42 



UNITED STATES MINERAL RESOURCES 



to many millions of tons in the Piedmont region 

 that extends from southern Virginia through the 

 western parts of South Carolina and North Carolina, 

 and northern Georgia and into northeastern Ala- 

 bama. Little is known about the composition of 

 these saprolite deposits. Analysis of a few samples 

 collected near Shelby, N.C., and Gaffney, S.C, found 

 the saprolite to contain 25-36 percent alumina, 

 partly in gibbsite but much in very fine grained 

 aluminum silicate minerals. Probably much of the 

 silica in these rocks would be reactive and deleteri- 

 ous in alumina processing. Other large saprolite 

 deposits are associated with the low-grade bauxites 

 in Hawaii, Washington, and Oregon. Saprolite also 

 occurs at several other localities in the United 

 States. 



Saprolite was investigated as a source of alumi- 

 num by several major aluminum companies during 

 the 1950's. In 1970, lai*ge acreages were leased by 

 a newly formed company to recover alumina from 

 saprolite. 



Approximately 50 million tons of ash containing 

 8-40 percent alumina is produced by burning coal 

 each year in the United States. Coal ash is an 

 unlikely present-day source of aluminum because 

 sufficient quantities are not generated in any one 

 locality, and the ash may have been heated to tem- 

 peratures that would make the alumina difficult to 

 extract. As a long-range resource, however, coal 

 ash may have some potential. If future energy re- 

 quirements necessitate the use of large amounts of 

 high-sulfur coal in steam-electric generating plants, 

 possibly alumina and sulfuric acid could be recov- 

 erable byproducts. 



COPPER-LEACH SOLUTIONS 



Recent consideration has been given to recovering 

 alumina from acid solutions used to leach copper 

 from mine dumps and low-grade copper deposits 

 in the United States (National Materials Advisory 

 Board, 1970, p. 57-60). Repeated cycling of these 

 solutions increases the alumina content; one copper 

 company estimated that the amount of leach solu- 

 tion it circulated daily contains 1,000 tons of alu- 

 mina. Potential resources of as much as 2,000 tons 

 of alumina per day are estimated to be available 

 from operations of 14 copper mines in the United 

 States. 



PROBLEMS FOR RESEARCH 



On the assumption of a politically stable period 

 in the world, it seems likely that the growing de- 



mand in the future for aluminum in the United 

 States will be met largely by imports. It is antici- 

 pated that the current trend of increasing imports 

 of alumina and aluminum, rather than of bauxite, 

 will continue. This condition could change if meth- 

 ods are developed for economic recovery of alumi- 

 num and coproducts from nonbauxite domestic 

 sources. High-alumina clay, dawsonite-bearing oil 

 shale, and possibly alunite seem to be the most 

 promising nonbauxite domestic sources of alumi- 

 num. 



Continued research on the geology of bauxite de- 

 posits of the world is needed. This research should 

 include exploration for additional major deposits, 

 particularly in tropical areas, as well as continued 

 investigations of the size, depth, thickness, grade, 

 composition, impurities, and possible byproducts of 

 known foreign deposits. 



New tools and methods to aid in prospecting and 

 in the evaluation of bauxite deposits would indeed 

 be useful. In the past, in the evaluation of deposits 

 no substitute has been found for detailed angering 

 or drilling and the analyzing of numerous samples. 

 A breakthrough in expediting the analytical work- 

 load may have come recently when one company 

 introduced a modern semimobile laboratory in the 

 Amazon Basin bauxite region (Mining Engineer- 

 ing, 1971). This laboratory is reported to have an 

 atomic-absorption spectrophotometer, photoelectric 

 colorimeter, and a rotating heat-pressure digestion 

 system. Another major aid in exploration may re- 

 sult from a neutron-activation probe developed by 

 Allan B. Tanner, Robert M. Moxham, and Frank E. 

 Senftle of the U.S. Geological Survey and J. A. 

 Baicker of the Princeton Gamma Tech Corporation 

 (Tanner and others, 1972). This probe, when low- 

 ered down a drill hole, will provide semiquantitative 

 determinations of the aluminum in the wallrock. In- 

 formation on the content of titanium, iron, and 

 other possible metallic byproducts in the bauxite 

 might also be obtained by this method. 



Additional research and information are needed 

 on domestic potential sources of aluminum and on 

 the location, size, grade, and principal mineral and 

 impurity contents in several high-alumina clay de- 

 posits. Detailed studies of the geology, mining, and 

 metallurgy of the dawsonite-bearing oil-shale de- 

 posits in Colorado by the U.S. Geological Survey 

 and the U.S. Bureau of Mines are continuing. If the 

 reported large deposit of alunite in Utah is con- 

 firmed, geologic studies of this deposit and similar 

 ones in the Western United States would be war- 

 ranted. Much information related to costs of ex- 

 tracting alumina from non-bauxite materials is also 



