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

This study presents the first complete reconstruction of gold metallurgy in Zloty 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 degrees C, and crystallization of the slags took place until they cooled to < 1200 degrees C. The morphology of olivine crystals in the slags indicates large differences in their cooling rate, from 5 to 300 degrees C/h. Strongly reducing conditions during the metallurgical process (-10.5 to -11.5 log fO(2)) was confirmed. Low melt viscosity (log(n) = 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 Zloty Stok to be corrected.

Automated summary

This study provides a complete reconstruction of gold metallurgy in Zloty Stok, Poland, using the analysis of metallurgical slags. The results reveal important parameters of the process and correct existing descriptions of the smelting process.