Gallium in Corundum from Deposits of Various Genetic Types

Corundum α-Al2O3 is a rare component of certain metamorphic and igneous rocks. Corundum contains trace elements Cr, Ti, Fe, V, Ga, Si, Mg, Be, etc. replacing Al in the octahedral position. Corundum forms isostructural series with some oxides of these elements due to the proximity of their ionic radii. In addition, the radius of the trivalent aluminum ion is very close to the ionic radius of trivalent gallium, and, as a result, we can expect an isomorphic replacement of aluminum with gallium. Gallium is a rare metal that is widely used in radio electronics and the semiconductor industry. Five modifications of Ga2O3 have been established, where one of them, α-Ga2O3, is isostructural to corundum. The authors studied the main trace elements (Be, Mg, Ti, V, Cr, Fe, and Ga) in corundum from various deposits across the world, using in situ laser ablation inductively-coupled plasma mass-spectrometry (LA-ICP-MS). The maximal amounts of this element are found in corundum of magmatic genesis, and the highest Ga values of 370 μg/g were recorded by the authors in corundum of the Ilmenogorsk complex. The detected gallium content in corundum from this object is almost 25 times higher than the Clarke number. Literary data showed that the Ilmenogorsk corundum contains the largest amount of gallium among primary deposits of blue corundum worldwide. According to our data, the concentration of gallium in nepheline from the underlying urtites of apatite-nepheline rocks within the Khibiny deposit is 50 g/t. Meanwhile, in Russia, more than 70% of Ga production comes from apatite-nepheline ores with an average element content of about 24 g/t.