This page describes some details of the mining process.

Once the ore is loaded on to the haul trucks the trucks bring it to the "pocket", an elevated platform that has a conveyor at the bottom to bring the ore to the crusher and other places in the plant. The trucks also carry overburden of course and that load is put into a different pile to be used later in mine recovery operations or to be used as fill.

The conveyor belts take the ore from the truck pockets and put it in stock piles. Forming the piles allows the maximum operation of both the trucks and the crushing and enriching equipment. The ore is crushed into a very fine power were magnets pick up the magnetic iron containing ore called magnetite. An old magnet still covered with magnetite is in the photo at the lower right. Notice the fine hair like projections that are a result of the magnetic particles following the field lines of the magnet.

Crushers use either steel balls or other rocks to break the big rocks into smaller ones. The fine material is then fed into rotating drums where the magnets pick up the magnetic ore and send it off for washing and binding with bentonite clay.

The process of ore enrichment starts with the magnetite (often called taconite) containing 20-30% iron being crushed to a fine powder.  The magnetic iron is separated from the other slate and chert by magnets.  The "good" part is called iron concentrate and contains more than 60% iron.  The rest of the material is known as tailings.  The iron concentrate is mixed with a bentonite clay binder from the Black Hills of SD, rolled into marble sized pellets.  The pellets are baked in a furnace or kiln at 2,400 °F in order to harden them for shipping. The baking process also causes them to lose the magnetic properties. It is the uniform size and lack of silica (quartz or sand) that makes it efficient for the blast furnace that turns it into molten iron and then steel. While hematite ore has an iron content as large or sometimes larger than these pellets it also is not uniform in size and often contains large amounts of silica. The non uniform size makes it difficult to mechanically control the smelting process and the silica causes glass to form in the furnace that must then be mechanically chipped off. Because of these problems very little natural ore is used in today's steel mills. The photo at the right is of a haul truck that is being repaired. Notice the mechanic next to the wheel to give a sense of size.  Below is a separation drum that is undergoing maintenance. The size of the machinery is necessary to get the productivity necessary for the companies to make a profit. The margin between making money and not is very thin with such large investments in equipment. It is important to schedule maintenance and repairs to minimize down time and keep productivity as high as possible. The process is much different than the early days of underground mining with pick axes, shovels and mule carts (in the bottom two photos).

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