232 



UNITED STATES MINERAL RESOURCES 



see and Kentucky are widely mineralized with fluor- 

 ite, as shown in recent drilling, and may contain 

 other commercial deposits. Large, but lower grade, 

 stratiform fluorspar deposits in carbonate rocks, like 

 those worked in the United States, France, U.S.S.R., 

 and southern Africa, probably will be popular tar- 

 gets for exploration. In the Western United States 

 fluorspar deposits undoubtedly underlie parts of the 

 widespread cover of Tertiary and Quarternary sedi- 

 mentary and volcanic rocks. Cenozoic tuffaceous lake 

 beds in the Western United States, Italy, and south- 

 ern Africa contain fluorite, some of commercial in- 

 terest, and other occurrences of this type of fine- 

 grained fluorite may have been overlooked. Some 

 fluorspar deposits of the Western United States are 

 related genetically to areas of silicic volcanic rocks, 

 namely the Big Bend subprovince of Texas ; the Naci- 

 miento subprovince of Arizona, New Mexico, and 

 Colorado; and the Shoshone province of Nevada, 

 Utah, Idaho, and Montana. Other areas with rela- 

 tively high fluorine content in volcanic rocks might 

 be worthy of further prospecting, especially south- 

 eastern Idaho, northwestern Wyoming, and north- 

 western Utah. In west-central Utah, topaz is dissemi- 

 nated in volcanic rocks, and commercial fluorspar 

 deposits are distributed around the southern and 

 western periphery of a caldera. Only a third of the 

 caldera is exposed ; the remainder, which is covered 

 by rhyolite flows or alluvium, may contain undiscov- 

 ered deposits (Shawe, 1972, p. B76-B77). A tectonic 

 unit consisting of the Rio Grande trough in New 

 Mexico, and its northern extension through Colo- 

 rado, Wyoming, and Montana, is especially rich in 

 fluorspar deposits and should be explored further. 

 Deposits of syngenetic fluorite associated with gyp- 

 sum and limestone are reported from Permian ma- 

 rine evaporites in the Big Horn Mountains, Wyo. ; 

 similar extensive deposits are known in the Permi- 

 an of U.S.S.R., and other equivalent evaporites 

 should be investigated for deposits of fluorite. 



Large deposits of fluorapatite in marine phosphate 

 rock probably exist beneath the sea in Tertiary 

 coastal plain sediments extending east from deposits 

 in North and South Carolina and Florida. Fluorine 

 is recovered from huge deposits of fluorapatite in 

 alkalic rocks of U.S.S.R., and other deposits of this 

 type may be found and profitably explored elsewhere. 



Probably milhons of tons of topaz-bearing rock 

 are yet to be discovered in widespread metamorphic 

 terranes throughout the world. Because cryolite, 

 NasAlFe, is a rare mineral, it probably will not be 

 an important source of fluorine; the world's only 

 known commercial deposit of natural cryohte, in 

 Greenland, has been depleted. Sodium fluoride has 



been found in saline lake beds in Tanganyika and 

 may some day be a source of fluorine. 



Some brines, volcanic gases, fumaroles, and hot 

 springs with relatively high fluorine contents may 

 suggest fluorine-rich provinces in which deposits of 

 fluorspar, phosphate rock, or other fluorine materials 

 should be sought. Deep sea sediments, which have 

 more fluorine than most other marine sediments 

 except phosphate rock, contain about 0.07 percent 

 fluorine; these types of sediments and sea water it- 

 self, which has about 0.0001 percent fluorine, may 

 be sources of fluorine in the distant future. 



Numerous high-grade but small deposits of fluor- 

 spar, such as those of the Western United States, 

 might be utilized. This use would require better 

 techniques of locating and evaluating small pods of 

 fluorspar and the use of portable extraction and 

 processing equipment. Even though this type of 

 mining may not be feasible now in the Western 

 United States, because of high labor costs and land 

 problems, it might be elsewhere in the world. 



Very large low-grade multicommodity ores oflFer 

 potential fluorine resources. These include deposits 

 in which fluorine, mainly in the form of fluorite, is 

 associated with metallic minerals (see discussions 

 of geochemistry and exploitation) and those in 

 which it is associated with or contained in other 

 minerals of commercial interest, such as barite, 

 bastnaesite, apatite, zeolites, and feldspars. It may 

 be possible in the future to process such multicom- 

 modity ores, in which no single commodity is of 

 high enough grade to be commercial. 



PROSPECTING TECHNIQUES 



Fluorspar deposits commonly have been found by 

 identification of fluorite in outcrops and surficial ma- 

 terials. The durability of fluorite during weathering 

 and the high fluorine content of the mineral suggest 

 that some geochemical methods might be useful in 

 prospecting for fluorspar. Nevertheless, geochemis- 

 try has not been widely used, in part because of the 

 lack of rapid analytical procedures for determining, 

 with the necessary reliability and low cost, the fluo- 

 rine contents of samples. 



A fluorine halo could be meaningless in fluorine 

 exploration, inasmuch as fluorine is widely dis- 

 persed in many mineralized and altered areas other 

 than those containing fluorine-rich deposits. Path- 

 finder elements can be used as a guide to some fluo- 

 rine mineralization. To use this guide, however, 

 requires considerable geologic knowledge of the area 

 being surveyed. This approach avoids the problem 

 of low-level fluorine analysis but will be successful 

 only where the pathfinder element is consistently 



