Mineralogy

Due to their very similar physical and chemical properties the different rare earth elements (REE) occur together and are recovered from their mineral host as a mixture of REE. Subsequent sequential chemical processing to separate and concentrate individual REE to high levels of purity is additional cost. In most deposits, the balance is tipped toward the light rare earth elements (LREE) which comprise 97-99% of resources. Deposits having an unusual balance with a high proportion of heavy rare earth elements (HREE) are very rare. Consequently, HREE are much more valuable.

Commercially, the three main REE ore mineral species are: bastnaesite, a LREE fluorocarbonate; monazite, a light/heavier rare earth phosphate that also contains radioactive thorium; and xenotime, the HREE yttrium phosphate.

Bastnaesite deposits in China and the USA constitute the largest percentage of the world’s rare earth reserves, while monazite deposits in Australia, Brazil, China, India, Malaysia, South Africa, Sri Lanka, Thailand, and the United States constitute the second largest segment. Other sources include apatite, cheralite, eudialyte, loparite, phosphorites, rare earth bearing (ion adsorption) clays, secondary monazite, and spent uranium solutions.