
had discovered element 72 was untrue.
Hafnium is an element that lies in the periodic
table immediately below zirconium, and hafnium
and zirconium are very similar in their chemical
and physical properties.
During the 1940s, Frank Spedding and others
in the United States (during the Manhattan
Project) developed the chemical ion-exchange
procedures for separating and purifying the
rare-earth elements.
This method was first applied to the actinides
for separating plutonium-239 and neptunium
from uranium, thorium, actinium, and the other
actinides in the materials produced in nuclear
reactors.
The plutonium-239 was very desirable because
it is a fissile material.
The principal sources of rare-earth elements
are the minerals bastnäsite, monazite, and
loparite and the lateritic ion-adsorption
clays.
Despite their high relative abundance, rare-earth
minerals are more difficult to mine and extract
than equivalent sources of transition metals
(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 during the
late 1950s and early 1960s.Some ilmenite concentrates
contain small amounts scandium and other rare-earth
elements, which could be analysed by XRF .
=== Early classification ===
Before the time that ion-exchange methods
and elution were available, the separation
of the rare earths was primarily achieved
by repeated precipitation or crystallisation.
In those days, the first separation was into
two main groups, the cerium earths (scandium,
lanthanum, cerium, praseodymium, neodymium,
and samarium) and the yttrium earths (yttrium,
dysprosium, holmium, erbium, thulium, ytterbium,
and lutetium).
Europium, gadolinium, and terbium were either
considered as a separate group of rare-earth
elements (the terbium group), or europium
was included in the cerium group, and gadolinium
and terbium were included in the yttrium group.
The reason for this division arose from the
difference in solubility of rare-earth double
sulfates with sodium and potassium.
The sodium double sulfates of the cerium group
are difficultly soluble, those of the terbium
group slightly, and those of the yttrium group
are very soluble.
Sometimes, the yttrium group was further split
into the erbium group (dysprosium, holmium,
erbium, and thulium) and the ytterbium group
(ytterbium and lutetium), but today the main
grouping is between the cerium and the yttrium
groups.
Today, the rare-earth elements are classified
as light or heavy rare-earth elements, rather
than in cerium and yttrium groups.
=== Light versus heavy classification ===
The classification of rare-earth elements
is inconsistent between authors.
The most common distinction between rare-earth
elements is made by atomic numbers; those
with low atomic numbers are referred to as
light rare-earth elements (LREE), those with
high atomic numbers are the heavy rare-earth
elements (HREE), and those that fall in between
are typically referred to as the middle rare-earth
elements (MREE).
Commonly, rare-earth elements with atomic
numbers 57 to 61 are classified as light and
those with atomic numbers greater than 62
(corresponding to europium) are classified
as heavy-rare earth elements.
Increasing atomic numbers between light and
heavy rare-earth elements and decreasing atomic
radii throughout the series causes chemical
variations.
Europium is exempt of this classification
as it has two valence states: Eu+2 and Eu+3.
Yttrium is grouped as heavy rare-earth element
due to chemical similarities.The 1985 International
Union of Pure and Applied Chemistry “Red
Book” (p. 45) recommends that lanthanoid
is used rather than lanthanide.
The ending “-ide” normally indicates a
negative ion.
However, owing to wide current use, “lanthanide”
is still allowed and is roughly analogous
to rare earth element.
According to Professor of chemistry, Andrea
Sella, rare-earth elements differ from other
elements, insofar that "rare-earth metals,
when looked at anatomically, seem to be inseparable
from each other, in that they are all almost
exactly the same in terms of their chemical
properties.
However, in terms of their electronic properties,
their magnetic properties, each one is really
exquisitely unique, and so it can occupy a
tiny niche in our technology, where virtually
nothing else can."
For example, "the rare-earth elements Praseodymium
(Pr) and Neodymium (Nd) can both be embedded
inside glass and they completely cut-out the
glare from the flame when one is doing glass-blowing."
== Origin ==
Rare-earth elements, except scandium, are
heavier than iron and thus are produced by
supernova nucleosynthesis or by the s-process
in asymptotic giant branch stars.
In nature, spontaneous fission of uranium-238
produces trace amounts of radioactive promethium,
but most promethium is synthetically produced
in nuclear reactors.
Due to their chemical similarity, the concentrations
of rare earths in rocks are only slowly changed
by geochemical processes, making their proportions
useful for geochronology and dating fossils.
== Geological distribution ==
Rare-earth element cerium is actually the
25th most abundant element in Earth's crust,
having 68 parts per million (about as common
as copper).
Only the highly unstable and radioactive promethium
"rare earth" is quite scarce.
The rare-earth elements are often found together.
The longest-lived isotope of promethium has
a half-life of 17.7 years, so the element
exists in nature in only negligible amounts
(approximately 572 g in the entire Earth's
crust).
Promethium is one of the two elements that
do not have stable (non-radioactive) isotopes
and are followed by (i.e. with higher atomic
number) stable elements (the other being technetium).
