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Heavy rare earths, or HREEs, have higher-than-normal magnetic qualities and are very energy intensive. They are also more valuable than other rare earth metals because they are less common and are more complex to mine.
Rare earth metals can be divided into groups: light, middle and heavy. Heavy rare earths, or HREEs, have higher-than-normal magnetic qualities and are very energy intensive. They are also more valuable than other rare earth metals because they are less common and more complex to mine.
A recent Goldman Sachs report states that HREEs are expected to remain in deficit and therefore become even more valuable. While China and other rare earth-producing countries will have a surplus of light rare earth elements from 2013 onwards, the world will see a shortage of heavy rare earths, the report notes.
HREEs are lanthanide elements that have a higher atomic number, making them heavier, Alkane Resources (ASX:ALK), an Australia-focused exploration company, explains on its website. These elements are europium, gadolinium, dysprosium, holmium, erbium, thulium, terbium, ytterbium and lutetium. However, yttrium is also considered a HREE because its chemical makeup is similar to other heavy rare earths.
The total grade of a rare earth deposit, which is expressed as total rare earth oxide percentage (percent TREO), also distinguishes “heavy” rare earths. The TREO can be divided into light rare earth grade and heavy rare earth grade (percent HREO). Namibia Rare Earths (TSX:NRE), a Canadian company focused on rare earth projects in Namibia, offers an example. If the TREO is 2 percent and the HREO is 0.2 percent, the degree of heavy rare earth enrichment would be 10 percent. When the enrichment percentage is 10 or above, the rare earth deposit will be considered to be heavy or “enriched by heavies.”
HREE mining
The majority of heavy rare earth metals are mined in China, where rare earth oxides have been mined very cheaply, according to Navigator Resources (ASX:NAV). These rare earth oxides are found in rich clays in southern China. Inner Mongolia’s Bayan Obo project also produces rare earth oxides as a by-product of iron. In 2002, China was producing about 95 percent of the world’s rare earth oxides.
However, historically, rare earth metals were mined elsewhere, in countries including Brazil, India and Malaysia. Most of these metals were light, however, as high demand for heavy rare earth metals did not exist at the time. But when China uncovered large supplies of heavy rare earth oxides, interest in the metals sparked; the Asian country has remained a key supplier of HREEs and other rare earths.
Namibia is also home to current HREE mining. Namibia Rare Earths (TSX:NRE) operates the Lofdal rare earth project in northwestern Namibia, where heavy rare earth enrichment has been discovered. According to the company, the project site has certain zones where heavy rare earth enrichment is the highest in the world.
Ucore Rare Metals (TSXV:UCU) is a junior exploration company with rare earth projects in Alaska, making the United States another place where HREEs are mined. The company recently announced that its Alaska project boasts the highest grade of compliant heavy rare earth resource in the US. The project mainly focuses on HREE mining.
“They [heavy rare earths] are by far the most valuable of the class,” said Jim McKenzie, Ucore CEO.
Applications for HREEs
Yttrium: this HREE is mostly used to make phosphors that produce the red color in television screens. Hundreds of thousands of pounds of yttrium oxide are used for this application, according to LiveScience.
However, there are various other applications of the heavy rare earth metal, including using it to make microwave filters or as an additive in alloys to increase the strength of aluminum and magnesium alloys.
The radioactive isotope, yttirum-90, can be applied to making needles surgeons use to kill pain-transmitting nerves in the spinal cord.
Terbium: This HREE is the first member of the heavy group of rare earths, according to REE Handbook. The HREE can be applied to create terbium phosphors used in flat screen displays or trichromatic florescent bulbs and tubes. The rare earth is also used to intensify X-ray screens. Terbium can also be applied to a coating mixed with iron and cobalt to use on CDs and DVDs for data storage.
When terbium is combined with zirconium dioxide, it becomes a crystal stabilizer of elevated fuel cells, LiveScience reported.
Dysprosium: The second member of the heavy-group rare earth elements, dysprosium has two paired electrons that make it possible to detect radiation and improve permanent magnets. For example, when dysprosium is added to neodymium-iron-boron magnets, it increases the magnet’s operating temperature range for use in hybrid and electric cars.
The element is used in sonar sensor production, for positioning actuators, active noise and vibration cancelation, seismic waves and for tool machining, REE Handbook reported.
Another interesting application of dysprosium is using it in injections for rheumatoid arthritis patients.
Holmium: This HREE has three electron pairs giving it the ability to be a leading medical laser, REE Handbook said. It can also be used to detect objects based on vibrational signals, generate high-energy laser pulses and defeat infrared heat-seeking missiles.
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