Complete reconstruction of the process and conditions during gold smelting in the 15th–17th centuries in Złoty Stok based on metallurgical slags.

This study presents the first complete reconstruction of gold metallurgy in Złoty Stok, Poland. The key parameters of the process (i.e., temperature of smelting and solidification, melt viscosity, oxygen fugacity) are calculated using the remnants of the process: metallurgical slags. The slags consist of silicate phases (i.e., olivine, pyroxene), sulfides and arsenides (i.e., pyrrhotite, Fe2As), as well as glass. These slags are chemically dominated by SiO2 (< 56.60 wt%), MgO (< 18.36 wt%), FeO (< 15.36 wt%), and CaO (< 15.19 wt%). The obtained results indicate that the temperature during the metallurgical process was at least 1300–1350°C, and crystallization of the slags took place until they cooled to < 1200°C. The morphology of olivine crystals in the slags indicates large differences in their cooling rate, from 5 to 300°C/h. Strongly reducing conditions during the metallurgical process (−10.5 to −11.5 log fO2) was confirmed. Low melt viscosity (logƞ = 0.26 – 0.90 Pa s) facilitated the separation of the sulfide melt rich in gold from the silicate melt being the slag precursor. The obtained results allowed existing descriptions of the smelting process in Złoty Stok to be corrected. [ABSTRACT FROM AUTHOR]