During the sequential accretion of the Earth,
the dense rare-earth elements were incorporated
into the deeper portions of the planet.
Early differentiation of molten material largely
incorporated the rare-earths into Mantle rocks.
The high field strength and large ionic radii
of rare-earths make them incompatible with
the crystal lattices of most rock-forming
minerals, so REE will undergo strong partitioning
into a melt phase if one is present.
REE are chemically very similar and have always
been difficult to separate, but a gradual
decrease in ionic radius from LREE to HREE,
called lanthanide contraction, can produce
a broad separation between light and heavy
REE.
The larger ionic radii of LREE make them generally
more incompatible than HREE in rock-forming
minerals, and will partition more strongly
into a melt phase, while HREE may prefer to
remain in the crystalline residue, particularly
if it contains HREE-compatible minerals like
garnet.
The result is that all magma formed from partial
melting will always have greater concentrations
of LREE than HREE, and individual minerals
may be dominated by either HREE or LREE, depending
on which range of ionic radii best fits the
crystal lattice.Among the anhydrous rare-earth
phosphates, it is the tetragonal mineral xenotime
that incorporates yttrium and the HREE, whereas
the monoclinic monazite phase incorporates
cerium and the LREE preferentially.
The smaller size of the HREE allows greater
solid solubility in the rock-forming minerals
that make up Earth's mantle, and thus yttrium
and the HREE show less enrichment in Earth's
crust relative to chondritic abundance than
does cerium and the LREE.
This has economic consequences: large ore
bodies of LREE are known around the world
and are being exploited.
Ore bodies for HREE are more rare, smaller,
and less concentrated.
Most of the current supply of HREE originates
in the "ion-absorption clay" ores of Southern
China.
Some versions provide concentrates containing
about 65% yttrium oxide, with the HREE being
present in ratios reflecting the Oddo–Harkins
rule: even-numbered REE at abundances of about
5% each, and odd-numbered REE at abundances
of about 1% each.
Similar compositions are found in xenotime
or gadolinite.Well-known minerals containing
yttrium, and other HREE, include gadolinite,
xenotime, samarskite, euxenite, fergusonite,
yttrotantalite, yttrotungstite, yttrofluorite
(a variety of fluorite), thalenite, yttrialite.
Small amounts occur in zircon, which derives
its typical yellow fluorescence from some
of the accompanying HREE.
The zirconium mineral eudialyte, such as is
found in southern Greenland, contains small
but potentially useful amounts of yttrium.
Of the above yttrium minerals, most played
a part in providing research quantities of
lanthanides during the discovery days.
Xenotime is occasionally recovered as a byproduct
of heavy-sand processing, but is not as abundant
as the similarly recovered monazite (which
typically contains a few percent of yttrium).
Uranium ores from Ontario have occasionally
yielded yttrium as a byproduct.Well-known
minerals containing cerium, and other LREE,
include bastnäsite, monazite, allanite, loparite,
ancylite, parisite, lanthanite, chevkinite,
cerite, stillwellite, britholite, fluocerite,
and cerianite.
Monazite (marine sands from Brazil, India,
or Australia; rock from South Africa), bastnäsite
(from Mountain Pass, California, or several
localities in China), and loparite (Kola Peninsula,
Russia) have been the principal ores of cerium
and the light lanthanides.Enriched deposits
of rare-earth elements at the surface of the
Earth, carbonatites and pegmatites, are related
to alkaline plutonism, an uncommon kind of
magmatism that occurs in tectonic settings
where there is rifting or that are near subduction
zones.
In a rift setting, the alkaline magma is produced
by very small degrees of partial melting (<1%)
of garnet peridotite in the upper mantle (200
to 600 km depth).
This melt becomes enriched in incompatible
elements, like the rare-earth elements, by
leaching them out of the crystalline residue.
The resultant magma rises as a diapir, or
diatreme, along pre-existing fractures, and
can be emplaced deep in the crust, or erupted
at the surface.
Typical REE enriched deposits types forming
in rift settings are carbonatites, and A-
and M-Type granitoids.
Near subduction zones, partial melting of
the subducting plate within the asthenosphere
(80 to 200 km depth) produces a volatile-rich
magma (high concentrations of CO2 and water),
with high concentrations of alkaline elements,
and high element mobility that the rare-earths
are strongly partitioned into.
This melt may also rise along pre-existing
fractures, and be emplaced in the crust above
the subducting slab or erupted at the surface.
REE enriched deposits forming from these melts
are typically S-Type granitoids.Alkaline magmas
enriched with rare-earth elements include
carbonatites, peralkaline granites (pegmatites),
and nepheline syenite.
Carbonatites crystallize from CO2-rich fluids,
which can be produced by partial melting of
hydrous-carbonated lherzolite to produce a
CO2-rich primary magma, by fractional crystallization
of an alkaline primary magma, or by separation
of a CO2-rich immiscible liquid from.
These liquids are most commonly forming in
association with very deep Precambrian Cratons,
like the ones found in Africa and the Canadian
Shield.
