Hydrothermal Synthesis of Galloepidote—Analogue of Phase Ca2Al2Ga(Si3O12)(OH) from the Tykotlova Gold–Sulfide Occurrence

Resumo

Abstract—Solid solutions of the epidote–galloepidote series stable at defined P–T parameters were synthesized for the first time in order to reconstruct the crystallization conditions of gallium epidote analog Ca₂Al₂Ga(Si₃O₁₂)(OH) from ores of the Tykotlova gold–sulfide occurrence. The unit cell parameters of these phases were calculated and their IR and Raman spectra were obtained. It was concluded that gallium is mainly incorporated into M3 site, which makes it possible to consider the galloepidote as independent mineral species. Stable Ga-bearing aluminosilicate and silicate phases were obtained in the Ca–Ga–Al–Fe–Si–O system (analogs of grossular–andradite garnets and Ca feldspars) as the by-products of synthesis.