422 



UNITED STATES MINERAL RESOURCES 



5-50 meters of pegmatite that is rich in potash 

 feldspar and mica (Shmakin and others, 1971). 



Most prospecting is still done by prospectors who 

 have developed their own criteria for finding mica 

 through years of experience. The success of the 

 Indian mica industry is in part the result of low 

 labor costs that have permitted intensive and con- 

 tinued prospecting for new deposits by individual 

 prospectors. For every 100 pegmatites that the In- 

 dians find, however, only two or three prove rich 

 enough to develop for commercial mining (Raj- 

 garhia, 1951, p. 49). This ratio of productive to 

 nonproductive pegmatites seems applicable to the 

 world supplies. 



PROBLEMS FOR RESEARCH 



The principal problems of the mica industry are 

 the high cost of hand labor needed for mining and 

 processing of sheet mica and the increasing use of 

 substitutes or decreasing need for sheet mica be- 

 cause of improved technology. The U.S. Bureau of 

 Mines forecasts a drastic reduction in sheet mica 

 needs by the year 2000 (Petkof, 1970, p. 1093), 

 and there is little reason to believe that sheet-mica 

 mining will ever again be important in the United 

 States. With the decrease in mining and processing 

 of sheet mica, the amount of high-quality scrap will 

 also decrease. Increased use of synthetic mica as a 

 substitute for coarser scrap in reconstituted mica 

 can be expected. Large supplies of high-quality scrap 

 probably will be available from India as long as the 

 sheet-mica industry is active there. In the United 

 States, a need for scrap- or flake-mica sources closer 

 to the active industry could be met by continued 

 evaluation of mica schist deposits that are outlined 

 by regional geologic mapping. 



SELECTED REFERENCES 



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Amos, D. H., 1959, DMEA project blossoms into best U.S. 

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Broadhurst, S. D., and Hash, L. J., 1953, The scrap mica re- 

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Brobst, D. A., 1962, Geology of the Spruce Pine district, 

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