Sidney Alderson, age 11, of New Bedford, Mass., for his question:
HOW IS TACONITE PROCESSED?
Taconite is a hard rock that contains about 30 percent iron in the form of fine specks of iron oxide. The rock is extremely hard. Processing taconite involves several very complicated steps.
First the rock is so hard that ordinary drilling and blasting methods cannot be used. Instead, miners have to use a jet piercing machine, which shoots alternate streams of burning kerosene and cold water.
The kerosene heats the taconite to about 4700 degrees Fahrenheit, making it white hot. The cold water jet then cracks the rock by suddenly changing its temperature. Engineers can than blast the taconite into chunks.
Next the taconite goes through several stages of crushing, until the pieces are less than three quarters of an inch in size. Large cylinders then grind it down into even smaller pieces and magnets separate the usful taconite from waste sand.
After the taconite has been ground almost to a powder and purified, it is fed into a steel barrel. The particles of taconite, when mixed with coal dust and heated, form marble sized balls. When the coal burns away, the taconite marbles are strong enough to stand up well in shipment to the blast furnaces where they are used to make iron.
Taconite is named for the Taconic Mountains of western Massachusetts and Vermont.
Taconite is found in large quantities in the Mesabi Range of Minnesota. It is the mother rock from which the great Mesabi iron ore deposits were formed. These import iron ore deposits lie like raisins in a great cake of taconite, 100 miles long and one to two miles wide.
The iron in taconite occurs principally as the black oxide magnetite, or loadstone, and the red oxide hematite.
The first large scale taconite processing plant was opened in 1955 by Reserve Mining Company in Silver Bay, Minn. Orders were issued by a federal court in 1975 to develop a plan to end water pollution in Lake Superior and also to reduce air pollution caused by the plant's method of discharging taconite waste materials.
A mining engineer named Edward Wilson Davis is known as the father of taconite because he discovered how to get iron ore from taconite rocks. Davis was born in Cambridge City, Ind., in 1888. For many years he taught mining engineering at the University of Minnesota.
Taconite rock was successfully treated to remove iron by Davis at the University of Minnesota in 1943.
Iron ore which contains relatively small amounts of iron is called lean, wash, low grade, intermediate, taconite or concentrating ore