LITHIUM, CESIUM, AND RUBIDIUM 



369 



pegmatites as a rule contain either a great amount 

 of lithium or virtually none at all ; very small areas 

 can contain both kinds, with few or no pegmatites 

 of intermediate lithium content. This bimodal dis- 

 tribution indicates that the process of forming a 

 lithium-rich magma involves more than simple con- 

 centration of lithium in granitic magma. D. B. 

 Stewart (oral communs.), who has pondered this 

 problem at length, has suggested that minerals of 

 the granite, some of which can carry many hundreds 

 of parts per million lithium, returned their lithium 

 to the residual melt during reactions at a late stage 

 of magmatic crystallization. Whether a pocket of 

 residual melt could be in contact with, or have access 

 to, enough of the solidified granite to obtain the 

 requisite amount of lithium, and why it should 

 seldom if ever crystallize in place but instead be 

 expelled to crystallize elsewhere, are questions that 

 diminish the attractiveness of this ingenious pro- 

 posal. 



That the lithium-rich magma was derived from 

 granite magma, by processes not now understood, 

 remains likely, but it is by no means a certainty. 

 An alternate possibility is that lithium-rich magma 

 formed in the zone of anatexis, independently of the 

 granite magma, from partial melting of metasedi- 

 ments enriched in lithium. This origin is particularly 

 appealing for large pegmatites, such as those at 

 Kings Mountain, N. C, which have the same compo- 

 sition as at the minimum melting temperature in 

 the feldspar-quartz-spodumene system. If a body 

 of magma thus formed retains its individuality dur- 

 ing upward movement, it becomes a lithium-rich 

 pegmatite ; if it merges with nearby granite magma, 

 the result is granite with a somewhat higher than 

 normal lithium content. 



LITHIUM PEGMATITE LOCALITIES 



The known lithium deposits of the world are 

 numerous and widely distributed, but only a few 

 have been economically important. The outstanding 

 deposits are at Kings Mountain, N. C; Barraute, 

 Quebec; and Bikita, Rhodesia; and in the Karibib 

 and Warmbad districts of South West Africa. Many 

 other localities are known to be promising. Produc- 

 tion figures presented by Schreck (1961, tables 9- 

 12) provide a means of gaging the amount of lithium 

 mining during past years at places throughout the 

 world. 



UNITED STATES 



The dominant lithium district in the United States 

 is Kings Mountain, N. C, where an area about 25 

 miles long contains many spodumene-rich pegma- 



tites. The largest of these deposits, owned and mined 

 by the Foote Mineral Co., has been described in 

 detail by Kesler (1961). 



Other areas in the United States contain pegma- 

 tites that are rich in lithium but too small to com- 

 pete with equally rich but much larger deposits in 

 North Carolina. The foremost among these areas is 

 the Black Hills of South Dakota, which was the 

 main source of lithium in the United States before 

 the 1950's. All the production of the Black Hills has 

 been from relatively small well-zoned pegmatites. 

 The chief lithium mineral is spodumene, but the 

 output includes a moderate quantity of lepidolite 

 and most of the amblygonite mined in the United 

 States. Lepidolite has also been extracted at the 

 Harding mine near Dixon, N. Mex. ; at the Stewart 

 mine in the Pala district, California; and at the 

 Brown Derby mine in the Quartz Creek district, 

 Colorado. Other lithium pegmatites, most of which 

 contain spodumene as the lithium mineral, have been 

 found in Arizona, Wyoming, Massachusetts, New 

 Hampshire, and Maine. 



The Quebec Lithium Corp.'s spodumene mine at 

 Barraute, near Val d'Or, Quebec, is the most im- 

 portant of the known deposits in Canada and is the 

 only one with a record of large production. The 

 several pegmatites in this mine are virtually un- 

 zoned and consist mainly of albite, quartz, and 

 spodumene. 



The Tanco pegmatite (named from the Tantalum 

 Mining Corp. of Canada, Ltd.) at Bemic Lake, near 

 Lac du Bonnet, southeast Manitoba, which was 

 earlier known as the Chemalloy and still earlier as 

 the Montgary pegmatite, has drawn widespread 

 attention as a potentially important source of 

 lithium. This is a well-zoned i)egmatite in which 

 spodumene is the predominant lithium mineral but 

 in which lepidolite is also abundant (Hutchinson, 

 1959 ; Wright, 1963 ;Jiowe and Rowntree, 1966) and 

 petalite is present (Cemy and Ferguson, 1972). 



For the many other lithium pegmatites that have 

 been discovered in Canada, Mulligan (1965) is the 

 most comprehensive source of information. The Val 

 d'Or region, Quebec, and the region near Bemic 

 Lake, Manitoba, have attracted the greatest interest 

 and contain many of the deposits. Pegmatites at 

 Georgia Lake (Pye, 1965) and at several other locali- 

 ties in western Ontario carry spodumene. An exten- 

 sive area near Yellowknife, Northwest Territories, 

 has long been known to have lithium pegmatites, 

 some of which are well zoned (Mulligan, 1965, p. 

 85-87). Furthermore, in broad areas of the Cana- 



