Indium is recovered almost exclusively as a byproduct of zinc. Estimates of the average indium content of the Earth's crust range from 50 to 200 parts per billion. The average indium content of zinc deposits ranges from less than 1 to 100 parts per million. The highest known concentrations of indium occur in vein or replacement sulfide deposits, usually associated with tin-bearing minerals. However, these types of deposits are often difficult to process economically.
Gallium arsenide can substitute for indium phosphide in solar cells and semiconductor applications.
Hafnium can replace indium alloys for use in nuclear reactor control rods. NA Not available. See Appendix C for definitions.