ALUMINUM AND BAUXITE 



41 



localities of minor importance. Possibly, oil-shale 

 deposits of lacustrine origin elsewhere in the world 

 have potential for content of dawsonite and other 

 sodium carbonate minerals. 



HIGH-ALUMINA CLAYS 



High-alumina clays consisting mainly of kaolinite 

 have long been considered as a possible source of 

 aluminum. During the World War II emergency, the 

 possibilities for extracting alumina from such clays 

 were evaluated in pilot plants at Salem, Ore., and 

 Harleyville, S. C. Clays of this type were used as a 

 source of aluminum in Germany and Japan during 

 that war and have been investigated as a source of 

 aluminum in Poland, the U.S.S.R., South Africa, and 

 elsewhere in recent years. High-alumina clays have 

 long been considered by the U.S. Geological Survey 

 and the U.S. Bureau of Mines to be the most favor- 

 able potential source of aluminum from nonbauxite 

 rocks in the United States, because of their high 

 aluminum content and their availability. A panel 

 of academic and industrial experts in liaison with 

 government officials recently reaffirmed this posi- 

 tion (National Materials Advisory Board, 1970, 

 p. 1). 



High-alumina kaolin and kaolinitic and refractory 

 clays having alumina contents of 25-35 percent 

 occur at many places in the United States (Patter- 

 son, 1967, p. 129-145 ; U.S. Bureau of Mines, 1967 ; 

 chapter on "Clays"), mainly in sedimentary rocks 

 of Pennsylvanian, Cretaceous, and Tertiary ages. 

 Though the total resource of clays containing as 

 much as 25 percent alumina is extremely large, the 

 deposits that realistically can be considered to be 

 major potential sources of aluminum are more lim- 

 ited. Those clays which are likely to be used for 

 aluminum, if a breakthrough of the use of such 

 materials is ever achieved, are likely to have rather 

 restrictive characteristics ; most particularly they 

 will be high in grade, having average alumina con- 

 tents of approximately 35 percent; and they will 

 occur in very large deposits under geologic condi- 

 tions permitting cheap strip mining and will be on 

 lands owned by aluminum companies or on lands 

 that can be acquired at a comparatively low cost. 

 The principal limitation on the availability of high- 

 alumina clay is that most of the large high-grade 

 deposits under light overburden are now owned by 

 companies producing various grades of kaolin and 

 refractory and ceramic clays, and the value of these 

 deposits for these uses is greater than for recovery 

 of aluminum. 



Areas where high-grade clay in quantities of 50 

 million tons are likely to be available include (1) 



deposits associated with bauxite in Arkansas; (2) 

 the extensive Georgia kaolin belt; and (3) a belt of 

 Eocene clay including the Andersonville district, 

 Georgia, and extending northeast and southwest 

 from that belt. The total amount of high-alumina 

 clay in the United States containing 25 percent 

 AI2O3 or more and under no limits of availability, 

 overburden, or mining costs may be as much as 10 

 billion tons. 



IGNEOUS ROCKS 



Nepheline syenite and anorthosite are two igneous 

 rocks that are potential sources of aluminum. 

 Nepheline syenite is a medium- to coarse-grained 

 soda-rich rock composed chiefly of nepheline, alkalic 

 feldspars, and ferromagnesian minerals. In Arkan- 

 sas, the alumina content of nepheline syenite ranges 

 from 18 to 20 percent. Deposits of nepheline syenite 

 occur in many other places in the United States and 

 elsewhere in the world. A deposit of nepheline 

 syenite in the Kola Peninsula, U.S.S.R., containing 

 considerably more alumina than the Arkansas rock, 

 has produced metal-grade alumina, fertilizer, fluor- 

 ine, and cement for several years. A large new plant 

 using similar rock in southern Siberia is also re- 

 ported to be in production. 



Anorthosite, a medium- to coarse-grained igneous 

 rock, is composed mostly of plagioclase feldspar and 

 contains 23-28 percent alumina. The rock forms 

 large intrusive masses of Precambrian age near 

 Laramie, Wyo., in California, in New York, and in 

 many other localities in the United States and else- 

 where in the world. A pilot plant operated in the 

 early 1950's by the U.S. Bureau of Mines tested a 

 method of recovering metal-grade alumina and 

 cement from Wyoming. This work proved alumina 

 can be recovered from the rock, but not at currently 

 competitive costs. In the summer of 1972, the Alu- 

 minum Company of America announced the pur- 

 chase of a large deposit of anorthosite in Wyoming. 



Neither nepheline syenite nor anorthosite is likely 

 to become a source of aluminum in the United States 

 in the near future, although both constitute enor- 

 mous low-grade resources amounting to billions of 

 tons. 



SAPROLITE 



Saprolite is a rock whose original minerals are 

 replaced by others during weathering but whose 

 original textures and structures are preserved. The 

 physical and chemical characteristics of these rocks 

 are dependent on climate and drainage as well as 

 the composition of the parent material. In the United 

 States, saprolite deposits are extensive, amounting 



