LITHIUM, CESIUM, AND RUBIDIUM 



377 



zation of oceanic salts, it is clear that rubidium in- 

 creases in concentration in the brine until very 

 nearly the end. The same applies as granite pro- 

 gresses to pegmatite, and the increase doubtless 

 continues to the late stages of crystallization of at 

 least some pegmatites, especially those containing 

 lepidolite and poUucite. 



Exhaustion of the stock of alkali carbonate re- 

 maining from lepidolite processing at San Antonio 

 will necessitate finding another source of rubidium. 

 This is not likely to be difficult if the demand con- 

 tinues small and the price high. Development of any 

 new large-magnitude use, beyond what can be sup- 

 plied from byproduct sources, will require search 

 for new deposits, which in all likelihood can be 

 found somewhere among the wide range of natural 

 substances containing concentrations of alkalis. A 

 discovery of rubidium-rich pegmatites in Manitoba 

 (Jambor and Potter, 1967) indicates that grades of 

 at least 1.0 percent RbaO are possible. The large 

 body of analytical data acquired throughout the 

 world in making rubidium-strontium age determina- 

 tions probably would provide useful leads to where 

 rubidium deposits might be found. At present, how- 

 ever, data pointing to potential rubidium deposits, 

 as well as data about future demand for rubidium, 

 and in what chemical form it might be used, are so 

 sparse that it is fruitless to attempt to estimate 

 resources. 



RESEARCH SUGGESTED 



Because supplies of lithium, cesium, and probably 

 rubidium are large relative to their market, there 

 is no urgent need to find new resources. New uses 

 for these elements are seriously considered from 

 time to time, and some of these uses could ultimately 

 create a large demand. To prepare for this even- 

 tuality, it would be prudent to learn more about 

 which rocks and waters have concentrations of these 

 elements and to identify the processes that cause 

 these concentrations, so that search for new depos- 

 its can, at any future time, be intelligently planned. 

 Geochemical investigations to date have been di- 

 rected mainly at rocks, minerals, and waters that 

 contain only slight amounts of these elements rather 

 than at those likely to become economically pro- 

 ductive, but they provide a basis for studies that 

 can clarify how deposits form and where they might 

 be found. 



A desirable objective of future research is to facili- 

 tate the discovery of higher grade lithium deposits 

 than those now known, so as to diminish cost of pro- 

 duction — or, on the other hand, to show that no such 

 deposits are likely to be found and all plans must be 



based on present costs. Lithium is unusual among 

 mineral commodities in that the known resources in 

 deposits of modest but minable grade are enormous, 

 yet resources in truly high-grade deposits have never 

 been found. This suggests that sizable high-grade 

 deposits do in fact exist but have been overlooked. 



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