Where are Rare Earth Elements Found?
Several years ago, Thermo Fisher Scientific answered the question “What’s So Rare About Rare Earth Elements?” As they noted, although originally thought to be rare, many of the Rare Earth Element (REE) minerals are actually common in the Earth’s crust. However, these elements rarely exist in pure form; they are usually found within other minerals, making them difficult to extract from the ore and costly to mine.
According to the USGS Rare Earths Report, the principal economic sources of rare earths are the minerals bastnasite, monazite, and loparite and the lateritic ion-adsorption clays. The elements range in crustal abundance from cerium, the 25th most abundant element of the 78 common elements in the Earth’s crust at 60 parts per million, to thulium and lutetium, the least abundant rare-earth elements at about 0.5 part per million.
When it comes to world resources, the USGS reported that “Resources are primarily in four geologic environments: carbonatites, alkaline igneous systems, ion-adsorption clay deposits, and monazite-xenotime-bearing placer deposits. Carbonatites and placer deposits are the leading sources of production of light rare-earth elements. Ion-adsorption clays are the leading source of production of heavy rare-earth elements.”
In the past, these rare earth elements were not considered to be mining-worthy, but because they are used in the ever-growing supply of technological devices, those thoughts have changed. REEs are commonly used in consumer electronics such as televisions, tablet computers, cameras, and mobile phones, as well as automobile catalytic converters and rechargeable batteries due to their unique optical and magnetic properties. They are also known as the “Green Elements” because they are essential to many green energy technologies. With the growing popularity of hybrid cars and other green products, rare earth elements are becoming more and more important to manufacturing. (Take a look at this infographic for a quick peek at the many ways rare earth elements are used.)
Geochemical exploration is the main method of REE mining. Mineral & Rare Earth Elements Analysers utilising XRF technology are very useful tools to qualitatively and quantitatively evaluate REE projects in real time in the field. Portable XRF instruments can provide real-time, on-site assays of REEs and other elements in any type of geological samples, including elements associated with REE-bearing minerals. By using the concentrations from these elements, it is possible to infer concentrations of heavy REEs (HREEs) that are commonly associated with host minerals.
Researchers continue to develop new technologies to recover rare earth elements (REEs). X-ray fluorescence technology is also an important tool in the rare earth element recycling industry because handheld XRF analysers can help detect lead, mercury, and cadmium in electronics such as printed circuit board (PCB) finishes, leads, terminations, solder and internal/external interconnects, keeping these toxic metals out of the recycling stream and future products. XRF analysers are also used to positively identify the chemical composition of numerous metal alloys.
Several new REE recycling technologies have been developed, including ones that involve using a nano-filtration system to extract and separate rare earth metals from phosphoric acid and waste, and using a combination of hollow fibre membranes, organic solvents, and neutral extractants to selectively recover rare earth elements. You can read about them in our previous blog Potential New Rare Earth Elements Supply from Phosphoric Acid