Ferrocarbonatites are the most common type
of carbonatite to be enriched in REE, and
are often emplaced as late-stage, brecciated
pipes at the core of igneous complexes; they
consist of fine-grained calcite and hematite,
sometimes with significant concentrations
of ankerite and minor concentrations of siderite.
Large carbonatite deposits enriched in rare-earth
elements include Mount Weld in Australia,
Thor Lake in Canada, Zandkopsdrift in South
Africa, and Mountain Pass in the USA.
Peralkaline granites (A-Type granitoids) have
very high concentrations of alkaline elements
and very low concentrations of phosphorus;
they are deposited at moderate depths in extensional
zones, often as igneous ring complexes, or
as pipes, massive bodies, and lenses.
These fluids have very low viscosities and
high element mobility, which allows for crystallization
of large grains, despite a relatively short
crystallization time upon emplacement; their
large grain size is why these deposits are
commonly referred to as pegmatites.
Economically viable pegmatites are divided
into Lithium-Cesium-Tantalum (LCT) and Niobium-Yttrium-Fluorine
(NYF) types; NYF types are enriched in rare-earth
minerals.
Examples of rare-earth pegmatite deposits
include Strange Lake in Canada, and Khaladean-Buregtey
in Mongolia.
Nepheline syenite (M-Type granitoids) deposits
are 90% feldspar and feldspathoid minerals,
and are deposited in small, circular massifs.
They contain high concentrations of rare-earth-bearing
accessory minerals.
For the most part these deposits are small
but important examples include Illimaussaq-Kvanefeld
in Greenland, and Lovozera in Russia.Rare-earth
elements can also be enriched in deposits
by secondary alteration either by interactions
with hydrothermal fluids or meteoric water
or by erosion and transport of resistate REE-bearing
minerals.
Argillization of primary minerals enriches
insoluble elements by leaching out silica
and other soluble elements, recrystallizing
feldspar into clay minerals such kaolinite,
halloysite and montmorillonite.
In tropical regions where precipitation is
high, weathering forms a thick argillized
regolith, this process is called supergene
enrichment and produces laterite deposits;
heavy rare-earth elements are incorporated
into the residual clay by absorption.
This kind of deposit is only mined for REE
in Southern China, where the majority of global
heavy rare-earth element production occurs.
REE-laterites do form elsewhere, including
over the carbonatite at Mount Weld in Australia.
REE may also by extracted from placer deposits
if the sedimentary parent lithology contained
REE-bearing, heavy resistate minerals.In 2011,
Yasuhiro Kato, a geologist at the University
of Tokyo who led a study of Pacific Ocean
seabed mud, published results indicating the
mud could hold rich concentrations of rare-earth
minerals.
The deposits, studied at 78 sites, came from
"[h]ot plumes from hydrothermal vents pull[ing]
these materials out of seawater and deposit[ing]
them on the seafloor, bit by bit, over tens
of millions of years.
One square patch of metal-rich mud 2.3 kilometers
wide might contain enough rare earths to meet
most of the global demand for a year, Japanese
geologists report July 3 in Nature Geoscience."
"I believe that rare[-]earth resources undersea
are much more promising than on-land resources,"
said Kato.
"[C]oncentrations of rare earths were comparable
to those found in clays mined in China.
Some deposits contained twice as much heavy
rare earths such as dysprosium, a component
of magnets in hybrid car motors."
== Geochemistry applications ==
The application of rare-earth elements to
geology is important to understanding the
petrological processes of igneous, sedimentary
and metamorphic rock formation.
In geochemistry, rare-earth elements can be
used to infer the petrological mechanisms
that have affected a rock due to the subtle
atomic size differences between the elements,
which causes preferential fractionation of
some rare earths relative to others depending
on the processes at work.In geochemistry,
rare-earth elements are typically presented
in normalized "spider" diagrams, in which
concentration of rare-earth elements are normalized
to a reference standard and are then expressed
as the logarithm to the base 10 of the value.
Commonly, the rare-earth elements are normalized
to chondritic meteorites, as these are believed
to be the closest representation of unfractionated
solar system material.
However, other normalizing standards can be
applied depending on the purpose of the study.
Normalization to a standard reference value,
especially of a material believed to be unfractionated,
allows the observed abundances to be compared
to initial abundances of the element.
Normalization also removes the pronounced
‘zig-zag’ pattern caused by the differences
in abundance between even and odd atomic numbers.
The trends that are observed in "spider" diagrams
are typically referred to as "patterns", which
may be diagnostic of petrological processes
that have affected the material of interest.The
rare-earth elements patterns observed in igneous
rocks are primarily a function of the chemistry
of the source where the rock came from, as
well as the fractionation history the rock
has undergone.
Fractionation is in turn a function of the
partition coefficients of each element.
Partition coefficients are responsible for
the fractionation of a trace elements (including
rare-earth elements) into the liquid phase
(the melt/magma) into the solid phase (the
mineral).
If an element preferentially remains in the
solid phase it is termed ‘compatible’,
and it preferentially partitions into the
melt phase it is described as ‘incompatible’.
