Rare earths constitute the 15 lanthanide elements in the periodic table plus yttrium, a naturally associated mineral.
Rare earths are relatively abundant in the Earths crust, but do not often occur in minable concentrations.
World resources are contained primarily in bastnäsite and monazite. Bastnäsite deposits in China and the US constitute the largest percentage of the worlds rareearth economic resources, while monazite deposits constitute the second largest segment.
Apatite, cheralite, eudialyte, loparite, phosphorites, rare-earth-bearing (ion adsorption) clays, secondary monazite, spent uranium solutions and xenotime make up most of the remaining resources.
Rare earths have a wide range of applications from polishing powders to high-strength magnets, and are critical to environmental technologies such as electric vehicle motors and wind turbines, defence applications, and high-tech products such as smart phones.
The elements can be split into two groups: light rare earths and heavy rare earths, with the former generally occurring in much higher concentrations in the world
The main traded light rare earths elements are: lanthanum, cerium, praseodymium, neodymium and samarium.
The main traded heavy rare earth elements are: europium, gadolinium, terbium, dysprosium and erbium. Yttrium is usually grouped with the heavy elements.Supply
Throughout the 1990s and 2000s, rare earths production has been increasingly dominated by China, which now accounts for over 95% of global output.
Based in Inner Mongolia, Baotou Steel Rare Earth High-Tech Co. is Chinas largest player, producing around 55,000 tpa of light rare earths from its Bayan Obo mine.
Heavy rare earths and yttrium are largely extracted from ionic adsorption clays in Jiangxi and surrounding southern provinces, producing about 36,000 tpa.
However Chinas decision to begin limiting exports in the minerals in 2005 has led to a gradual reduction in commercially available rare earth products, and has spurred a frenzy of exploration activity in other parts of the world.
Among those attempting to fill the supply gap left by China, two of the most advanced developers are the US company Molycorp Inc., which is developing the Mountain Pass mine in California, US, and the Australian firm Lynas Corp. which owns the Mount Weld mine in Western Australia.
Other projects of note that are still at an early stage of development include the Dubbo Zirconia (and rare earths) project in Australia, owned by Alkane Resources Ltd; the Browns Range heavy rare earths project, also in Australia, owned by Northern Minerals Ltd; the Bokan Mountain project in Alaska owned by Ucore Rare Metals Inc.; the Kipawa heavy rare earth project in Canada owned by Matamec Explorations Inc.; and the Norra Karr heavy rare earths project in Sweden, owned by Tasman Metals Ltd.
Global rare earth oxide (REO) production in 2012 was estimated to be about 110,000 tonnes, according to the US Geological Survey (USGS).
Rare earths provide essential properties for a large number of hi-tech industries and are increasingly important in green energy technologies and consumer electronics.
The largest growth sector is expected to be for high-strength permanent magnets, including neodymium-iron-boron (Nd-Fe-B) and samarium cobalt (Sm-Co) magnets.
Nd-Fe-B magnets not only use neodymium but also the heavy rare earth element, dysprosium, and no substitute has been found for either raw material.
High-strength magnets are used in critical environmental and defence technologies including wind turbine motors, missiles, guidance systems as well as disk drives for computers and portable electronics.
The most common and lowest value rare earth element, cerium, is commonly used in polishing powders for high-value glass such as that used in televisions and computer screens.
The phosphorescent properties of rare earths including yttrium, europium and lanthanum are also central to plasma television and computer technology. They are also used in energy-saving light bulbs and x-rays.
Other applications are in metal alloys, ceramics, glass, lasers and fibre optics.
A price spike in 2011 caused by panic-buying in response to concerns over supply security of the minerals has led to many rare earth consumers using substitute raw materials, which has dented the rare earths market.
Prices fell more than 50% in 2012, and lacklustre demand caused major producers like Baotou Steel Rare Earth Hi-Tech to register huge falls in profits compared with 2011.
Due to the volumes used in hi-tech industries, Japan is the worlds largest importer of the materials, followed by the EU and the US.