474 



UNITED STATES MINERAL RESOURCES 



Table 94, — Identified thorium resources 



[Identified resources are specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

 may or may not be profitably recoverable with existing technology and economic conditions] 



Thousands of short tons ThO: 



Recover- Recoverable pri- 

 able marily for ThOs of 



primarily grade — 



as by- 

 product 



Type of deposit 



Principal published reference 



coproduct 



>0.1 

 percent 



<0.1 

 percent 



United States: 



Atlantic coast 



North and South Carolina 



Beach placer. 

 Fluviatile placer. 



16 



Idaho and Montana do 



Lemhi Pass district, Idaho and Montana. Veins. 



Wet Mountains, Colo do 



Powderhorn district, Colo do 



Mountain Pass district, California do 



— do Carbonatite. 



Palmer area, Michigan Conglomerate. 



Bald Mountain, Wyo do 



Total, United States 



Australia Beach placers. 



Brazil: 



Atlantic coast do 



28 



100.0 



4.5 



1.5 



.5 



___ McCauley (1960, p. 1). 

 56 Overstreet, Theobald, and 



Whitlow (1959, p. 713-714). 

 38 



U.S. Atomic Energy Comm. 



(1969, p. 127). 



46 Olson and Overstreet (1964, 

 P. 37). 

 2 Borrowman and Rosenbaum 

 (1962, p. 2). 



46 



106.5 



142 



Morro de Ferro, Minas (Jerais Alkalic rock 



complex. 



Araxa, Minas Gerais Carbonatite. 



Canada: Elliot Lake, Ontario Conglomerate. 



Greenland: southwest part Alkalic rock 



complex. 

 India; various areas, including Kerala, Bihar, 

 West Bengal Placers. 



Kenya: Mrima Hill, Mombasa area Carbonatite. 



Korea Fluviatile and 



beach placers. 



Malagasy Republic": Fort Dauphin area Beach placers. 



Malaysia Placers. 



Malawi Fluviatile and 



beach placers. 



South Africa': Palabora, Transvaal Carbonatite. 



Uganda: Sukulu, Eastern Province do 



United Arab Republic: Nile delta Fluviatile and 



beach placer. 

 West Africa: Nigeria, Sierra Leone Placers. 



60 

 20 



130 

 ■580 



460 



21 

 6 



10 

 20 



_„ Griffith (1964, p. 106). 



.__ Stamper and Chin (1970, 



p. 685). 

 Wedow (1967, p. 30) 



Guimaraes (1957). 



.._ Griffith and Roscoe (1964, p. 



11). 

 750 European Nuclear Energy 



Agency (1967, p. 13). 



Bhola and others (1965, p. 



93). 

 __. Davidson (1956, p. 206). 

 Olson and Overstreet (1964, 



p. 32-33). 

 ___ Murdock (1963). 



— Shortt (1970, p. 207). 

 10 Bowie (1959). 



— Pike (1958, p. 94). 



— _ Davidson (1956, p. 206). 

 Higazy and Naguib (1958). 



— Bowie (1959). 



Total world identified resources 1,435 



902 



' Not shown, because of inadequate data, are resources in Argentina, Ceyl 

 monazite veins), Uruguay, U.S.S.R., and several other countries. 



^ Includes some hypothetical resources, which are undiscovered mineral 

 predictable as existing in known districts. 



parts of Malagasy Republic, Norway, South Africa ( Steenkampskraal 

 whether of recoverable or subeconomic grade, that are geologically 



Knowledge of certain factors in the formation and 

 concentration of monazite can aid in the search for 

 undiscovered placers. Monazite commonly forms by 

 recrystallization during metamorphism, and the 

 thorium content of the monazite increases with the 

 grade of metamorphism (Overstreet, 1967). Mon- 

 azite weathered from metamorphic rocks is concen- 

 trated in the near-shore sediments laid down in the 

 ocean. If these sediments are raised above sea level 

 and are in turn eroded, monazite may be reconcen- 

 trated. Beaches in which the monazite has gone 



through more than one cycle of erosion and deposi- 

 tion, in general, have greater concentrations of mon- 

 azite than those that have gone through only one 

 cycle. Furthermore, more monazite is freed from 

 rocks where the enclosing minerals are thoroughly 

 weathered — for example, in warm, humid climates. 

 In arid climates the rocks do not weather as deeply, 

 and in the far north the monazite in the sediments 

 may be dispersed by glaciation. In the search for new 

 monazite beaches, effort should be concentrated in 

 areas in subtropical or tropical climates that have 



