Jeff Kubel, age 12, of Cudahy, Wis., for his question:
WHAT IS TACONITE?
Iron is one of the most useful building materials known to man. Every day we come into contact with hundreds of products made from it from nails to razor blades to toys. And many other vital products are made on machines made of iron and iron alloys. The source of iron is Mother Earth, and taconite is just one of the ores, that yield this indispensable metal.
The iron that we use for so many things is found in the earth. Generally it is hidden in some mineral or combined with other chemicals. A mineral that contains a metal we want is called an ore, and the principal ores from which iron is produced are hematite, limonite, magnetite and taconite.
Geologists know that taconite ore is about 30 percent iron oxide. But it is also a very hard rock so hard, in fact, that regular drilling and blasting methods hardly faze it. The iron content, however, was so desirable that in the early 1950s mining engineers went to work to see if they could crack the stubborn stuff. In time the problem was solved, for even the rough taconite could not resist the new mining methods.
Even hard rocks tend to crack under such forces as heat and pressure, or sudden temperature .changes. The methods for cracking taconite, making good use of this information, employed intense heat followed by a shower of gushing cold water. The heat is supplied by a machine that shoots out streams of burning kerosene. The temperature of the taconite soars upwards to about 4,700 degrees F., making it white hot. A shower of cold water produces great clouds of steam, and the sudden change in temperature causes the stubborn mineral to crack.
This is just enough of an opening for the next mining operation.
Explosive charges are placed in the cracks and detonated. The explosions blast the hard rock apart in huge chunks. The next order of business is to grind it up into smaller and smaller bits. After several different grinders have reduced the ore to a fine powder, mighty magnets separate the useful taconite from sand and other rocky waste materials.
Coal dust is now added to the powdered taconite and fed into a steel barrel and heated. In the process, the coal dust is burned away and the taconite forms into small round marbles. These marbles are ready to be shipped to steel mills where they will be mixed with other materials to produce steel or iron.
Taconite iron ore was named for deposits found in the Taconic Mountains of western Massachusetts and Vermont. Later, massive deposits were located in Minnesota along the Mesabi Range. The first successful taconite mine was started at Silver Bay, Minn., in 1955. Credit for developing the mining process of taconite is given to Edward Davis.