Each element has a different partition coefficient,
and therefore fractionates into solid and
liquid phases distinctly.
These concepts are also applicable to metamorphic
and sedimentary petrology.
In igneous rocks, particularly in felsic melts,
the following observations apply: anomalies
in europium are dominated by the crystallization
of feldspars.
Hornblende, controls the enrichment of MREE
compared to LREE and HREE.
Depletion of LREE relative to HREE may be
due to the crystallization of olivine, orthopyroxene,
and clinopyroxene.
On the other hand, depletion of HREE relative
to LREE may be due to the presence of garnet,
as garnet preferentially incorporates HREE
into its crystal structure.
The presence of zircon may also cause a similar
effect.In sedimentary rocks, rare-earth elements
in clastic sediments are a representation
provenance.
The rare-earth element concentrations are
not typically affected by sea and river waters,
as rare-earth elements are insoluble and thus
have very low concentrations in these fluids.
As a result, when a sediment is transported,
rare-earth element concentrations are unaffected
by the fluid and instead the rock retains
the rare-earth element concentration from
its source.Sea and river waters typically
have low rare-earth element concentrations.
However, aqueous geochemistry is still very
important.
In oceans, rare-earth elements reflect input
from rivers, hydrothermal vents, and aeolian
sources; this is important in the investigation
of ocean mixing and circulation.Rare-earth
elements are also useful for dating rocks,
as some radioactive isotopes display long
half-lives.
Of particular interest are the 138La-138Ce,
147Sm-143Nd, and 176Lu-176Hf systems.
== Global rare-earth production ==
Until 1948, most of the world's rare earths
were sourced from placer sand deposits in
India and Brazil.
Through the 1950s, South Africa was the world's
rare-earth source, from a monazite-rich reef
at the Steenkampskraal mine in Western Cape
province.
Through the 1960s until the 1980s, the Mountain
Pass rare earth mine in California was the
leading producer.
Today, the Indian and South African deposits
still produce some rare-earth concentrates,
but they are dwarfed by the scale of Chinese
production.
In 2017, China produced 81% of the world's
rare-earth supply, mostly in Inner Mongolia,
although it had only 36.7% of reserves.
Australia was the second and only other major
producer with 15% of world production.
All of the world's heavy rare earths (such
as dysprosium) come from Chinese rare-earth
sources such as the polymetallic Bayan Obo
deposit.
The Browns Range mine, located 160 km south
east of Halls Creek in northern Western Australia,
is currently under development and is positioned
to become the first significant dysprosium
producer outside of China.Increased demand
has strained supply, and there is growing
concern that the world may soon face a shortage
of the rare earths.
In several years from 2009 worldwide demand
for rare-earth elements is expected to exceed
supply by 40,000 tonnes annually unless major
new sources are developed.
In 2013, it was stated that the demand for
REEs would increase due to the dependence
of the EU on these elements, the fact that
rare earth elements cannot be substituted
by other elements and that REEs have a low
recycling rate.
Furthermore, due to the increased demand and
low supply, future prices are expected to
increase and there is a chance that countries
other than China will open REE mines.
REE is increasing in demand due to the fact
that they are essential for new and innovative
technology that is being created.
These new products that need REEs to be produced
are high technology equipment such as smart
phones, digital cameras, computer parts, etc.
In addition, these elements are more prevalent
in the following industries: renewable energy
technology, military equipment, glass making,
and metallurgy.
=== China ===
These concerns have intensified due to the
actions of China, the predominant supplier.
Specifically, China has announced regulations
on exports and a crackdown on smuggling.
On September 1, 2009, China announced plans
to reduce its export quota to 35,000 tons
per year in 2010–2015 to conserve scarce
resources and protect the environment.
On October 19, 2010, China Daily, citing an
unnamed Ministry of Commerce official, reported
that China will "further reduce quotas for
rare[-]earth exports by 30 percent at most
next year to protect the precious metals from
over-exploitation."
The government in Beijing further increased
its control by forcing smaller, independent
miners to merge into state-owned corporations
or face closure.
At the end of 2010, China announced that the
first round of export quotas in 2011 for rare
earths would be 14,446 tons, which was a 35%
decrease from the previous first round of
quotas in 2010.
China announced further export quotas on 14
July 2011 for the second half of the year
with total allocation at 30,184 tons with
total production capped at 93,800 tonnes.
In September 2011, China announced the halt
in production of three of its eight major
rare-earth mines, responsible for almost 40%
of China's total rare-earth production.
In March 2012, the US, EU, and Japan confronted
China at WTO about these export and production
restrictions.
China responded with claims that the restrictions
had environmental protection in mind.
In August 2012, China announced a further
20% reduction in production.
These restrictions have damaged industries
in other countries and forced producers of
rare-earth products to relocate their operations
to China.
The Chinese restrictions on supply failed
in 2012, as prices dropped in response to
the opening of other sources.
