We have often written about Rare Earth Element (REE) minerals and how they are actually common in the Earth’s crust. However, despite their relatively high quantities, REEs are rarely concentrated into mineable ore deposits. In fact, REE ores are mineralogically and chemically complex. Thus, REE mining is challenging because they are abundant in more than one mineral, and each mineral requires a different and costly extraction technology and mineral processing technique.
Another hurdle: REE ores often contain thorium (Th), a radioactive element that creates radioactive waste and causes an additional cost of handling and processing.
So how can mining operators accurately assess the viability of deposits, respectively targeting REE-rich areas for extraction – especially if the areas to be mined are in remote locations and labs are not onsite?
First let’s go over the basics of REE themselves. Rare earth elements include, according to the nomenclature of the International Union of Pure and Applied Chemistry (IUPAC)1 , scandium (Sc), yttrium (Y) and the lanthanide series of elements, i.e. elements in the periodic table from lanthanum (La), atomic number 57 to lutetium (Lu), atomic number 71.
So mining operators need to map areas and analyze geological samples before digging in. Often used is a portable XRF analyzer with technology that covers an elemental range from magnesium to uranium, including light REEs, i.e.lanthanum (La), cerium (Ce), prasaeodymium (Pr) and Neodymium as well as scandium (Sc) and yttrium (Y). Usually, these elements occur in the same ore deposits as heavy REEs, making it possible to infer concentrations of heavier REEs from measured yttrium and scandium values.
X-ray fluorescence spectroscopy (XRF) is a non-destructive analytical technique used to determine the elemental composition of materials. XRF analyzers work by measuring the fluorescent (or secondary) X-rays emitted from a sample when excited by a primary X-ray source. Each of the elements present in a sample produces a set of characteristic fluorescent X-rays, or “unique fingerprints.” These fingerprints are distinct for each element, making XRF analysis an excellent tool for quantitative and qualitative measurements.
Handheld XRF analyzers are a reliable method to analyze ore samples in open pits and underground mines – achieving the accuracy required to provide defensible information for process oversight, quality assurance, and various other operational decisions (such as grade control). Portable XRF technology can help ascertain the viability of lower grade resources and find localized high-grade enrichments, delineate ore from waste boundaries to reduce the randomness of digging, and obtain defensible data and minimize the need to send samples to external testing labs.
Samples of the targeted areas are taken and pulverized to a typical particle size of less than 250 µm and introduced into sample cups fitted with 4µm polypropylene film. Then, analysis is executed using the XRF technology to measure REE and concomitant elements from magnesium to uranium.
This technology helps empower geologists and miners to target elements in complex minerals and is a vital tool to guide REE extraction, find high-grade enrichments, and ascertain the viability of low-grade ores during the mining process, considerably reducing lab analysis costs. The ability to localize anomalies and identify drilling targets helps enable mine operators to make informed decisions and accelerate REE exploration.
According to the US Geological Survey, limited quantities of rare earths are recovered from batteries, permanent magnets, and fluorescent lamps. As a result, without this ability to profitably mine REEs, we would not have many items we use every day, or they would be much more costly, including permanent magnets, industrial and automotive catalysts, glass polishing powders, glass additives, metals and alloys, battery alloys, ceramics, pigments, or phosphors – all of which require rare earth elements. In additional, various technologies use these materials in renewable energies, low energy lighting, emission control, electronics, medical, military, lasers, superconductors, and many other high-tech applications.
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References and Additional Resources
- Neil G. Connelly et al, Nomenclature of inorganic chemistry: IUPAC recommendations 2005. The red book. Royal Society of Chemistry, Cambridge, UK
- Rare Earth Element Fact Sheet, Natural Resources Canada