National Geographic : 1949 Sep
If Misery Loves Company, This Should Be Ideal-150 Dentist Chairs in One Big Room Actually, there's a minimum of pain, for the most up-to-date methods are used at this huge clinic of the University of Minnesota's School of Dentistry at Minneapolis (page 315). Under supervision of well-qualified dentists, juniors and seniors gain practical experience here. Patients pay only the cost of materials. or tossed aside in mining rich magnetite and hematite. Here is an experiment in which every American has a financial stake. Every time you pick up a needle, open a "tin" can, fire a gun, or drive a car, more likely than not you are using Minnesota iron. Seventy percent of the iron used in the country comes from here.* Iron ore even richer than Nature's product can be made from taconite, a rock which is 20 to 35 percent iron and so abundant here it would meet the Nation's needs for centuries. At the University of Minnesota's Mines Ex periment Station, long-visioned, persistent Dr. E. W. Davis last year made the first pig iron from Minnesota taconite. There he showed me how iron from the magnetic form of the rock is concentrated. Broken and pulverized, the taconite is passed under magnets which pull out the tiny dark bits of iron. When packed into pellets like black marbles, this concentrate is ready for the blast furnaces. Its iron content is about 65 percent compared to 50 to 55 percent for the nature-made open pit ore. Up in the iron country private industry is trying this and other ways of getting iron from rock. Machine Parts from Powdered Iron Even more interesting is the attack on the carbonate slate, 24 percent iron. Bya chemical method developed by the late C. V. Firth at the University of Minnesota, this abundant rock can be made to yield powdered iron of 98 or 99 percent purity. Near Aurora, where the red-pitted Mesabi Range meets the vast northern wilderness area, a plant was erected last year with the funds and cooperation of the State to turn * See "Steel: Master of Them All," by Albert W. Atwood, NATIONAL GEOGRAPHIC MAGAZINE, April, 1947.