Process overview -- how do you get the good stuff from the dirt?
Rare earth supply chain overview: While rare earth products have a variety of uses in advanced technology applications from renewable energy to smart phones, there is a process that must occur to get them from the mine to the end-product. Rare earths are not actually rare in terms of the frequency in which they are encountered. Instead, the moniker comes from the fact that is challenging and costly to isolate the elements and get them into useful concentrations.
Step #1- Mining Operations: The initial step in rare earth production is mining the ore. The ore contains mineral deposits such as bastnasite and monazite, which are what actually contain the rare earth elements. The ore is removed from the ground using traditional mining methods and is then crushed into gravel-sized
pieces to separate the bastnasite/monazite out of the rest of the material.
Step #2 – Milling: The milling step involves grinding the bastnasite pieces into fine particles of less than 1mm in size and then applying separation techniques in order to obtain viable concentrations of the rare earth material. MCP uses a flotation separation process in its operations. A flotation technique typically involves an agent being combined with the ground bastnasite while air is pushed through the bottom of a tank which causes the useful ore to be suspended on the surface while waste material sinks below. The resulting material is five or more times more concentrated then the originally mined ore.
Step #3 – Chemical Treatment and Concentrate Production. The mineral material from the milling process is then chemically treated through a process called “cracking,” which in MCP’s case uses hydrochloric acid. This allows the rare earth elements in the mineral to dissolve for further separation. The output is known as “concentrate” and is often a mix of many rare earth elements. For MCP there will be higher concentrations of cerium and lanthanum given their higher concentrations in its ore. The concentrate
can be sold on its own or it can be further processed to create higher purity products known as oxides.
Step #4 – Oxide Conversion: Additional chemical treatment is conducted in order to separate the rare earth elements from the concentrate into their own individual oxides at purities of 99.9% or greater. This is typically done via ion-exchange or multi-stage solvent extraction by targeting the different atomic weights of
each element in the concentrate. Oxide materials can be highly specialized to customer requirements and thus command much higher prices than concentrate.
Step #5 –Metal/Alloy Production: Certain applications require even higher purities than those found in oxides (think 99.99999%) which results in a need for rare earth metals (REMs). Once again this is typically achieved through a multi-stage solvent extraction process. Rare metals typically command even higher values than REOs. Rare earth alloys are combinations of multiple metallic elements into a single compound.
