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

Abstract

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, Fe 2 As), as well as glass. These slags are chemically dominated by SiO 2 (< 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 (À10.5 to À11.5 log fO 2 ) was confirmed. Low melt viscosity (log ƞ = 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.

Reconstruction of smelting conditions during 16th‐ to 18th‐century copper ore processing in the Kielce region (Old Polish Industrial District) based on slags from Miedziana Góra, Poland

“…proposed by Bachmann (1982) and modified by Ettler et al (2009). This method is widely used in the analysis of smelting slags (e.g., Derkowska et al, 2021;Kupczak et al, 2020;Warchulski, Warchulski et al, 2022) and takes into account the polymerizing to depolymerizing components ratio:…”

“…In this method, the melt temperature is included in the calculation, and the resulting values are in SI units (Pa s). This model was proposed for natural rocks, and it has also been successfully applied for slags (Ettler et al, 2009;Warchulski, Szczuka, & Kupczak, 2020;Warchulski et al, 2022). The model is based on the following equation:…”

“…Most of the available diagrams take into account three to four components, and not necessarily those present in the analyzed slags in significant amounts. There are also diagrams designed for minerals that take into account more components, but in that case the chemical composition of the analyzed material should correspond to the chemical composition of the phases for which they were designed (e.g., Warchulski et al, 2022). For this reason, it is necessary to use those matching best the chemical composition of analyzed slags.…”

“…The shaft furnace used for copper smelting in the 16th to 18th century was similar to those used in lead and gold metallurgy (Agricola, 1556;Warchulski, Szczuka, & Kupczak, 2020;Warchulski et al, 2022; Figure 6). The only difference was in the use of a different type of drive.…”

“…Thus, the end product of the process is a pure metal and a solidified silicate melt (slag) containing the remaining components (e.g., Warchulski, Gawęda, et al, 2020). In the past, slags were often stored in landfills and partially used in subsequent melts as fluxes (Agricola, 1556;US Congress, Office of Technology Assessment, 1988;Warchulski, Szczuka, & Kupczak, 2020;Warchulski et al, 2022).…”