The price of dysprosium oxide was 994 USD/kg
in 2011, but dropped to US$265/kg by 2014.On
August 29, 2014, the WTO ruled that China
had broken free-trade agreements, and the
WTO said in the summary of key findings that
"the overall effect of the foreign and domestic
restrictions is to encourage domestic extraction
and secure preferential use of those materials
by Chinese manufacturers."
China declared that it would implement the
ruling on September 26, 2014, but would need
some time to do so.
By January 5, 2015, China had lifted all quotas
from the export of rare earths, however export
licences will still be required.
=== Outside of China ===
As a result of the increased demand and tightening
restrictions on exports of the metals from
China, some countries are stockpiling rare-earth
resources.
Searches for alternative sources in Australia,
Brazil, Canada, South Africa, Tanzania, Greenland,
and the United States are ongoing.
Mines in these countries were closed when
China undercut world prices in the 1990s,
and it will take a few years to restart production
as there are many barriers to entry.
One example is the Mountain Pass mine in California,
which announced its resumption of operations
on a start-up basis on August 27, 2012.
Other significant sites under development
outside of China include the Nolans Project
in Central Australia, the Bokan Mountain project
in Alaska, the remote Hoidas Lake project
in northern Canada, and the Mount Weld project
in Australia.
The Hoidas Lake project has the potential
to supply about 10% of the $1 billion of REE
consumption that occurs in North America every
year.
Vietnam signed an agreement in October 2010
to supply Japan with rare earths from its
northwestern Lai Châu Province.In the US,
NioCorp Development Ltd has raised $1.3 billion
in funding toward opening a niobium, scandium,
and titanium mine at its Elk Creek site in
southeast Nebraska which may be able to produce
as much as 7200 tonnes of ferro niobium and
95 tonnes of scandium dioxide annually.Also
under consideration for mining are sites such
as Thor Lake in the Northwest Territories,
and various locations in Vietnam.
Additionally, in 2010, a large deposit of
rare-earth minerals was discovered in Kvanefjeld
in southern Greenland.
Pre-feasibility drilling at this site has
confirmed significant quantities of black
lujavrite, which contains about 1% rare-earth
oxides (REO).
The European Union has urged Greenland to
restrict Chinese development of rare-earth
projects there, but as of early 2013, the
government of Greenland has said that it has
no plans to impose such restrictions.
Many Danish politicians have expressed concerns
that other nations, including China, could
gain influence in thinly populated Greenland,
given the number of foreign workers and investment
that could come from Chinese companies in
the near future because of the law passed
December 2012.In central Spain, Ciudad Real
Province, the proposed rare-earth mining project
'Matamulas' may provide, according to its
developers, up to 2,100 Tn/year (33% of the
annual UE demand).
However, this project has been suspended by
regional authorities due to social and environmental
concerns.
Adding to potential mine sites, ASX listed
Peak Resources announced in February 2012,
that their Tanzanian-based Ngualla project
contained not only the 6th largest deposit
by tonnage outside of China, but also the
highest grade of rare-earth elements of the
6.North Korea has been reported to have exported
rare-earth ore to China, about US$1.88 million
worth during May and June 2014.
Rare-earth elements may be a factor behind
the 2018 thaw in North Korea–United States
relations.
==== Malaysian refining plans ====
In early 2011, Australian mining company,
Lynas, was reported to be "hurrying to finish"
a US$230 million rare-earth refinery on the
eastern coast of Peninsular Malaysia's industrial
port of Kuantan.
The plant would refine ore — lanthanides
concentrate from the Mount Weld mine in Australia.
The ore would be trucked to Fremantle and
transported by container ship to Kuantan.
Within two years, Lynas was said to expect
the refinery to be able to meet nearly a third
of the world's demand for rare-earth materials,
not counting China.
The Kuantan development brought renewed attention
to the Malaysian town of Bukit Merah in Perak,
where a rare-earth mine operated by a Mitsubishi
Chemical subsidiary, Asian Rare Earth, closed
in 1992 and left continuing environmental
and health concerns.
In mid-2011, after protests, Malaysian government
restrictions on the Lynas plant were announced.
At that time, citing subscription-only Dow
Jones Newswire reports, a Barrons report said
the Lynas investment was $730 million, and
the projected share of the global market it
would fill put at "about a sixth."
An independent review initiated by the Malaysian
Government, and conducted by the International
Atomic Energy Agency (IAEA) in 2011 to address
concerns of radioactive hazards, found no
non-compliance with international radiation
safety standards.However, the Malaysian authorities
confirmed that as of October 2011, Lynas was
not given any permit to import any rare-earth
ore into Malaysia.
On February 2, 2012, the Malaysian AELB (Atomic
Energy Licensing Board) recommended that Lynas
be issued a Temporary Operating License (TOL)
subject to completion of a number of conditions.
On April 3, 2012, Lynas announced to the Malaysian
media that these conditions had been met,
and was now waiting on the issuance of the
licence.
On 2 September 2014, Lynas was issued a 2-year
Full Operating Stage License (FOSL) by the
Malaysian Atomic Energy Licensing Board (AELB).
