LITHIUM, CESIUM, AND RUBIDIUM 



375 



potential of this deposit seems best combined with 

 that of other Uthium brines that may exist in South 

 America to make an estimate of 1 million tons of 

 hypothetical resources. 



Great Salt Lake and probably other saline lakes 

 in the world contain enormous quantities of lithium. 

 Such lakes are omitted from table 73 because, un- 

 like the other deposits included in the table, they 

 are far more important for other purposes than as 

 mineral deposits, and the likelihood is small that 

 their lithium, which is at a very low grade, will be 

 extracted in large quantity for a long time, if ever. 



SUMMARY OF LITHIUM RESERVE;S AND RESOURCES 



Table 73 shows that the world has proved and 

 probable reserves of 1,200,000 tons of lithium plus 

 nearly 10 million tons of possible reserves, condi- 

 tional resources, and hypothetical resources. The 

 proved and probable reserves alone would last the 

 world 400 years at the 1970 rate of consumption. 



Most of the vast quantities of lithium itemized in 

 table 73 are in the United States, which suggests 

 that much larger resources exist but remain unde- 

 tected in foreign countries. By multiplying domestic 

 resources by 16.0, which is approximately the ratio of 

 the world's land area to that of the United States, 

 one finds that world totals can probaby be brought 

 to a level of 120 million tons of lithium. If domestic 

 resources are in fact greater than shown in table 

 73, which is likely, and if the rest of the world does 

 have proportionately as much lithium as the United 

 States, which is also likely, then the actual world 

 total is even larger. Any new discoveries are most 

 likely to be made in localities with pegmatitic rocks 

 in Canada, South America, Africa, and Australia, 

 and in brines of western North and South America 

 or geologically similar regions elsewhere. 



Lithium-resource estimates by this author have 

 sometimes been called conservative. They are in fact 

 neither conservative nor liberal, but are merely the 

 largest that can be projected from existing data. 

 The real meaning of table 73 is that resources of 

 lithium, in deposits comparable to those that have 

 been mined, are virtually unlimited relative to any 

 likely demand. If a truly large demand for lithium 

 ever arises — for example, for batteries for electric 

 automobiles or for nuclear-power generation, which, 

 however inevitable their development may be, will 

 not necessarily use much lithium — ^then the search 

 for high-quality lithium deposits will be renewed, 

 and resource figures will skyrocket even further. 

 Prudence would, of course, require that deposits be 

 identified and their reserves determined before any 

 such large use actually begins. 



CESIUM 



Cesium, though of low abundance in the earth's 

 crust, has large reservoirs relative to its exceed- 

 ingly small consumption. Most of the production 

 and nearly all the known reserves are attributable 

 to the Bikita pegmatite in Rhodesia, a few pegma- 

 tites in South West Africa, and the Tanco pegma- 

 tite, Manitoba. 



Uses that have most commonly been mentioned 

 are in research and development of ionic engines for 

 space travel and thermionic power generation, 

 which thus far at least has also been associated 

 chiefly with space flights. Otherwise the use of 

 cesium is in infrared lamps, photomultiplier tubes, 

 scintillation crystals, pharmaceuticals, and certain 

 chemical processes (Heindl, 1970, p. 530). 



GEOLOGY 



Cesium is most abundant in zoned pegmatites, a 

 few of which contain astonishingly large and rich 

 deposits. It is also concentrated in natural brines 

 during crystallization of salts from sea water, but 

 reaches a maximum of only 20 ppm in the last pre- 

 cipitates, sylvite and carnallite (Michael Fleischer, 

 written commun., 1972) . Two analyses of the Salton 

 Sea geothermal brine show 14 and 20 ppm cesium 

 (White, 1968, table 1). If any brines are 

 known to have greater concentrations of cesium, 

 the facts seem not to have been published. 



In pegmatites the most abundant (and for prac- 

 tical purposes, the only) cesium mineral is pollucite, 

 (Cs,Na) AlSi206, which in commercial concentrates 

 generally contains somewhat more than 20 percent 

 CsaO. Analyzed pure pollucite from the Tanco peg- 

 matite, which has the largest reserves, contains 

 36.2 percent CssO (Nickel, 1961, p. 6). Handsorted 

 material, because it is contaminated by quartz which 

 resembles pollucite, has about 28 percent CsaO in 

 the Tanco deposit (Hutchinson, 1959, p. 1534) and 

 about 25 percent at Bikita (Cooper, 1964, p. 451). 

 Other cesium-rich minerals include uncommon forms 

 of beryl (as much as 9.5 percent CsjO), cesium 

 kupletskite, avogadrite, and the rare borate rho- 

 dizite (Michael Fleischer, written commun., 1972). 



Pollucite deposits have a conspicuous association 

 with lithium pegmatites that contain lepidolite and 

 petalite. The Bikita and Tanco pegmatites have the 

 world's two largest lepidolite deposits and also the 

 two largest pollucite deposits. Similarly in South 

 West Africa, though the published record is not so 

 clear cut on the subject, the pegmatites with lepi- 

 dolite and petalite seem also to be the source of 

 pollucite. In both the Bikita and the Tanco pegma- 

 tites, most of the pollucite is in a single large and 



