374 



UNITED STATES MINERAL RESOURCES 



percent recoverable lepidolite, and about 200,000 tons 

 of crude petalite ores of somewhat higher yield." 

 These figures suggest a total of about 4,000 tons of 

 lithium. 



No published data appear to be available to calcu- 

 late resources in the Manono deposits. Republic of 

 the Congo, though the quantity seems to be immense 

 (Kesler, 1960, p. 527). Eilertsen (1965, p. 534) men- 

 tioned deposits in the Republic of Mali that have 

 8,000 tons of lithium. In several other African coun- 

 tries lithium minerals have been mined or the exist- 

 ence of lithium pegmatites has been noted. The hypo- 

 thetical resources of Africa may be estimated at 

 1 million tons of lithium. 



EURASIA, AUSTRALIA, AND SOUTH AMERICA 



Noakes (1946) recorded resources amounting to 

 1,000 tons of lithium in western Australia, and 

 Eilertsen (1965, p. 534) mentioned 4,000 tons in 

 the same region. Lithium pegmatites in South 

 America and Eurasia, though numerous and wide- 

 spread, seem not to be large, or at least no pub- 

 lished statement to the contrary has been noticed. 

 The U.S.S.R. has at least a few deposits and has 

 recently exported lithium compounds (Luckenbach, 

 1970, p. 83), though not in sufficient abundance to 

 suggest that the country has any truly large mine. 



The identified resources throughout the vast re- 

 gions of Eurasia, South America, and Australia 

 seem too small to take into account in this report, 

 and there are no grounds at all for estimating 

 hypothetical resources. This is not to say, however, 

 that sizable resources will not ultimately be dis- 

 covered. 



RESOURCES IN BRINES 



The key to any estimate of the overall lithium 

 resources in brines is the Silver Peak deposit, 

 Nevada, for which the Foote Mineral Co. reported 

 reserves of 5-10 billion pounds of lithium (Foote 

 Mineral Co., 1967, p. 24; Luckenbach, 1968). De- 

 tails of how these reserve figures were computed 

 have not been published, but enough numerical data 

 are available so that with only a few assumptions 

 the calculations can be approximately duplicated. 

 Barrett and O'Neill (1970, p. 47) provided figures of 

 32 square miles for the area of the playa, 600 feet 

 for the minimum thickness of the brine-bearing 

 body, and 300 ppm for the content of lithium in the 

 brine. Using these data and guessing that the brine 

 occupies 40 percent of the volume and has a density 

 of 1.1, one finds after making the appropriate calcu- 

 lations that the quantity of lithium approaches 5 

 billion pounds. It thus appears that the Foote 5-10 



billion estimate applies to the entire 32-square-mile 

 basin, and that the lower figure is to the known 

 depth of brine in existing wells and the higher 

 figure is to the probable average depth of the bottom 

 of the basin. The grade apparently was assumed to 

 be constant throughout the basin, and no estimate 

 was made of how far the lithium content can be 

 depleted before the grade becomes too low for profit- 

 able operation. The quantity, if any, of lithium that 

 is being added to the brine from lithium-bearing clay 

 and nearby hot springs, which would enlarge the 

 reserves, seems to be regarded as too small to take 

 into account. 



With this background, it is possible to place the 

 reserves and resources in categories. Probably 

 500,000 tons of lithium (20 percent of 5 billion 

 pounds) in and near existing wells over a thickness 

 of 600 feet can be called proved and probable re- 

 serves. Another 2 million tons of lithium at the 

 same depth extending outward to the borders of 

 the basin can be called possible reserves or condi- 

 tional resources. The remaining 2,500,000 tons (or 

 5 billion pounds) of lithium seems best categorized 

 as hypothetical resources. 



For Searles Lake, Calif., published data have been 

 used to make one estimate of 75,000 tons of LiaO 

 (Kesler, 1960, p. 524) and another of 90,000 tons 

 of LiaO (Norton and Schlegel, 1955, p. 346-347), 

 or about 40,000 tons of lithium. Because lithium is 

 only one of many products from Searles Lake, the 

 question of how much of it will be extracted depends 

 on the outlook for the rest of the operation. Pro- 

 duction is about 100 tons of lithium annually (Smith 

 and Irwin, 1966, p. 234). If, at the present rate of 

 operation, the deposit has a life of 100 years, which 

 seems as good an estimate as any that can be made 

 from the host of figures available, then the ultimate 

 output of lithium will be 10,000 tons. This amount 

 can be labeled reserves, and the remaining 30,000 

 tons known in the deposit can be called conditional 

 resources. 



The few other lithium brines that have been 

 identified have yielded very large resource estimates. 

 Conditional resources of 1,100,000 tons of lithium 

 are in the Salton Sea geothermal brine, which con- 

 tains several other constituents of potential eco- 

 nomic value (White, 1968, p. 313). The Salar de 

 Atacama, Chile, is said to have 1,200,000 tons of 

 lithium (Mining Jour., June 26, 1970, p. 597). Guil- 

 lermo Chong (written commun., Aug. 21, 1972) 

 confirms this estimate but says that an exploration 

 program is now starting. Until this exploration is 

 completed and the extraordinarily high supposed 

 content of 2,000 ppm lithium is substantiated, the 



