552 



UNITED STATES MINERAL RESOURCES 



mated to contain only 0.057 percent total rare-earth 

 oxides (Jackson, 1968, p. 381), the production of 

 yttrium oxide averaged more than 100,000 pounds 

 per year during the 3-year period 1967-69. 



RESOURCES 



PRESENT SITUATION 



The rare-earth industry in the United States is 

 based largely on two main sources of raw mate- 

 rials — the bastnaesite deposit at Mountain Pass, 

 Calif., and imported ores, chiefly monazite, from 

 Australia and Malaysia. At times, these have been 

 supplemented by unusual source materials, such as 

 byproduct yttrium-rich residues from Idaho euxenite 

 and Canadian uranium mills. Inasmuch as such 

 sources have been ample to supply the 10,000 or so 

 tons of rare-earth oxides now consumed annually 

 in the United States, there is little incentive at pres- 

 ent to search for and develop new deposits or to 

 recover byproduct rare earths. 



By the year 2000, the annual domestic require- 

 ments may be nearly 25,000 short tons for lantha- 

 nide oxides and about 180 short tons (compared with 

 the present requirements of about 30 tons) for 

 yttrium oxide, as estimated by Stamper and Chin 

 (1970, p. 692, 801). The lanthanide requirements 

 probably can be met easily from sources that are 

 now being used, but the estimated sixfold increase 

 in yttrium demand might necessitate its extraction 

 from sources in the United States that have never 

 been used. Reactivation of yttrium recovery from 

 Blind River uranium mills can be anticipated, to- 

 gether with some increase over former production. 



POTENTIAL RESOURCES 



The foregoing discussion of types of rare-earth 

 deposits will give some indication of the variety of 

 environments in which the rare earths are likely to 

 occur. Environments most favorable for the discov- 

 ery of concentrations that could be mined solely for 

 rare earths are very limited and are primarily car- 

 bonatites and placers. Concentrations in gneisses 

 and migmatites so far discovered are currently of 

 marginal value but may eventually become signifi- 

 cant — particularly those containing xenotime, as at 

 Music Valley, Cahf. (Evans, 1964). When rare 

 earths are considered as byproducts or coproducts, 

 the field of potential producers is greatly expanded 

 and will include many additional carbonatites and 

 placers, both modern and fossil, thorite-bearing vein 

 deposits, apatite-bearing magnetite deposits, and 

 phosphatic rocks. Barite is a potential coproduct in 

 some rare-earth deposits, such as those at Mountain 

 Pass, Calif. 



Many carbonatites and related rocks in alkalic 

 complexes contain large tonnages of rare earths, 

 not only in dominantly rare-earth species, as at 

 Mountain Pass, but as proxying elements in other 

 valuable minerals, such as the niobium ore pyro- 

 chlore and the phosphate ore apatite. In at least one 

 foreign country, rare earths are currently being 

 produced as a byproduct in the processing of apatite 

 for fertilizer materials. 



The apatite common in metasomatic magnetite 

 deposits is generally high in rare earths, and such 

 deposits are likely future sources of these elements, 

 inasmuch as the apatite must be separated from the 

 magnetite prior to smelting. Dumps at Mineville, 

 N.Y., and Iron Mountain, Utah, contain large quan- 

 tities of apatite ; the Mineville apatite contains about 

 11 percent total rare earths (McKeown and Klemic, 

 1956, p. 6), and the apatite from Iron Mountain 

 contains about 3 percent. Increases in the use of 

 rare earths will make their recovery from this type 

 of deposit feasible. 



Another even larger untapped resource lies in the 

 sedimentary phosphatic rocks, where the rare earths 

 are also present in apatite. Such rocks are likely to 

 be a much lower grade source of rare earths than 

 apatite concentrates from carbonatites or iron de- 

 posits, but greatly exceed these in tonnage. Alt- 

 schuler, Berman, and Cuttitta (1967) pointed out 

 that in the national production of wet-process phos- 

 phoric acid in 1964, roughly 3,500 tons of elemental 

 rare earths was made available by the solution of 

 6 million tons of apatite. This exceeded by more 

 than 1,000 tons the domestic production of rare- 

 earth oxides from bastnaesite and monazite ores 

 during the same year. Altschuler's study of the 

 feasibility of rare-earth extraction from phosphor- 

 ites was based largely on phosphorite of the Bone 

 Valley Formation in Florida, which has an elemental 

 rare-earth content of about 0.06 percent. Higher 

 rare-earth values were reported by Gulbrandsen 

 (1966) for the phosphorites of the Phosphoria For- 

 mation in the Western United States ; his average 

 values for the Retort and Meade Peak Phosphatic 

 Shale Members are 0.1 percent yttrium, 0.03 percent 

 each for lanthanum and neodymium, and 0.001- 

 0.003 percent ytterbium. Other rare earths were not 

 included in the analyses. On the basis of these values, 

 the 4 million or so tons of phosphate rock mined 

 annually from the Retort and Meade Peak Members 

 could contain as much as 4,000 tons of yttrium alone, 

 more than 100 times the present demand. Reserves 

 of phosphate rock in the United States are on the 

 order of billions of tons. (See chapter entitled "Phos- 

 phate Deposits.") In the processing of phosphorites, 



