Our ore bodies were formed during the Midcontinent Rift tectonic event 1.1 billion years ago. This rifting, or breaking apart, separating, and thinning of the Earth’s crust allowed magma deep within the Earth to rise up through the crust and cool as igneous bodies.
Our ore deposits were the result of at least three different intrusions of magma rich in metals. As the magma cooled, nickel and copper minerals crystallized into a solid ore body. The bottom of the ore body sits roughly 3,000 feet deep and measures to be roughly 6 acres in size.
We have two ore types; massive and semi-massive sulfide. Massive sulfide is about 6.5 percent nickel and 3.8 percent copper. Semi-massive contains about 1.5-3% nickel and copper. The Eagle deposit is high-grade nickel and copper, but also contains trace amounts of cobalt, platinum, palladium, silver, and gold.
PRODUCING NICKEL & COPPER
THE MINING JOURNEY
Eagle Mine in Michigan's Upper Peninsula will produce approximately 440 million pounds of nickel and 429 million pounds of copper. In fact, now in production, Eagle Mine is the only primary nickel mine in the United States and produces 1.5 percent of the world's nickel.
So how do we get our ore out from 3,000 feet below the surface?
First, we make a tunnel underground that's one mile long, declining at a 13% grade and 18 feet in diameter. This tunnel serves as our main route for trucks, equipment, and miners to get safely in and around the mine.
The mining process is done in three stages. First, holes are drilled and loaded with explosives that are set off, and the ore breaks apart. Second, the loosened ore is now mucked or scooped and put into special underground haul trucks. Each truck delivers roughly 100,000 pounds of ore to the surface. We extract our ore with Long Hole Stope and Cut and Fill mining techniques. Third, we mine from the bottom up, and once an area is mined, we fill it with a special mix of rock and concrete. This helps the ground stay nice and solid so we can continue to mine the other areas.
Drill holes are filled with explosives. At the end of each mining shift, blasts are set off from the surface.
Once the ore has fallen from the blast,
an underground truck will scoop and dump the ore into a haul truck that will bring it to the surface.
Low profile underground haul trucks are filled with a mix of rock, aggregate, and concrete from the Backfill Plant before heading back underground. Backfilling provides ground and wall support so adjacent stopes can be mined.
Next up, semi-trucks get loaded with the rock and drive over 60 miles to the Humboldt Mill using the same roads we use every day to go to school, work, and the store.
Approximately 44 round trips are made per day between the mine and mill sites with each load weighing on average between 40-45 metric tons.
Safety is stressed with our ore truck drivers, which is why we constantly monitor speed, location, and braking efforts throughout the entire transportation process.
Our transport plan uses existing roads for ore transportation; including AAA, CR510, CR550, Sugarloaf Avenue, Wright Street, US41, M-95, and CR601. Haul trucks adhere to all Michigan Department of Transportation guidelines, including those for length and weight.
Ore is stored in the Coarse Ore Storage Building on the mine surface. Inside the COSA, a front-end loader fills road haul trucks with ore on average 18-24 inches in size.
Truckloads are covered before passing through the truck wash and continuing off-site to travel approximately 60 miles to the Humboldt Mill.
TRUCKS HEAD TO MILL
Our trucks make their journey to the mill, where they drop off the ore before it goes through our milling process.
Conventional crushing, grinding, flotation, and pressing are used to process run-of-mine ore into separate nickel and copper concentrates. Road haul trucks arrive at the mill and dump their load in the enclosed Coarse Ore Storage Area. Each truckload weighs on average between 40-45 tonnes.
Ore will go through three stages of crushing before the grinding circuit pulverizes the ore to 80 microns (a texture similar to fine sand). Water is introduced and a series of flotation separates the nickel from the copper. We work to remove as much water as we can by thickening and pressing the mixture.
Rail cars are then filled by a front-end loader, covered, and sent to our customers. Nickel and copper concentrates will then have to go through smelting and refining before becoming 99.9 percent nickel and copper.
The material left over once the nickel and copper have been extracted is referred to as tailings. The tailings are sent to the Humboldt Tailings Disposal Facility (HTDF) where they are stored underwater. Water from the HTDF is decanted off the top and pumped back to the mill as process water. Excess water is treated at the on-site water treatment plant before being recycled to the environment.
Once the ore from the the mine arrives to the mill, it is stockpiled in the Coarse Ore Storage Area. Oversized material is broken with a rock hammer until it is small enough to be sent to the primary crusher.
Three stages of crushing reduce the size of the ore from 18 inches, to 4 inches, and finally to less than ½ inch.
Grinding is conducted in two ball mills where 3 inch chrome balls reduce the ore from less than ½ inch to 80 microns, creating a texture similar to fine sand. Water is added to the pulverized ore to create a slurry.
The slurry begins a process called froth flotation. When air bubbles are introduced to the slurry, the minerals attach to the bubbles and float to the surface, where they are skimmed off. Both the nickel and copper float off together, and then the nickel is separated from the copper. The results of this are two distinct products: a nickel concentrate and a copper concentrate. The last step in the process is to thicken the slurry and remove the excess water.
The concentrates are loaded into covered
rail cars and shipped to customers for further refinement. The final product will be 99.9% pure nickel and copper used to manufacture everyday items such as cell phones and automobiles.
The material left over once the nickel and copper have been extracted is referred to as tailings. The tailings are sent to the Humboldt Tailings Disposal Facility (HTDF) where they are stored under water. Water from the HTDF is decanted off the top and pumped back to the mill as process water. Excess water is treated at the on-site water treatment plant before being recycled to the environment.
THE PRODUCTS WE PRODUCE
From medical equipment to transportation, nickel is found in many of the products that make modern life possible. Manufacturers often prefer to use nickel alloys over other materials because they are more resistant to corrosion, tolerant of high and low temperatures, strong and contain magnetic and electronic properties. At the end of their useful life, about 25 to 35 years, nickel products are easily recycled for future use. In fact, about half of the nickel in modern stainless steel products comes from recycled sources. Eagle will produce 440 million pounds of nickel.
Today copper can be found in many of the products that we use every day including home appliances, vehicle parts, and electrical components. Copper can easily be shaped, molded, rolled into sheets, or drawn into thin wire. It does not easily rust and is an excellent conductor of electricity and heat. In many respects, modern life would not be possible without copper. Eagle will produce 429 million pounds of copper.
While minor to our overall business, our processes recover Cobalt, Platinum, Palladium, Silver, and Gold within the copper and nickel concentrate and are further recovered and refined at the smelter.