Guest Column by GeoT
We live in several "ages" at the moment the Space Age, the Nuclear Age, even the Age of Cyberspace -- but there is one age that began thousands of years ago that remains with us and that is the Iron Age.
Even in the 21st century there is no practical way for us to live without products made of iron and its close relative steel. Oh, aluminum has made major advances in product use but iron is by far the mainstay for many things. Engine blocks, structural steel, steel for rail equipment, ships, barges, bridges, car bodies and appliances even the case of my computer tower is made of steel! One auto manufacturer is touting the safety of one its steel bodied cars over that of a fiberglass roadster.
The Iron Age is believed to have begun between 1900 to 1400 BCE in western Asia. People began smelting iron to make the items they desired at first, mostly ornaments and ceremonial weapons. The oldest known artifact of hammered iron is a dagger found in Egypt, it is dated at approximately 1350 BCE. Its origin is believed to be what is now Syria or southeastern Turkey the Hittite world. Items made of iron were much stronger than those made of copper and bronze though those metals had their "ages" too. With the fall of the Hittites, the knowledge of iron working spread to other areas, including Europe.
Iron makes up 5% of the earths crust, but massive deposits of economic value are another story. The browns and reds so common in rocks and soils are usually due to the presence of iron but too minor in content to be of value.
So, where did all this iron come from, and where are important deposits found today?
Among the worlds best known deposits of iron is the Mesabi Range of northeastern Minnesota. "Mesabi" is an Ojibwa name meaning "giant." It's a giant area of low rolling hills. This deposit was discovered by Leonidas Merritt and his brothers in 1887 and mining began in 1892.
Other iron ranges lie nearby the Vermilion to the northeast, the Cuyuna to the south, the Gogebic, Marquette, and Menoninee Ranges in the upper peninsula of Michigan. These are 'banded' (stratified) iron and silica formations of Precambrian age the only time such iron formations were created. Exactly what was going on at that time is a matter of speculation but this much we know: the several massive deposits of iron found on earth were formed during this Precambrian time period. They also contain some of the earliest known fossils Stromatolites some of them likely to be of algal origin. The interbedded deposits of iron, chert, siliceous shale, slate, and carbonate rocks date from the Cryptozoic time of the Pre-Cambrian, some 1700 to 3000 million years BP (before present). No banded iron formations are known in younger rock masses. One theory states that at this early time, the atmosphere of earth was deficient in oxygen, and the iron and silica weathered from existing rock was transported to ocean basins with no oxidation. Here, they were precipitated directly or indirectly by biologic processes to form the silica-rich iron deposits. Liberation of oxygen by the ancient algae possibly played an important role in all of this. No one knows but it's interesting to think about.
Heavy precipitation and subsequent weathering of iron in localized areas resulted in zones of high grade ore Hematite, Fe2O3 - up to 70% iron. Such was the heart of the Mesabi Range. Miners, kind of like kids who eat what they like first used this rich and easily accessible ore early on in the range's development. This is the ore that had a great deal to do with building the infrastructure of the United States during its booming years of growth. Tremendous amounts of less desirable Taconite ore remained unexploited we'll return to that subject later.
The Mesabi Range is a belt of iron ore 110 miles long, averaging 1 to 3 miles wide, and reaching a thickness as great as 500 feet. It is located between Grand Rapids and Babbit, Minnesota. Much of the ore is close enough to the surface to be mined by the "Open Pit" method but not all, there were underground mines too.
Finding this resource was an important event in 1887 but the need for the iron was not in northeastern Minnesota it was in the northeastern United States. Here is where economics and geography intermingle. The ore was so rich it was more profitable to ship the iron to the eastern coal for smelting, than to ship coal to the iron. Besides, the markets for iron and steel were in the rapidly expanding eastern U.S., not Minnesota.
Now, the next problem was how to ship the ore. The Great Lakes provided a natural transportation system but with a problem: the difference in elevation between Lake Superior and Lake Huron. At Sault Saint Marie and, more specifically at Saint Marys Falls, the Saint Marys River tumbles 21 feet from Lake Superior and Lake Huron. Canals with a lock had been constructed to connect the lakes as early as 1797 for fur trading and general small-scale transportation purposes but now a much larger and longer lock system would be needed to handle the ships being built to carry the ore. This was accomplished at the Soo Locks and this canal is among the busiest in the world. (It does freeze and is closed to navigation in the winter months).
A great deal of mining took place through the years and eventually the high-grade ore body was consumed. This happened in the 1950's. World War II had taken a heavy toll on that rich body of ore. But, there was still that lesser ore called Taconite. There was a good reason why it had never been used!
The problem was: Taconite is a low-grade ore containing only up to 30% Magnetite and Hematite. These tiny particles are scattered throughout a very tough variety of quartz called chert, and, early on, this ore was not of economic value, and was technologically impossible to use. But, necessity being the mother of invention, ways were found to use a flame-throwing rock drill to bore into the hard formations for blasting, and to economically crush and then separate the iron from the rock. A way had to be found to concentrate the pulverized ore for shipment. They did. The result are called taconite pellets -- about the size of marbles. The iron powder is moistened, combined with Bentonite clay as a binder, limestone and dolomite as a flux, rolled into 3/8 of an inch spheres, and then fired into the hard round pellets suitable for use in a blast furnace. They contain up to 65% pure iron and they are magnetic to boot! (No shipping in aluminum railcars though an electrolytic reaction occurs between the two metals!) The process is called Beneficiation and was developed at the University of Minnesota over a period of many years. Dr. E.W. Davis led the research and experimentation. He knew the wealth Taconite contained, and found the way to get it out. This was very good news for the Mesabi Range.
The pellets are railed to Lake Superior ports, and then on to midwestern and eastern steel mills aboard the Great Lakes carriers. Taconite pellets from Minnesota have also been shipped by rail to steel mills as far away as Alabama and Utah! Escapees can be found along the CSX rails in eastern Illinois.
Today the Mesabi Range of Minnesota finds itself very much alive and well producing 75% of all domestic ore - but, as always, subject to the whims and fancies of the iron and steel consuming economy. And, of course, imports -- not only of iron ore, but also finished steel from offshore locations.
So, as Tonto might have said to the Lone Ranger "Now we know more about the Mesabi...Kemosabi!"
GeoT is a long-time high school geography teacher from Illinois. In addition to geography, he enjoys railroads and model railroads, old Oldsmobiles, and gardening.