Mining and Processing Iron: From Rock to Steel

Iron is the most commonly used metal, employed in the construction of automobiles and buildings. Five percent of the earth's crust is made of iron, but before iron can be used, it must be mined from the earth and processed. While the process of mining this most valuable of commodities is anything but simple, it has been honed and made efficient through multiple years of practice.

THE MINE
The mine itself has stepped walls each 40 feet high.
Drilling
A drill bores a series of 15-inch diameter, 55-foot deep holes into the floor of the mine, which are then packed with explosives.
Blasting
One blast each week, which frees about 1 million tons of ore.
Shoveling
Ore freed by blast is loaded by diesel-powered shovels with huge, 22- to 35-foot cubic yard shovel.

CONCENTRATING
Trucking
The trucks carry 240 tons of ore in a single load to the crusher.
Crushing
Rock smashed into 10-inch chunks and conveyed to a 450,000-ton stockpile.
Grinding
Ore goes by conveyor from the stockpile to a 36-foot diameter grinding mill. Water is added as the ore is ground into a powder.
Separating
Magnets separate the magnetite ore from waste rock. Ore becomes a liquid concentrate averaging 66 percent iron.
Tailings
Waste particles called tailings, along with water, flow by gravity to a tailing basin contained by dams. Tailings settle to the bottom of the basin and water is recycled and pumped back for use again in the plant — about 120,000 gallons per minute.

PELLETIZING
Thickening
Ore concentrate is thickened in a machine called a thickener and all but 9 percent of water removed.
Rolling
Concentrated ore is mixed with clay and limestone and sent to large rotating drums where it is rolled into small balls called “green balls.”
Making pellets
The pellets, which are easier to handle and ship, are screened and sent to a furnace where they are hardened at 2,350 degrees Fahrenheit.

TRANSPORTING
Loading
The final product, called taconite, is transported to bins and eventually loaded on trains.
Shipping
Trains transport the pellets to docks where they are loaded on ore boats and shipped to steel mills, where they are used to make steel.