GALLIUM, GERMANIUM, AND INDIUM 



245 



the three metals. Ores of metals other than zinc 

 and aluminum, especially some copper and tin ores, 

 appear to have interesting concentrations of one or 

 all of these metals and might become important 

 sources. Recovery of germanium and some gallium 

 from industrial coal ash, flue dusts, and stack gas 

 is feasible and would increase the recoverable re- 

 coverable resources of these two metals signifi- 

 cantly. 



RESERVES 



The U.S. Bureau of Mines has estimated the re- 

 coverable supplies to the year 2000 for these three 

 metals, on the basis of 1968 technology and prices, 

 and projected demands for the major metals with 

 which they are associated, as follows: 



United States World 



(kg) (kg) 



Gallium : 



Total potential in bauxite 

 and zinc ores likely to be 



produced to year 2000 2,700,000 Not available 



Recoverable 27,000 Not available 



Germanium: recoverable from 



lead-zinc ores 375,000 1,360,000 



Additional potential, assuming 

 recovery from coal con- 

 sumed in industrial plants - 545,000 4,500,000 

 Indium: recoverable from 

 lead-zinc ores (assumes 

 some increase in zinc 

 prices) 1,460,000 3,360,000 



These estimates are necessarily conservative in 

 that present low recovery ratios have been used 

 and no new technology is assumed. Some uncertain- 

 ties have been introduced in these figures by the 

 closing of several older U.S. zinc smelters in the 

 period 1970-72, which resulted in the reduction of 

 domestic zinc smelting capacity by as much as a 

 third. The figures provide at least the order of 

 magnitude for amounts of the three metals that 

 may be obtained in the next few decades at expected 

 prices and using present technology. The figures 

 suggest that any potential new uses requiring large 

 amounts might require an associated increase in 

 production through better technology or exploitation 

 of additional sources. 



POTENTIAL RESOURCES 



On the basis of a simplistic assumption that all 

 sphalerites contain gallium, germanium, and indium 

 and that the estimated zinc reserves are all present 

 as sphalerite, calculation of the amount of these 

 three metals using median figures given in table 48 



suggests that about 2 million kg of gallium, 13.5 

 million kg of germanium, and 1.8 million kg of 

 indium might be contained in the recoverable por- 

 tion of identified U.S. zinc resources described in 

 the zinc chapter of this volume. If presumed identi- 

 fied resources are also included, these figures would 

 be approximately three times larger. World identi- 

 fied recoverable zinc resources would contain on the 

 order of 10 million kg of gallium, 70 million kg of 

 germanium and 9 million kg of indium. 



About 2,400,000 kg of gallium may be present in 

 identified domestic bauxite resources, and 12-18 

 million kg of gallium in potential domestic resources. 

 World resources of gallium contained in bauxite are 

 probably on the order of 50 times larger than the 

 domestic resources just cited. 



The amounts of gallium and germanium that 

 might be contained in coal combustion products are 

 less easily estimated, but the U.S. Bureau of Mines 

 estimate suggests about 500,000 kg of germanium 

 could be obtained from coal used in U.S. industrial 

 plants, with a world figure at about 10 times that 

 amount. 



The potential for recovery from ores of other 

 metals has not been enumerated. At least for ger- 

 manium, the content in identified domestic copper 

 ores containing significant enargite, tetrahedrite, 

 and tennatite might exceed 160,000 kg. On a world 

 basis, the gallium, germanium, and indium contents 

 of copper and tin ores are too poorly known to esti- 

 mate their additional potential. 



PROSPECTING TECHNIQUES 



Prospecting techniques for each of the major re- 

 sources with which gallium, germanium, and indium 

 are associated are described elsewhere in this volume 

 and will not be repeated. Even if major new uses for 

 one or all of these elements were to be developed 

 that would require greatly expanded production and 

 associated price increases, there is very little geo- 

 logic probability of finding ores that will be ex- 

 ploited solely for their gallium, germanium, or in- 

 dium contents. 



Much information needs to be obtained and natu- 

 ral distribution patterns need to be defined before 

 specific guides can be determined for each element. 

 Their geochemistry is still imperfectly understood, 

 especially the variability of each within specific 

 deposits and the range of variability in different 

 geologic settings. The accumulation and analysis of 

 such data is the next logical step in estabhshing a 

 better basis for identifying favorable deposits and 

 estimating resource availability. 