=== Other sources ===
Significant quantities of rare-earth oxides
are found in tailings accumulated from 50
years of uranium ore, shale and loparite mining
at Sillamäe, Estonia.
Due to the rising prices of rare earths, extraction
of these oxides has become economically viable.
The country currently exports around 3,000
tonnes per year, representing around 2% of
world production.
Similar resources are suspected in the western
United States, where gold rush-era mines are
believed to have discarded large amounts of
rare earths, because they had no value at
the time.In May 2012, researchers from two
universities in Japan announced that they
had discovered rare earths in Ehime Prefecture,
Japan.In January 2013 a Japanese deep-sea
research vessel obtained seven deep-sea mud
core samples from the Pacific Ocean seafloor
at 5,600 to 5,800 meters depth, approximately
250 kilometres (160 mi) south of the island
of Minami-Tori-Shima.
The research team found a mud layer 2 to 4
meters beneath the seabed with concentrations
of up to 0.66% rare-earth oxides.
A potential deposit might compare in grade
with the ion-absorption-type deposits in southern
China that provide the bulk of Chinese REO
mine production, which grade in the range
of 0.05% to 0.5% REO.
==== Recycling ====
Another recently developed source of rare
earths is electronic waste and other wastes
that have significant rare-earth components.
New advances in recycling technology have
made extraction of rare earths from these
materials more feasible, and recycling plants
are currently operating in Japan, where there
is an estimated 300,000 tons of rare earths
stored in unused electronics.
In France, the Rhodia group is setting up
two factories, in La Rochelle and Saint-Fons,
that will produce 200 tons of rare earths
a year from used fluorescent lamps, magnets
and batteries.
Coal and coal by-products are a potential
source of critical elements including rare
earth elements (REE) with estimated amounts
in the range of 50 million metric tons.
== Uses ==
The uses, applications, and demand for rare-earth
elements has expanded over the years.
This is particularly due to the uses of rare-earth
elements in low-carbon technologies.
Some important uses of rare-earth elements
are applicable to the production of high-performance
magnets, catalysts, alloys, glasses, and electronics.
Nd is important in magnet production.
Rare-earth elements in this category are used
in the electric motors of hybrid vehicles,
wind turbines, hard disc drives, portable
electronics, microphones, speakers.
Ce and La are important as catalysts, and
are used for petroleum refining and as diesel
additives.
Ce, La and Nd are important in alloy making,
and in the production of fuel cells and Nickel-metal
hydride batteries.
Ce, Ga and Nd are important in electronics
and are used in the production of LCD and
plasma screens, fiber optics, lasers, as well
as in medical imaging.
Additional uses for earth elements are as
tracers in medical applications, fertilizers,
and in water treatment.REEs have been used
in agriculture to increase plant growth, productivity,
and stress resistance seemingly without negative
effects for human and animal consumption.
REEs are used in agriculture through REE-enriched
fertilizers which is a widely used practice
in China.
In addition, REEs are feed additives for livestock
which has resulted in increased production
such as larger animals and a higher production
of eggs and dairy products.
However, this practice has resulted in REE
bio-accumulation within livestock and has
impacted vegetation and algae growth in these
agricultural areas.
Additionally while no ill effects have been
observed at current low concentrations the
effects over the long term and with accumulation
over time are unknown prompting some calls
for more research into their possible effects.
== Environmental considerations ==
REEs are naturally found in very low concentration
in the environment.
Near mining and industrial sites the concentrations
can rise to many times the normal background
levels.
Once in the environment REEs can leach into
the soil where their transport is determined
by numerous factors such as erosion, weathering,
pH, precipitation, ground water, etc.
Acting much like metals they can speciate
depending on the soil condition being either
motile or adsorbed to soil particles depending
on conditions.
Depending on their bio-availability REEs can
be absorbed into plants and later consumed
by humans and animals.
Including the mining of REEs and REE-enriched
fertilizers, the production of phosphorus
fertilizers also contribute to REE contamination
due to their production and deposition around
the phosphorus fertilizer production plants.
Furthermore, strong acids are used during
the extraction process of REEs, which can
then leach out in to the environment and be
transported through water bodies and result
in the acidification of aquatic environments.
Another additive of REE mining that contributes
to REE environmental contamination is cerium
oxide (CeO2) which is produced during the
combustion of diesel and is released as an
exhaust particulate matter and contributes
heavily to soil and water contamination.
Mining, refining, and recycling of rare earths
have serious environmental consequences if
not properly managed.
A potential hazard could be low-level radioactive
tailings resulting from the occurrence of
thorium and uranium in rare-earth element
ores.
Improper handling of these substances can
result in extensive environmental damage.
In May 2010, China announced a major, five-month
crackdown on illegal mining in order to protect
the environment and its resources.
This campaign is expected to be concentrated
in the South, where mines – commonly small,
rural, and illegal operations – are particularly
prone to releasing toxic wastes into the general
water supply.
However, even the major operation in Baotou,
in Inner Mongolia, where much of the world's
rare-earth supply is refined, has caused major
environmental damage.
