Geochemistry, petrology and evolutionary computations in the service of archaeology: restoration of the historical smelting process at the Katowice–Szopienice site

Abstract

Activity at the smelting plant at Katowice–Szopienice dates back to the nineteenth century. Currently, the Museum of Zinc has been funded at the site. Unfortunately, as a result of unrest during both World Wars, all technological descriptions were lost. Three historically described samples were provided by Museum of Zinc and additional slag and lining samples were collected directly from the furnace. “Enriched ore” is dominated by ZnS (89.5%) as sphalerite and wurtzite accompanied by gangue minerals. “Roasted ore” is composed mainly of zincite (74%) resulting from the oxidation of ZnS. Study has proved that “roasted ore with coke” sample description is inappropriate. It is zinc depleted and enriched in Si (22.93 wt.%), Al (9.16 wt.%), C (9.66 wt.%) and its phase composition suggest that it contains recycled lining material and coke. Such characteristics place sample as additions used for smelting process. Advanced mathematical tool, the differential evolution algorithm, was used for restoration of smelting process at the site. Algorithm proved great usefulness by providing low dispersed results for calculated compositions of loss on smelting (mainly yield) with the fitting error reduced down to 1.19 wt.%. Loss on smelting composition was dominated by Zn (41.40 wt.%), Si (9.67 wt.%) and C (9.50 wt.%). Proportion of roasted ore to addition in smelting process was estimated as 1:1.27 and loss on smelting share from batch was 62%. Geochemistry and petrology have provided rich qualitative information about the samples and smelting process, but in combination with evolutionary computations, high-quality quantitative data were obtained.