Rare Earth Elements

Rare earth elements (REE’s) are a collection of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium. These are divided into two groups:

Light rare earth elements (LREE’s): Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Samarium (Sm) and Scandium (Sc).
 
Heavy rare earth elements (HREE’s): Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm) Ytterbium (Yb), Lutetium (Lu) and Yttrium (Y).

The elements are found as either oxides, carbonates or phosphates but usually all referred to as rare earth oxides (REO’s) and may be described as total rare earth oxides (TREO’s), heavy rare earth oxides (HREO’s) or light rare earth oxides (LREO’s) as appropriate.

Rare earth oxides can be found in a variety of minerals, but the most abundant rare earth oxides are found primarily in bastnaesite and monazite ores. Bastnaesite typically contains light rare earths and a small amount of the heavies, while monazite also contains mostly the light, but the fraction of the heavy rare earths is two to three times larger.

According to the U.S. Geological Survey, bastnaesite deposits in China and the U.S. make up the largest percentage of economic rare earth resources. Monazite deposits, found in Australia, Brazil, China, India, Malaysia, South Africa, Sri Lanka, Thailand, and the U.S. make up the second largest segment. Other examples of mineral ores known to contain rare earth elements include apatite, cheralite, eudialyte, loparite, phoshporites, rare-earth-bearing (ion absorption) clays, secondary monazite, spent uranium solutions, and xenotime.

Production

Despite their name rare earth elements are relatively plentiful in the Earth’s crust. However because of their geochemical properties REE’s are typically dispersed and not often found in economic quantiites. There are 2 projects outside of China that are presently being developed and under construction:

Mountain Pass (California, USA): This is a bastnaesite ore deposit which was mined into the 90’s. It has a resource of over 20 Mt of ore grading approx. 8.2% REO. The HREO/TREO ratio is 0.56% and Dy2O3 grade is nil.   US$500 million has been raised to reopen the mine and construction commenced in January 2011. It is planned to resume mining in 2012 at the rate of 1000 tons of ore per day, enough to produce 20,000 tonne of REO.

Mount Weld (Australia): This is a weathered monazite ore in the Central Lanthanide Deposit and a churchite, xenotime and secondary monazite ore in the Duncan Deposit. The recently upgraded resources are:   Central Lanthanide Deposit - resource of 9.88 Mt of ore grading 10.7% REO (HREO/TREO ratio is 3.46%); Duncan Deposit - resource of 7.62 Mt of grading 4.8% REO (HREO/TREO ratio is 10.85%).