FLUORINE 



231 



fluorspar. Similar deposits of phosphate rock, with 

 estimated reserves totaling more than 10 billion tons 

 and enormous hypothetical resources, occur mainly 

 in Morocco, Tunisia, Algeria, Turkey, U.S.S.R., Peru, 

 China, North Vietnam, and Australia. Potentially 

 several hundred thousand tons of fluorine annually 

 could be obtained as a byproduct of phosphate pro- 

 duction in the United States. The estimated quantity 

 of fluorine discarded or lost during the processing 

 of phosphate rock in the United States approximates 

 the annual fluorspar imports into the United States 

 (Blake and others, 1971). In recent years more than 

 100,000 tons of hydrofluosilicic acid was recovered 

 in the United States during the manufacture of 

 superphosphates and was used mostly for water 

 fluoridation ; however, some of this acid is now proc- 

 essed further into aluminum fluoride and synthetic 

 cryolite for the aluminum industry and into fluosili- 

 cates. Fluorine from phosphate rock for the alumi- 

 num industry will become more competitive with 

 fluorspar in the next few years, as fluorspar prices 

 rise, as the demand grows, and as the phosphate 

 industry strives to control environmental pollution 

 near processing plants by recovering the fluorine. 

 Industrial plants in the United States, Mexico, 

 Canada, U.S.S.R., Austria, Rumania, India, and 

 Japan now use waste hydrofluosilicic acid from the 

 processing of phosphate rock, and other plants are 

 planned for France, West Germany, Switzerland, 

 and Australia. (See also the chapter on "Phosphate 

 Deposits" in this volume.) 



Topaz, although rarely concentrated, occurs in 

 probable commercial quantity and grade in at least 

 two localities in the United States. At the old 

 Brewer gold mine in South Carolina, reserves were 

 estimated at about 100,000 tons of schist averaging 

 approximately 15 percent topaz and about 1,200 tons 

 of topaz in adjacent placer deposits that contain 

 1-24 percent topaz. The hypothetical resources at 

 this deposit are estimated at about 800,000 tons of 

 ore. In the Front Range, Colo., a lens in Precambrian 

 gneiss containing about 15 percent topaz was esti- 

 mated to constitute a reserve of about 600,000 tons 

 of topaz-bearing rock. The hypothetical resources of 

 this topaz-bearing rock are estimated to be about 

 250,000 tons for every 100 feet of depth. 



Bastnaesite in carbonatite at Mountain Pass, 

 Calif., is a potential resource of fluorine. This rare- 

 earth mineral contains about 7 percent fluorine and 

 constitutes 5-15 percent of the carbonatite rock. 

 On the basis of an estimated 100 million tons of 

 potential ore at Mountain Pass (Olson and others, 

 1954), about 1 million tons of fluorine is estimated 

 as a potential byproduct of rare-earth extraction. 



SPECULATIVE RESOURCES 



Exploration for and evaluation of fluorine re- 

 sources must be based upon the geology and geo- 

 chemistry of fluorine. The important geologic param- 

 eters are regional tensional faults or other deep- 

 seated structures, alkalic and silicic igneous rocks, 

 carbonatites, and hydrothermal activity — including 

 hot springs. Fluorine is apparently very mobile in 

 geologic settings characterized by these parameters, 

 and in addition to forming deposits directly related 

 to those features, it also has moved into other geo- 

 logic environments associated in time and space to 

 form deposits there. For example, fluorine mobilized 

 by exhalations or weathering has been transferred 

 from the alkalic igneous rocks and carbonatites 

 along the African rift structures into the lake brines, 

 to be concentrated in evaporites of the rift valleys. 

 Fluorine-bearing solutions genetically related to the 

 important geologic parameters have permeated 

 country rock, such as the altered and mineralized 

 volcaniclastic sedimentary rocks of the Western 

 United States; have replaced receptive country 

 rocks, as in the Illinois-Kentucky district; and have 

 filled subsidiary fractures, in places some distance 

 from the igneous activity and major structures, as 

 in many smaller fluorspar districts of the Western 

 United States. 



The important geologic parameters listed above 

 define environments and processes in which fluorine 

 was available in abnormal amounts in some part of 

 the system and in which it could be mobilized and 

 transported into concentrations of economic interest. 

 Geologic processes in other environments also have 

 acted to concentrate minor amounts of fluorine (of 

 the order of crustal abundance) into deposits of 

 economic interest, as in the precipitation of fluorapa- 

 tite from sea water. 



These principles assure us that numerous possi- 

 bilities exist for the discovery of new resources of 

 fluorine. The best possibilities are undiscovered but 

 geologically predictable fluorine districts; known 

 small, but high grade, deposits ; and very large low- 

 grade multicommodity ores. At this time it is im- 

 possible to give a quantitative indication of specu- 

 lative resources, other than that they are probably 

 very large. 



In the United States new fluorspar districts might 

 be found northwest of the important Illinois- 

 Kentucky district in carbonate rocks beneath the 

 cover of Pennsylvanian rocks, and also northeast of 

 this district toward Ohio and the Michigan basin 

 beneath Pleistocene cover where fluorite occurrences 

 are known in Silurian and Devonian dolomites. Simi- 

 larly the Paleozoic carbonate rocks of central Tennes- 



