Synthetic Gold Chalcogenides in the Au–Te–Se–S System and Their Natural Analogs

Resumo

Quaternary chalcogenides of AuX (AuTe_0.7Se_0.2S_0.1), Au₃X₁₀ (Au₃Te₆Se₃S, Au₃Te₆Se_2.5S_1.5), and AuX₂ (AuTe_1.8Se_0.2, AuTe_1.8Se_0.1S_0.1) composition were synthesized for the first time in the Au‒Te‒Se‒S system, where Te ≥ Se + S. They are produced by dry synthesis upon heating a mixture of elementary substances with compositions of AuTe_0.666Se_0.167S_0.167 (X/Au = 1, X = Σ(Te + Se + S)), AuTeSe_0.5S_0.5 (X/Au = 2), AuTe₂Se_1.125S_0.375, AuTe₂Se_0.75S_0.75 (X/Au = 3.5), and AuTe_2.5SeS_0.5 (X/Au = 4) in vacuum quartz ampoules from 25–700°C and annealing at 400°C. According to XRD, the synthetic Au chalcogenides of AuTe_1.8(Se,S)_0.2 composition correspond to calaverite (α-AuTe₂). The unidentified XRD peaks belong to AuX and Au₃X₁₀. They are synthetic analogs of previously unknown natural compounds, which were found in the Gaching area of the Maletoivayam ore field (Central Kamchatka volcanic belt). The compositions of natural phases span the following ranges: Au_0.99–1.00Te_0.70–0.71Se_0.25–0.27S_0.03–0.06 and Au_2.91–3.08Te_5.85–6.06Se_1.57–3.66S_2.63–0.44. The Raman spectra of synthetic and natural Au chalcogendies close in composition are identical.