36 



UNITED STATES MINERAL RESOURCES 



for military defensa Plastics, wood, and other 

 metals including copper, steel, lead, zinc, magnesium, 

 and titanium could be substituted for some of the 

 uses for aluminum. However none of these materials 

 has all the properties of aluminum, and none offers 

 much market competition for aluminum, except for 

 a few specialized uses. Both alumina (the oxide of 

 aluminum, AI2O3) and bauxite (the major ore of 

 aluminum) are used in the manufacture of refrac- 

 tories, abrasives, and chemicals. 



Bauxite is a complex impure mixture of alumi- 

 nous minerals, chiefly aluminum hydroxides. Alu- 

 mina content of most bauxites ranges from 35 to 

 50 percent; the common impurities are quartz, kao- 

 linite, and iron-oxide-bearing minerals. Bauxite 

 ores, of which there are several types, are classified 

 by mineral content, occurrence, use, and source. In 

 recent years, about 88 percent of the bauxite and 

 alumina consumed in the United States was used in 

 making metal, 4 percent in refractories, 6 percent 

 in chemical and related uses, and 2 percent in abra- 

 sives. 



Aluminum metal is made by extracting alumina 

 from bauxite by the Bayer process and by reducing 

 this oxide to metal electrolytically. In the Bayer 

 process, bauxite is leached under pressure and heat 

 by a caustic solution which converts the ore to a 

 solution of sodium aluminate and red mud waste. 

 From this solution, hydrated aluminum oxide is 

 precipitated, washed, and calcined to obtain alu- 

 mina. This alumina is then reduced to the metal by 

 electrolysis of a hot molten solution of alumina and 

 crolite, NasAlFg. Metallurgical-grade bauxite ranges 

 from 35 to 55 percent AI2O3. Depending on grade 

 and type of ore, between 4.7 and 7 short tons of 

 bauxite are required to produce 2 tons of alumina, 

 and 2 tons of this oxide are required to make 1 ton 

 of aluminum metaJ. 



Bauxite used for manufacture of abrasives, re- 

 fractories, and chemicals must meet more restrictive 

 specifications as to aluminum, silicon, iron, and 

 titanium contents than does metallurgical bauxite 

 (table 6). Although the amount of bauxite used for 

 purposes other than metal production is relatively 



Table 6. — Specifications, in percent, for abrasive, chemical, 

 and refractory grades of bauxite ' 



1 Modified from Stamper (1970, p. 440) 



= A major portion of the bauxite used by the U.S. chemical 

 exceeds 15 percent SiOz. 



small, these uses are of major importance to indus- 

 try. For example, only 2 percent of U.S. bauxite 

 consumption is used to manufacture aluminum 

 oxide abrasives ; yet this represents about half of 

 all production of artificial abrasives and more than 

 five times the total production of natural abrasives. 

 The United States is dependent mostly on imports 

 for its bauxite and alumina requirements. Exclud- 

 ing trade in alumina metal, the United States in 

 1971 produced about 2 million long dry tons of 

 bauxite, imported 13.7 million long tons of bauxite 

 and 2.3 million short tons of alumina, and exported 

 30,000 tons of bauxite, and 1.1 million tons of alu- 

 mina. In that year, the United States consumed the 

 equivalent of approximately 27 percent of the world 

 production of bauxite and produced domestically 

 only 12.5 percent of its requirements. Between 1967 

 and 1970, imports of bauxite were from Jamaica 

 (59 percent), Surinam (24 percent), and other 

 countries (17 percent). Alumina imports during the 

 same period came from Australia (52 percent), 

 Surinam (24 percent), Jamaica (18 percent), and 

 other countries (6 percent). 



UNITED STATES AND WORLD 

 BAUXITE PRODUCTION 



Aluminum was extracted from bauxite in both 

 France and England in the middle of the 19th 

 century, but less than 50 tons of metal had been 

 produced by 1885. Production increased at a rapid 

 rate in the late 1800's ; the yearly world demand for 

 bauxite, however, did not reach 1 million tons until 

 1917, during World War I. World production of 

 bauxite dropped sharply after the war and reached 

 a low of 334,000 tons in 1921. A little more than 1 

 million tons was produced in 1923, and a yearly 

 production of 2 million tons was first reached in 

 1929. World production again dropped in the de- 

 pression years of the early 1930's (fig. 7) but recov- 

 ered in the last half of the decade and reached a 

 sharp peak of more than 13 million tons in 1943. 

 Production again slumped sharply after World 

 War II as the economy changed to peacetime condi- 

 tions and accumulated stocks were consumed. After 

 recovering from this slump, world production 

 reached 11 million tons in 1951 and has since re- 

 mained on a sharply increasing trend, reaching 57 

 million tons in 1970. 



Domestic production, including the World War I 

 peak, remained below 1 million tons annually until 

 very intensive mining was started in 1942 to meet 

 World War II requirements; a record production 

 of 6.2 million tons was reached in 1943 (fig. 7). 



