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The Rouchleau mine pit is a the center of the "Virginia
Horn", an easily recognizable feature of geologic maps in Minnesota. On this linked map,
the Biwabik Iron Formation is colored red. Near the center of the red
"stripe" is a z shaped squiggle (the center of the map at left and
lower left) that is
called the Virginia Horn. The
Rouchleau mine pit is a natural ore mine going almost north-south in
the middle of the horn. The overlook is just off Highways 169 and
53. Natural ore (or direct ore) was the first ore mined from the Mesabi Iron Range. The ore made up of hematite and goethite was easily dug out of the ground due to the soft and weathered nature of the rocks.1 The natural ores were formed by oxidation of iron containing minerals by circulating water. Two different ideas on the source of the water include the idea of underground water sources coming up to the surface and rain water sources percolating downward. Major concentrations of natural ore are often found near earth quake fault lines. This is the case for the Rouchleau Mine. The Rouchleau Mine and some smaller adjacent mines occupy a distance of over 3 miles along a fault and the Biwabik Iron Formation is over 500 feet thick (note the evergreen trees that are about 30 feet tall) at this point. The hills in the horizon (to the north in the photo) are part of the Giant's Range (next page). |
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| The mining process is a large
industrialized operation. At the Rouchleau Pit Overlook there is a
scale model of one mining operation (Minntac) with educational
descriptions. Just outside the door of the center are some samples of
the "smaller" haul trucks that are used in the mines. The natural ores
being mostly depleted and the advantage of using processed uniform ore
pellets have resulted in large scale enrichment processing or magnetic
(taconite) iron ore. |
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Looking to the west is Highways 169 & 53 and past that
the "dumps" from other mining operations. Further north at the horizon
you can see and hear the mining operation at Mountain Iron. The plant
is owned by United States Steel Corporation (the plant is called
Minntac). At Minntac the ore is from the lower part of the Biwabik Iron
Formation, often called taconite, and not the natural ores mined
earlier in the 1900's. This mine and others in northern Minnesota are in danger of closing in part because of the shipping costs and costs of updating equipment. Iron mines in eastern South America can ship ore to eastern US steel mills cheaper than the rail train shipment from here to Lake Superior. As the mining equipment, especially the crushers and kilns, need updating it is more economical for the steel mills to buy the ore from South America than it is to continue mining |
1.
Minnesota Minerals Education Workshop, August, 2003