=== Consequences and remediation ===
The Bukit Merah mine in Malaysia has been
the focus of a US$100 million cleanup that
is proceeding in 2011.
After having accomplished the hilltop entombment
of 11,000 truckloads of radioactively contaminated
material, the project is expected to entail
in summer, 2011, the removal of "more than
80,000 steel barrels of radioactive waste
to the hilltop repository."In May 2011, after
the Fukushima Daiichi nuclear disaster, widespread
protests took place in Kuantan over the Lynas
refinery and radioactive waste from it.
The ore to be processed has very low levels
of thorium, and Lynas founder and chief executive
Nicholas Curtis said "There is absolutely
no risk to public health."
T. Jayabalan, a doctor who says he has been
monitoring and treating patients affected
by the Mitsubishi plant, "is wary of Lynas's
assurances.
The argument that low levels of thorium in
the ore make it safer doesn't make sense,
he says, because radiation exposure is cumulative."
Construction of the facility has been halted
until an independent United Nations IAEA panel
investigation is completed, which is expected
by the end of June 2011.
New restrictions were announced by the Malaysian
government in late June.IAEA panel investigation
is completed and no construction has been
halted.
Lynas is on budget and on schedule to start
producing 2011.
The IAEA report has concluded in a report
issued on Thursday June 2011 said it did not
find any instance of "any non-compliance with
international radiation safety standards"
in the project.If the proper safety standards
are followed, REE mining is relatively low
impact.
Molycorp (before going bankrupt) often exceeded
environmental regulations to improve public
image.
=== Environmental pollution ===
Literature published in 2004 suggests that
along with previously established pollution
mitigation, a more circular supply chain would
help mitigate some of the pollution that the
extraction point.
This means recycling and reusing REEs that
are already in use or reaching the end of
their life cycle.
==== Impact on vegetation ====
The mining of REEs have caused the contamination
of surrounding soil and water of these production
areas, which has impacted vegetation in these
area by decreasing chlorophyll production
which affects photosynthesis and inhibits
the growth of the plants.
However, the impact of REE contamination on
vegetation is dependent on the plants present
in the contaminated environments because there
are some plants that do retain and absorb
REEs and there are some that don't.
Also, the ability for the vegetation to intake
the REE is dependent on the type of REE present
in the soil, hence there are a multitude of
factors that influence this process.
Agricultural plants are the main type of vegetation
affected by REE contamination in the environment.
Also, the main two plants that have a higher
chance of absorbing and storing REEs are apples
and beets.
Furthermore, there is a possibility that the
REE that can leach out into aquatic environments
and can be absorbed by aquatic vegetation,
which can then bio-accumulate and potentially
enter the human food-chain if livestock or
humans choose to eat the vegetation.
An example of this situation was the case
of the water hyacinth (Eichhornia crassipes)
in China, where the water was contaminated
due to a REE-enriched fertilizer being used
in an agricultural area of close proximity.
This led to the nearby aquatic environment
becoming contaminated with Cerium and resulted
in the water hyacinth becoming three times
more concentrated in Cerium than its surrounding
water.
==== Impact on human health ====
REEs are a large group with many different
properties and levels in the environment,
because of this, and limited research, it
has been difficult to determine safe levels
of exposure for humans.
A number of studies have focused on risk assessment
based on routes of exposure and divergence
from back ground levels related to nearby
agriculture, mining, and industry.
It has been demonstrated that numerous REEs
have toxic properties and are present in the
environment or in work places.
Exposure to these can lead to a wide range
of negative health outcomes such as cancer,
respiratory issues, dental loss including
death.
However these elements are numerous and present
in many different forms and at different levels
of toxicity, as such it has been difficult
to give blanket warnings on cancer risk and
toxicity as some of these are harmless while
others pose a risk.What toxicity is shown
appears to be at very high levels of exposure
through ingestion of contaminated food and
water, through inhalation of dust/smoke particles
either as an occupational hazard or due to
proximity to contaminated sites such as mines
and cities.
Therefore, the main issues that these residents
would face is bioaccumulation of REEs and
the impact on their respiratory system but
overall, there can be other possible short
term and long term health effects.
It was found that people living near mines
in China had many times the levels of REEs
in their blood, urine, bone and hair compared
to controls far from mining sites.
This higher level was related to the high
levels of REEs present in the vegetables they
cultivated, the soil, and the water from the
wells indicating that the high levels were
caused by the nearby mine.
While REE levels varied between men and women
the group most at risk were children because
REEs can impacted the neurological development
of children.
Hence, it can impact their IQ and can cause
memory loss.Residents blamed a rare-earth
refinery at Bukit Merah for birth defects
and eight leukemia cases within five years
in a community of 11,000 — after many years
with no leukemia cases.
Seven of the leukemia victims died.
Osamu Shimizu, a director of Asian Rare Earth,
said "the company might have sold a few bags
of calcium phosphate fertilizer on a trial
basis as it sought to market byproducts; calcium
phosphate is not radioactive or dangerous"
in reply to a former resident of Bukit Merah
who said that "The cows that ate the grass
[grown with the fertilizer] all died."
