UNITED STATES MINERAL RESOURCES 



FLUORINE 



By R. G. WoRL, R. E. Van Alstine, and D. R. Shawe 



CONTENTS 



Page 



Abstract of conclusions 223 



Introduction 223 



Exploitation 224 



Geologic environment 224 



Geochemistry 224 



Fluorine deposits associated with igneous rocks _ 226 

 Fluorine deposits associated with sedimentary 



rocks 227 



Fluorine deposits associated with metamorphic 



rocks 228 



Fluorine in hydrothermal deposits 228 



Resources 230 



Identified and hypothetical resources 230 



Speculative resources 231 



Prospecting techniques 232 



Problems for research 233 



References cited 233 



FIGURE 



Graph showing world production, 1913-70, U.S. 

 production, 1900-70, and U.S. consumption, 

 1911-70, of fluorspar 



TABLE 



44. Estimated fluorspar resources of the world 



225 



Page 

 230 



ABSTRACT OF CONCLUSIONS 



Fluorine is used by industry mainly as fluorspar (CaF») 

 for flux in steel making; as synthetic cryolite (NaaAlFo) and 

 aluminum fluoride in the manufacture of aluminum metal; 

 and as fluorocarbons in refrigerants, aerosol propellants, 

 solvents, and many other compounds. Fluorine consumption 

 in the United States and the world has increased greatly 

 since World War II, while fluorine production in the United 

 States has remained static. The United States produces only 

 20 percent of its requirement at the present. 



Fluorine in nature is dominantly in the combined form 

 and tends to concentrate in specific geologic environments. 

 Preferred igneous associations are silicic and alkalic extru- 

 sives and intrusives, complex pegmatites, carbonatites, and 

 contact aureoles of these. Sedimentary rocks containing con- 

 centrations of fluorine are volcaniclastic, lacustrine, evapor- 

 ite, marine carbonate, and marine phosphorite beds. Major 

 concentrations of fluorine occur in hydrothermal fluorspar 

 deposits. Hydrothermal deposits are distributed among a 

 wide variety of geologic environments in the form of veins, 

 mantos, stratiform beds, pipes, stockworks, and alteration 

 zones. 



Commercial sources of fluorine to date have been domi- 

 nantly hydrothermal deposits of fluorspar. Additional sources 

 in the future will be as byproducts from ores of other com- 

 modities, as coproducts of multicommodity ores, and from 

 fluorine deposits other than hydrothermal. A major future 

 source of fluorine will be as a byproduct of the processing 

 of phosphate rock, because fluorapatite (Ca6(POi,C03)sF) 

 is the major component of phosphate rock. 



World reserves of fluorspar (50 percent CaF~) are esti- 

 mated to be 190 million short tons, of which 25 million are 

 in the United States. Speculative resources of fluorine in 

 the world are probably very large. 



INTRODUCTION 



Fluorine, a versatile element, is widely used in 

 many industries and will probably remain in great 

 demand in the future. Present and potential sources 

 of fluorine are the major fluorine-bearing minerals 

 fluorite, cryolite, fluorapatite, and topaz. In this 

 report attention will be given mainly to fluorspar, 

 the ore of the mineral fluorite, until recently vir- 

 tually the only commercial source of fluorine. Syn- 

 thetic cryolite now has commercial value, but with 

 minor exceptions, other fluorine-bearing minerals 

 have not had commercial value. 



Fluorspar is marketed in three grades; acid, 

 ceramic, and metallurgical (Hodge, 1971, p. 10). 

 Acid-grade fluorspar contains a minimum of 97 per- 

 cent CaFa and a maximum of 1.5 percent SiO.. Lim- 

 its are commonly placed on other common impuri- 

 ties — CaCOs, sulfide sulfur or total sulfur, iron, 

 lead, zinc, and phosphorus. Ceramic-grade fluorspar 



U.S. GEOL. SURVEY PROF. PAPER 820 



223 



