292 



UNITED STATES MINERAL RESOURCES 



Lake Superior region, in low-grade ores that require bene- 

 ficiation and agglomeration to make them usable. 



Research is needed to appraise the economic potential of 

 domestic iron-ore deposits, to develop better techniques for 

 utilizing low-grade ores, and to minimize environmental 

 problems resulting from mining and processing the ores. 



INTRODUCTION 



Iron is the principal metal employed in modern 

 industrial civilization. It is an abundant and readily 

 extractable gray metal that has a favorable com- 

 bination of physical characteristics such as hard- 

 ness, strength, and durability combined with prop- 

 erties that make possible its fabrication into a 

 myriad of useful forms. Alloying of iron and other 

 elements to form steels, in which one or more of 

 the desirable properties of iron are greatly en- 

 hanced, has greatly extended the usefulness of the 

 metal. In addition to its many applications in metal- 

 lic form as steel, iron is combined chemically with 

 many other elements to produce many useful com- 

 pounds. 



The history of man in terms of use of materials 

 has progressed from the stone age through the 

 bronze age through the iron age, and even though 

 the present period is sometimes referred to as the 

 atomic age, iron in the form of steel still is a basic 

 necessity in the technological fabric of nations. 



The industrially developed nations of the world 

 could not maintain their present high standards of 

 living without the continued production and use of 

 large quantities of iron and steel products. Nations 

 are ranked in industrial development partly on the 

 basis of total production and per capita consumption 

 of steel. The higher levels in standard of living 

 toward which the peoples of developing nations 

 strive involve ever-increasing use of steel. 



Iron and steel have become indispensable in our 

 everyday living. They are used in structural compo- 

 nents, transportation equipment, tools, containers, 

 fasteners, pigments, and many other materials. A 

 measure of the sustained use of steel in our economy 

 is indicated by the records of steel production in 

 the United States during the past two decades as 

 shown in figure 33. 



This graph tells only part of the story, for it does 

 not indicate steel imports. Large cumulative quan- 

 tities of iron and steel products are being used in 

 the form of durable items such as bridges, building 

 frames, pipelines, railroads, wire, and countless 

 other items that perform their functions for decades 

 or longer. 



Although other materials, such as wood, alumi- 

 num, and plastics, are and may continue to be used 

 as substitutes for steel in some items of manufac- 



X 115 



1955 



1959 



1967 



1971 



Figure 33. — Steel production in the United States, 1951-71. 

 Data from U.S. Bureau of Mines Minerals Yearbooks 

 (1951-70) and Commodity Data Summaries (1972). 



ture, there are no practical substitutes for iron and 

 iron alloys — steel — for a broad spectrum of pur- 

 poses. The development of special varieties of steel, 

 however, has reduced the amount of steel needed 

 for many purposes. Stronger steel for structural 

 purposes, such as in building frames and bridges, 

 provides equal or greater strength with less material 

 than ordinary steel, and corrosion-resistant steels 

 used in place of ordinary steels have extended the 

 period of usefulness of other items. The recycling 

 of scrap metal has also reduced the amount of pri- 

 mary metal required to meet demand. Consumption 

 of iron and steel scrap in the United States in 1971 

 was estimated to be more than 80 million short tons 

 (U.S. Bur. Mines, 1972). 



World production of iron ore has trebled during 

 the past two decades, rising from 250 million long 

 tons in 1950 to approximately 750 million tons in 

 1971, as shown in figure 34. Also shown in figure 

 34 is world trade in iron ore, which has more than 

 doubled since 1955. During the same period annual 

 domestic production of iron ore in the United States 

 has fluctuated between about 60 million tons and 



