The rare earth elements (REEs) are the 15 lanthanides of the periodic table of elements, but often scandium and yttrium are included in the definition due to their similar chemical behaviour. The importance of this group of elements has grown in recent years due to use in a variety of industrial applications but particularly electronics, clean energy, and automobiles. Rare earth elements are found in two types of deposits: primary magmatic deposits and secondary concentration deposits, either by mechanical or chemical weathering.
The main minerals that are mined for REEs are bastnasite, monazite, loparite and laterite clays. All but the laterite clays are highly resistant to acid digestion, therefore necessitating a fusion decomposition for analysis.
ALS method ME-MS81h is suitable for ore grade REEs and is provided from a lithium borate fusion with ICP-MS analysis. The upper limit for the trace elements by this method range from 5,000 to 50,000 ppm, however, over-range analysis by ME-OGREE can determine concentrations up to 30%. Alternatively, where the lower detection limit is of lesser concern, fusion-XRF method ME_XRF30, which also includes loss on ignition as part of the analysis, may be suitable.
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|Loss on Ignition|| Furnace or Thermogravimetric Analyser (TGA).
Many of the minerals that host REEs are resistant to acid digestion, even the aggressive four-acid combination used for “near total” digestion. The results of an acid digestion can therefore underestimate the concentration of REEs if they are hosted in these resistant minerals because the elements are not taken into solution for measurement.
Where lower detection limits are required, two methods are suitable: ME-MS89L™ for trace values from a sodium peroxide fusion, or ME-MS81 from lithium borate.MORE INFORMATION