GALLIUM, GERMANIUM, AND INDIUM 



243 



Table 48. — Gallium, germanium, and indium contents of selected ore m.inerals and of reported gallium, germanium, and 



indium, minerals 



Mineral name and composition 



Germanium 



Ore minerals (ppm) 



Sphalerite, ZnS 



Galena, PbS 



Chalcopyrite, CuFeSs 



Enargite, CuaAsSi 



Bornite, CusFeSi 



Tennantite, CuiiAsiSw 



Tetrahedrite, Cui2SbiSia 



Covellite, CuS 



Ghalcocite, GuiS 



Pyrite, FeSs 



Molybdenite, M0S2 



Stannite, OuiFeSnSi 



Cassitcrite, SnOa 



Wolframite, (Fe,Mn)W04 



Arsenopyrite, FeAsS 



Gallite, CuGaSi 



Sohngeite, Ga(0H)3 



Argyrodite, AgsGeSa 



Germanitc, Cu3(Ge,Fe)S4 



Renierite, (Cu,Fe,Ge,Zn) S 



Briarite, Cu2 ( Fe.Zn ) GeSi 



Stottite, FeGe(OH)a 



Fleischerite, PbsGe ( SO4 ) 2 ( OH ) e. 3H20 



1-10,000 

 0- 600 

 0- 100 



Median 

 40-60 



10 



Range 

 5 -1,850 

 0-10 

 0.6- 900 

 6,000 

 -1,000 



Median 

 100-600 



Range 

 0.6-10.000 



Gallium minerals (percent) 



Germanium minerals (percent) 



As shown in table 48, sphalerite is the mineral in 

 which all three elements tend to be most concen- 

 trated. The exact nature of their incorporation into 

 the crystal lattice of sphalerite is not fully known, 

 but there do not appear to be distinct solid phases 

 of the sulfides of any of the three elements, and each 

 element is apparently able to proxy for zinc in the 

 limited amounts found. There is some evidence that 

 germanium and gallium contents are highest in the 

 low-temperature varieties of sphalerite and that in- 

 dium content is highest in medium-temperature 

 varieties of sphalerite. Thus, zinc ores from low- 

 temperature deposits such as the upper Mississippi 

 Valley and Tri-State districts tend to have among 

 the highest reported gallium and germanium con- 

 tents but not the highest indium content. 



Other sulfide minerals that have major concentra- 

 tions of germanium are chalcopyrite, bornite, enar- 

 gite, and tennantite. Major concentrations of indium 

 have been reported in cassiterite, especially in the 

 "wood tin" variety, in which the concentration may 

 typically exceed 0.5 percent indium. Stannite, an- 

 other tin-bearing mineral, also has been reported to 

 contain significant indium concentrations. 



TYPES OF ORES 



The present major sources of gallium, germanium, 

 and indium are zinc and bauxite ores, which are 

 more fully described in the chapters on zinc and 

 aluminum resources. 



SULFIDE ORES 



Far too few data are available to indicate the 

 variation in distribution of any of the three elements 

 in specific zinc deposits or within districts or broader 

 regions. The sparse data suggest that there may be 

 geologic provinces in which one or all of these ele- 

 ments are relatively more abundant in the inter- 

 mediate to silicic igneous rocks, and that late-stage 

 pneumatolytic and hydrothermal deposits associated 

 with these rocks might be correspondingly enriched. 

 The relatively higher gallium and germ.anium con- 

 tent noted in sphalerites formed at lower tempera- 

 tures indicates a beginning of attempts to unravel 

 the specific distribution patterns for these elements. 



The geologic environment most favorable for large 

 zinc sulfide ore deposits is in sedimentary sequences 

 which include carbonate rock strata that have been 

 permeated by mineralizing solutions. The source of 



