The science of extracting metals has changed significantly over the years due to advancements in new technologies. The Twin Metals Minnesota project will be an underground mine, limiting surface impacts, and will utilize state-of-the-art modern mining technologies and industry best-practices.
In an underground mine, extracting strategic metals involves several steps prior to creating usable end products:
MINING: The process begins with the mineral-bearing ore (material with positive economic value) extracted from at least hundreds of feet beneath the surface. In reaching the ore, developmental rock is also extracted and used for barricading areas or to fill voids underground. The Twin Metals Minnesota project will process approximately 20,000 tons of mineralized ore per day.
CRUSHING AND GRINDING: Once the ore is retrieved, it is crushed in several stages and eventually ground into a fine sand-like consistency, liberating and exposing the surfaces of the contained mineral particles.
METALLURGY: The ground ore is processed through several stages of metallurgical extraction and separation. The exact metallurgical process Twin Metals Minnesota will use is still being examined as part of the project’s engineering studies. One of the processes that will be used is called “flotation”.
FLOTATION: The finely ground mineral-bearing material is mixed with a specialized water-chemical-air solution, where the desired mineral particles attach to air bubbles, float to the surface and are skimmed off for further processing. The recovered mineral mix is called a “concentrate” and in the form of a “slurry.”
TAILING: The non-mineral particles not captured in flotation – known as tailing – are sent to treatment facilities. Water is extracted from the tailing and then reused in mineral processing. For the Twin Metals Minnesota project, about half of the sand-like tailing material will be stored as permanent, cemented backfill providing structural support for the underground mine, with the other half stored in a modern, lined surface storage facility. Testing shows that tailings from the Twin Metals Project will be non-acid generating.
END PRODUCT: The recovered minerals are manufactured into metals, such as copper and nickel “cathodes,” which are measured in tons; or bulk precious metals such as platinum, palladium and gold, measured in ounces. The metals are then sold to customers around the world to incorporate into end user products, such as copper wire for houses, steel or batteries.