UNITED STATES MINERAL RESOURCES 



GALLIUM, GERMANIUM, AND INDIUM 



By Robert A. Weeks 



CONTENTS 



Page 



Abstract of conclusions 237 



Introduction 237 



Principal uses 238 



Alternate materials 238 



Problems in development of commercial uses 239 



Resource availability 239 



Exploitation - 240 



Relation to other coproducts or byproducts 241 



Environmental relationship 241 



Geologic environment 241 



Geochemistry 241 



Abundance 242 



Ore minerals 242 



Types of ores 243 



Sulfide ores 243 



Bauxite 244 



Coal deposits . 244 



Resources 244 



Reserves 245 



Potential resources 245 



Prospecting techniques 245 



Problems and needs for additional research 246 



Selected bibliography 246 



TABLES 



45. 



48. 



Selected properties of gallium, germanium, and 

 indium 238 



Estimated production, price, and apparent de- 

 mand for gallium, germanium, and indium 239 



Gallium, germanium, and indium contents of 



various materials 241 



Gallium, germanium, and indium contents of 

 selected ore minerals and of reported gallium, 

 germanium, and indium minerals 243 



ABSTRACT OF CONCLUSIONS 



Known exploited sources of gallium, germanium, and in- 

 dium are largely the ores of zinc and aluminum, from which 

 they are recovered as minor byproducts. Potential additional | 



sources are copper ores, tin ores, and combustion products 

 of coal. The high cost of recovery and refining of gallium, 

 germanium, and indium limits their use to relatively small 

 quantities, mainly in transistors, diodes, and other electronic 

 devices. 



The geologic potential for finding deposits that could be ex- 

 ploited solely for their gallium, germanium, or indium con- 

 tent is very small. The potential for discovery of ores of other 

 metals from which gallium, germanium, or indium could be 

 recovered is significant. The potential for recovery of gallium 

 and germanium from coal ash, flue dust, and stack gases in 

 industrial plants consuming large quantities of coal is large. 



INTRODUCTION 



Gallium, germanium, and indium are three rela- 

 tively rare metallic elements that occur in accessory 

 or trace amounts in many rocks and minerals, in- 

 cluding some in ores of other metals. Commercial 

 recovery of these minor metals is, at present, en- 

 tirely as a byproduct in the processing of major 

 metallic ores, primarily zinc and aluminum, and to 

 a lesser extent copper and lead. 



There are no known deposits in which these metals 

 are sufficiently concentrated that they are apt to be 

 the principal product sought. None of them occur 

 as native elements, and they are essential compo- 

 nents in only a few very rare minerals. Their total 

 value is small or even negligible in relation to the 

 value of the principal metals with which they are 

 associated. They are deleterious impurities and must 

 be removed in refining the major metal. The com- 

 plex technology for their recovery is economically 

 feasible only if, at some stage in the processing of 

 the major metal, the minor metal or metals become 

 concentrated in a separable phase. The costs of their 

 separation and purification are significant, and so 

 recovery is limited to the amount of each that can 

 be marketed. A further problem associated with such 

 potential byproduct materials concerns the lack of 

 data about the variability of specific individual ore 

 sources, inasmuch as the processing plants do not 

 normally maintain records for such minor constitu- 



U.S. GEOL. SURVEY PROF. PAPER 820 



237 



