548 



UNITED STATES MINERAL RESOURCES 



USES 



The rare earths are the basis for a small but in- 

 creasingly important industry that had its origin 

 about 100 years ago when rare earths were used as 

 a minor constituent in thorium gas mantles. The 

 annual domestic consumption of rare-earth oxides 

 is now more than 10,000 tons, compared with about 

 2,000 tons a decade ago. Most of the rare earths 

 used ai'e in the form of oxides, chlorides, or fluorides 

 of one or more of the major members of the cerium 

 subgroup — that is, cerium, lanthanum, neodymium, 

 and praseodymium — derived from bastnaesite or 

 monazite ores. Yttrium and the less abundant lan- 

 thanides, notably europium, are used to a lesser 

 extent but, because of their higher cost, contribute 

 disproportionately in dollar value to the industry. 

 Yttrium has been extracted from several source 

 materials including residues from the processing of 

 Idaho euxenite for niobium, Canadium uranium 

 ores, monazite, and xenotime. The rarer lanthanides 

 may be obtained from bastnaesite ores or from any 

 of the sources of yttrium just mentioned. 



Uses for the rare earths are diverse and are based 

 largely on the physical rather than the chemical 

 properties of the group. The major use at present is 

 in petroleum-cracking catalysts, in which rare earths 

 replace sodium in a synthetic zeolite structure. 

 Adoption of this type of catalyst began about 1964 

 and has contributed greatly to the expansion of the 

 rare-earth industry. Next in importance is the use 

 of rare earths in the glass and ceramic industries, 

 where they are used in the form of oxides, chlorides, 

 or fluorides for a variety of purposes, including 

 polishing materials, opacifiers, colorizers, and de- 

 colorizers, and as inhibitors of radiation coloration 

 in television-tube glass. Rare earths are used in 

 both ferrous and nonferrous metallurgy, sparking 

 alloys, and carbon-arc electrodes. Research into the 

 properties of individual rare-earth elements has led 

 to many new uses within the past decade. These 

 have been based largely on their optical and lumi- 

 nescent characteristics related to their unusual 

 atomic structure. Applications are in phosphors for 

 color-television tubes and high-intensity lighting, 

 in lasers, and in synthetic rare-earth garnets for 

 microwave systems. Permanent magnets of excep- 

 tionally high coercive strength are being made using 

 intermetallic compounds of rare earths and cobalt, 

 of which SmCos appears to be the most promising. 

 These and other uses of the rare earths are more 

 fully discussed by Parker and Baroch (1971) and 

 by Cannon (1972). 



New uses for rare earths undoubtedly will follow 

 technological advances in many fields, and by the 



same token, some present uses will become obsolete. 

 Research into catalysts for automobile exhaust 

 emission control has indicated that compounds of 

 rare-earth elements and certain transition elements, 

 notably the compound LaCoOa, hold considerable 

 promise (Libby, 1971). Adoption of such catalysts 

 would, of course, create an unprecedented demand 

 for the rare earths, as well as for cobalt. Another 

 potential application of rare earths that could 

 greatly increase their usage is in the removal of 

 phosphates from wastewater. Discharge of phos- 

 phate-bearing wastewater into streams and lakes is 

 a major cause of the "death" of bodies of water 

 through eutrophication, and only a small percentage 

 of the phosphate is removed by present water- 

 treatment plants. A method that offers almost com- 

 plete removal by precipitation as a rare-earth phos- 

 phate was described by Recht, Ghassemi, and 

 Kleber (1970). 



AVAILABILITY 



The rare earths are comparative newcomers 

 among the elements used by industry, and the extent 

 to which they are employed by a country reflects to 

 some extent the degree of sophistication of its tech- 

 nology. If rare earths were to become unavailable, 

 the effect on our present standard of living would 

 not be catastrophic because, in most applications, 

 the rare earths are merely replacing other materials 

 that are less effective for the particular purpose. 

 Without rare earths we would have inferior color 

 television, camera lenses, and cigarette-lighter flints ; 

 far more serious might be the effects felt in the 

 fields of glass manufacture, communications, ceram- 

 ics, and the iron and steel industry, and less gaso- 

 line would be produced per barrel of crude oil. 



Since the development of the bastnaesite deposit 

 at Mountain Pass, Calif., the United States has 

 become largely self-suflScient in rare-earth resources. 

 Bastnaesite, however, is a cerium subgroup min- 

 eral, and it contains only a very small percentage 

 of yttrium and the yttrium subgroup lanthanides. 

 Recent demands for these elements, notably yttrium, 

 have been met by their extraction from (1) resi- 

 dues from the processing of Idaho euxenite for 

 niobium, (2) monazite from beach placer deposits, 

 which is chiefly imported, and (3) residues from 

 Canadian uranium mills. Of these, the Idaho resi- 

 dues are now exhausted, and the recovery of rare 

 earths by Canadian uranium mills has been discon- 

 tinued. The present requirements for yttrium are 

 small, however, and appear to be adequately met by 

 stocks on hand and by existing sources. The United 

 States, therefore, is a potential exporter of the light 



