558 



UNITED STATES MINERAL RESOURCES 



by the use of bimetallic catalysts, such as platinum- 

 rhenium. Rhenium does not substitute for platinum 

 in the refining (rheniforming) process, but acts as 

 a promoter for the platinum catalyst. 



EXPLOITATION 



Rhenium is produced only in connection with the 

 industrial practice of roasting of molybdenite con- 

 centrates that contain about 100 to 2,000 ppm (parts 

 per million) rhenium (Churchward and Rosenbaum, 

 1963). Such concentrates are almost exclusively 

 those that are prepared as a byproduct from the 

 mining of the porphyry copper-molybdenum ores of 

 British Columbia, Western United States, Mexico, 

 Peru, Chile, and Russia. 



In the United States, current production of rhe- 

 nium, totaling only a few tons per year, comes from 

 its recovery from flue dusts that accumulate during 

 the conversion of byproduct molybdenite concen- 

 trates to molybdenum trioxide. 



Current technology permits recovery of rhenium 

 from those deposits in which the rhenium content 

 of the molybdenite is at least 100 ppm. 



Earliest recorded commercial production of rhe- 

 nium was in 1930 when small amounts of the metal 

 were recovered from copper smelter wastes at 

 Mansfeld, Germany. 



In the U.S. rhenium production began in 1942 at 

 the University of Tennessee, with the recovery there 

 of a few hundred pounds from smelter flue ducts 

 from the Miami Cooper Co.'s plant in Arizona; 

 sizable production did not begin until 1954 when 

 the Kennecott Copper Corp. began to recover rhe- 

 nium from some of the copper-molybdenum ores. 

 Annual production of rhenium increased markedly 

 during the early 1960's from about 1,000 pounds in 

 1962 to about 4,000 pounds in 1966, according to 

 annual reports of the U.S. Bureau of Mines. 



In 1960 the world's recoverable reserves of rhe- 

 nium were estimated to be greater than 500 tons, 

 U.S. reserves amounting to about 65 percent of the 

 total. World production in 1965 was about 5,000 

 pounds of rhenium. The price of rhenium has 

 ranged widely over the years, from $400 to $800 

 a pound. 



RESOURCES 



The principal rhenium resources consist of trace 

 amounts occurring in the molybdenite that accom- 

 panies the copper ores of porphyry copper deposits. 

 Rhenium is also present in the molybdenite of the 

 porphyry molybdenum deposits, in contact-meta- 

 morphic tungsten-molybdenum deposits, molybde- 

 num-bearing pegmatites, and molybdenite-bearing 



quartz veins. It also occurs with molybdenum and 

 uranium in bedded deposits in sandstone, in bitu- 

 minous copper-bearing shales, in vanadiferous black 

 shales, and in cupriferous sandstone deposits. 



The molybdenites of porphyry copper deposits 

 contain from about 100 to 3,000 ppm rhenium, sev- 

 eral times that in other types of deposits. Although 

 notable exceptions are known, in which rhenium 

 concentrations exceed 2,000 ppm, these exceptions 

 represent deposits containing tonnages too small to 

 be of economic significance under present conditions 

 (Peterson and others, 1959). 



Identified resources of rhenium in porphyry cop- 

 per deposits are estimated to be about 10,000 short 

 tons in the United States and on the order of 30,000 

 short tons in the entire world. These estimates are 

 calculated from the identified resources of molyb- 

 denite in porphyry copper deposits as detailed in 

 "Molybdenum" of this volume, assuming an aver- 

 age rhenium content of 800 ppm in the molybdenite 

 (=1,333 ppm Re in Mo) of such deposits. 



Because the only known readily available source 

 of rhenium is molybdenite, speculation as to addi- 

 tional resources must be related to molybdenum 

 resources. Nongeological factors, however, may op- 

 erate independently of the relation of rhenium to 

 molybdenum, to add significantly to the rhenium 

 resource base. Such factors include potential im- 

 provement in the technology of recovery, which may 

 make it possible to profitably recover rhenium from 

 the very large resources of molybdenite in the mo- 

 lybdenum porphyry deposits; improvements in 

 process metallurgy; and discoveries of new uses, 

 which may reduce costs of end products, with re- 

 sulting increase in demand for rhenium and possible 

 increase in its price. Owing to these factors and to 

 the variability of the rhenium content in molyb- 

 denite, any attempt at present to quantify the hypo- 

 thetical and speculative resources of rhenium would 

 have very little meaning. 



PROBLEMS FOR RESEARCH 



Considerable variation in rhenium content of 

 molybdenite from different parts of a deposit has 

 recently been noted. Determining average values 

 for rhenium in molybdenite in large deposits re- 

 quires analysis of many samples, still a time- 

 consuming and expensive process ; the only alterna- 

 tive today is to depend on analyses of mill concen- 

 trates for these average values. Further research 

 into analytical techniques seems warranted in order 

 to permit adequate sampling of the large low-grade 

 porphyry deposits, to delineate variations of rhe- 

 nium in molybdenite, and to obtain better under- 



