224 



UNITED STATES MINERAL RESOURCES 



varies according to consumer demands but generally 

 contains 85-96 percent CaFj and has limits on SiOs, 

 CaCOs, Fe203, sulfide sulfur, lead, and zinc. Metal- 

 lurgical-grade fluorspar (metspar) is commonly 

 listed in market quotations as 60, 70, and 72.5 effec- 

 tive CaF, units; effective CaFs unit is a measure 

 obtained by multiplying the SiOa content of the ore 

 by 2.5 and subtracting this figure from the CaFa 

 content of the ore. Specifications for metspar usually 

 set maximum limits of 0.3 percent sulfide sulfur and 

 0.25-0.5 percent lead. Consumers desire metspar in 

 the form of lumps or gravel having no fines and a 

 maximum size of about 2 inches. Pellets and briquets 

 made from fines and flotation concentrates are now 

 replacing lump and gravel metspar in the United 

 States. It is significant from an economic standpoint 

 that metspar is used virtually as it occurs in nature, 

 fluorite (CaFj) plus impurities. 



Fluorspar as a flux in steel making accounts for 

 33 percent of the U.S. fluorine demand; fluorspar 

 as an iron foundry flux, a nonferrous metals flux, 

 and an additive in electrometallurgy accounts for 

 8 percent. Several possible substitutes for fluorspar 

 in steel fluxing have been tried, including calcium 

 chloride, bauxite and colemanite (hydrated borate 

 of calcium). None of these appears to be usable on 

 a large scale, but a concentrated effort is being 

 made by the steel industry to develop a usable syn- 

 thetic flux. 



Cryolite (NaaAlFg) and synthetic aluminum fluor- 

 ide are essential in the manufacture of aluminum 

 metal. Most cryolite used is synthetic and is made 

 by combining caustic soda, alumina, and hydro- 

 fluoric acid, or is prepared from waste solutions 

 containing 15-25 percent fluosilicic acid recovered 

 in manufacture of superphosphate. 



Natural or synthetic cryolite is the major flux 

 used in reducing alumina to aluminum metal in 

 electrolytic cells, and this use accounted for about 

 18 percent of the U.S. fluorine demand in 1968. Not 

 all the fluorine is lost in this process, and progress 

 is being made in recovering some of the fluorine 

 volatilized or wasted. This practice may reduce 

 slightly the acid-grade fluorspar requirement from 

 the present 135 pounds per ton of aluminum pro- 

 duced. The use of lithium carbonate as an additive 

 in aluminum manufacture also seems to reduce the 

 fluorine consumption. 



Fluorine consumed in the United States is mainly 

 in the form of fluorspar, 44 percent; hydrofluoric 

 acid (fluorocarbons), 35 percent; hydrofluoric acid 

 (cryolite), 18 percent; and fluosilicates, 3 percent 

 (MacMillan, 1970, p. 993). The production of fluoro- 

 carbon compounds has only recently reached its 



present consumption level and will probably remain 

 a major consumer of fluorine for some time. Fluoro- 

 carbon compounds are used in many ways — refrig- 

 erants, aerosol propellants, solvents, and special-use 

 plastics — and demand for fluorine is expanding 

 rapidly as new uses of these unique compounds are 

 developed. Fluorocarbons conceivably could be re- 

 placed in part by liquid nitrogen and compressed 

 gaseous nitrogen, which are readily available now 

 as byproducts of liquid-oxygen production. Fluorine 

 used in the ceramic, glass, welding-rod, and enamel 

 industries constituted about 6 percent of the U.S. 

 fluorine demand in 1968. 



In 1970 the United States accounted for about 6 

 percent of the world's production of fluorspar but 

 consumed 30 percent of this production. Thus in 

 that year the United States produced only 20 per- 

 cent of the fluorspar it consumed ; the other 80 per- 

 cent was imported mainly from Mexico, Spain, and 

 Italy. In the recent past the United States produced 

 only 15 percent of its consumption of fluorine; the 

 1970 increase probably reflects in part the release 

 by the U.S. Government of large amounts of stock- 

 piled acid-grade fluorspar. 



EXPLOITATION 



Until recently, fluorspar was virtually the only 

 source of fluorine, and it will probably remain the 

 major source in the near future. A relatively minor 

 amount of the fluorine consumed is at present being 

 recovered from the processing of phosphate rock, 

 which, along with other byproduct and coproduct 

 sources, will become increasingly important in the 

 future. Though data are not readily available, the 

 amounts of byproducts recovered from fluorspar 

 mining in the past apparently were not significant. 

 Sulfide concentrates — mainly lead, zinc, and silver — 

 are recovered in some operations, and barite is re- 

 covered as a coproduct in a few operations. 



Since World War II (fig. 26) world fluorspar pro- 

 duction and U.S. fluorspar consumption have in- 

 creased greatly, whereas U.S. production has 

 remained nearly static. The great increase in fluor- 

 spar consumption reflects the worldwide increased 

 production of steel and aluminum and the utiliza- 

 tion of fluorocarbons in many new industries. 



GEOLOGIC ENVIRONMENT 

 GEOCHEMISTRY 



Fluorine (atomic number 9, atomic weight 19) 

 consists of a single isotope occurring in nature 

 mostly as a singly charged anion, F-, but also oc- 

 casionally as a compound of complex anions, such 

 as (BF4) -. Fluorine is a gaseous element, and large 