Malaysia's Supreme Court ruled on 23 December
1993 that there was no evidence that the local
chemical joint venture Asian Rare Earth was
contaminating the local environment.
==== Impact on animal health ====
Experiments exposing rats to various cerium
compounds have found accumulation primarily
in the lungs and liver.
This resulted in various negative health outcomes
associated with those organs.
REEs have been added to feed in livestock
to increase their body mass and increase milk
production.
They are most-commonly used to increase the
body mass of pigs and it was discovered that
REEs increase the digestibility and nutrient
use of pigs digestive system.
Studies point to a dose response when considering
toxicity versus positive effects.
While small doses in the environment and properly
administered seem to have no ill effects.
Larger doses have been shown to have negative
effects specifically in the organs where they
accumulate.
The process mining of REEs in China has resulted
in soil and water contamination in certain
areas, which has then transported through
these systems and in these aquatic bodies,
it could potentially bio-accumulate within
aquatic biota.
Furthermore, in some cases animals that live
in the REE contaminated areas have been diagnosed
with organ or system problems.
Furthermore, REEs have been used in freshwater
fish farming by allowing the fish to consume
the REE because it protects the fish from
possible diseases.
One main reason why they have been avidly
used in animal livestock feeding is that they
have had better results than inorganic livestock
feed enhancers.
== Geo-political considerations ==
China has officially cited resource depletion
and environmental concerns as the reasons
for a nationwide crackdown on its rare-earth
mineral production sector.
However, non-environmental motives have also
been imputed to China's rare-earth policy.
According to The Economist, "Slashing their
exports of rare-earth metals… is all about
moving Chinese manufacturers up the supply
chain, so they can sell valuable finished
goods to the world rather than lowly raw materials."
Furthermore, China currently has an effective
monopoly on the world's REE Value Chain. (all
the refineries and processing plants that
transform the raw ore into valuable elements).
In the words of Deng Xiaoping, a Chinese politician
from the late 1970s to the late 1980s, "The
Middle East has oil; we have rare earths ... it
is of extremely important strategic significance;
we must be sure to handle the rare earth issue
properly and make the fullest use of our country's
advantage in rare earth resources."One possible
example of market control is the division
of General Motors that deals with miniaturized
magnet research, which shut down its US office
and moved its entire staff to China in 2006
(it should be noted that China's export quota
only applies to the metal but not products
made from these metals such as magnets).
It was reported, but officially denied, that
China instituted an export ban on shipments
of rare-earth oxides (but not alloys) to Japan
on 22 September 2010, in response to the detainment
of a Chinese fishing boat captain by the Japanese
Coast Guard.
On September 2, 2010, a few days before the
fishing boat incident, The Economist reported
that "China...in July announced the latest
in a series of annual export reductions, this
time by 40% to precisely 30,258 tonnes."The
United States Department of Energy in its
2010 Critical Materials Strategy report identified
dysprosium as the element that was most critical
in terms of import reliance.A 2011 report
"China's Rare-Earth Industry", issued by the
US Geological Survey and US Department of
the Interior, outlines industry trends within
China and examines national policies that
may guide the future of the country's production.
The report notes that China's lead in the
production of rare-earth minerals has accelerated
over the past two decades.
In 1990, China accounted for only 27% of such
minerals.
In 2009, world production was 132,000 metric
tons; China produced 129,000 of those tons.
According to the report, recent patterns suggest
that China will slow the export of such materials
to the world: "Owing to the increase in domestic
demand, the Government has gradually reduced
the export quota during the past several years."
In 2006, China allowed 47 domestic rare-earth
producers and traders and 12 Sino-foreign
rare-earth producers to export.
Controls have since tightened annually; by
2011, only 22 domestic rare-earth producers
and traders and 9 Sino-foreign rare-earth
producers were authorized.
The government's future policies will likely
keep in place strict controls: "According
to China's draft rare-earth development plan,
annual rare-earth production may be limited
to between 130,000 and 140,000 [metric tons]
during the period from 2009 to 2015.
The export quota for rare-earth products may
be about 35,000 [metric tons] and the Government
may allow 20 domestic rare-earth producers
and traders to export rare earths."The United
States Geological Survey is actively surveying
southern Afghanistan for rare-earth deposits
under the protection of United States military
forces.
Since 2009 the USGS has conducted remote sensing
surveys as well as fieldwork to verify Soviet
claims that volcanic rocks containing rare-earth
metals exist in Helmand province near the
village of Khanneshin.
The USGS study team has located a sizable
area of rocks in the center of an extinct
volcano containing light rare-earth elements
including cerium and neodymium.
It has mapped 1.3 million metric tons of desirable
rock, or about 10 years of supply at current
demand levels.
The Pentagon has estimated its value at about
$7.4 billion.
== See also ==
Group 3 element
Regolith-hosted rare earth element deposits
KREEP
Rare earth mineral
