A close analog of aluminum, gallium is widespread in the earth's crust. It occurs almost entirely as a hydrated oxide in reconstituted minerals and comprises a rather constant proportion of all aluminum-bearing ores. In zinc and germanium ores, gallium may occur as the sulfide. Its most concentrated deposits (0.5% - 1%) have been found with South African germanite.

Gallium has been found concentrated up to 1% in flue dust as a result of the volatility of gallium suboxide. It has also been reported in concentrations up to 0.5% in coal ash. Gallium is not present in significant amounts in the sea or other natural waters because of the very low solubility of the oxide at near neutral pH.