Pb-Rich Slags, Minerals, and Pollution Resulted from a Medieval Ag-Pb Smelting and Mining Operation in the Silesian-Cracovian Region (Southern Poland)

Abstract

Since the 12th century in the Silesian-Cracovian area, lead, litharge, and silver have been produced by the pyrometallurgical processing of Pb-Ag-Zn ore. Slags and soils contaminated with heavy metals (Zn, Pb, Cd, Fe, Mn, As) were the subject of this research. Samples were collected during archaeological works in the area of early medieval metallurgical settlement. The main goals of the analyses (Scanning Electron Miscroscopy-Energy Dispersive Spectroscopy (SEM-EDS), Electron Probe Microanalyzer (EPMA), X-ray diffraction (XRD), Atomic Absorption Spectroscopy (AAS)) were the determination of the mineralogical composition of furnace batches and smelting temperatures and conditions. In soils, the anthropogenic phases enriched in Pb, Zn, Fe, Mn, P, and primary minerals like goethite, ferrihydrite, sphalerite, galena, smithsonite, minrecordite, cerussite, gypsum, anglesite, jarosite, and hemimorphite were identified. The soil from former metallurgical settlements contained up to 1106 mg·kg −1 Pb, 782 mg·kg −1 Zn, 4.7 mg·kg −1 Cd in the fine fraction. Much higher heavy metal concentrations were observed in the waste products of ore rinsing, up to 49,282 mg·kg −1 Pb, 64,408 mg·kg −1 Zn, and 287 mg·kg −1 Cd. The medieval smelting industry and Pb-Ag-Zn ore processing are marked by highly anomalous geochemical pollution (Pb, Zn, Cd, Fe, Mn, Ba) in the topsoil. The methods of mineralogical investigation, such as SEM-EDS or EMPA, can be used to identify mineralogical phases formed during metallurgical processes or ore processing. Based on these methods, the characteristic primary assemblage and synthetic phases were identified in the area polluted by medieval metallurgy and mining of Pb-Ag-Zn ores, including MVT (Mississippi Valley Type) deposits. The minerals distinguished in slags and the structural features of metal-bearing aggregates allow us to conclude that batches have included mostly oxidised minerals (PbCO 3 , ZnCO 3 , CaZn(CO 3 ) 2 , FeOOH), sulfides (PbS and ZnS) and quartz (SiO 2 ). The laboratory experiment of high-temperature heating of the examined slags showed that smelting temperatures used in the second half of 13th century were very high and could have reached up to 1550 • C. The results indicate, that geochemical and mineralogical methods can be used to obtain important information from archaeological sites, even after archaeological work has long ceased.Minerals 2020, 10, 28 2 of 16 mining and metallurgy centres since Roman times. In the period between the 10th and 12th centuries, iron, lead, tin, silver, and gold had become more important for the development of civilization in Central and Eastern European countries. Since the beginning of the 10th century in medieval Europe, in areas where ores of Ag-Pb, Au, As-Au, Cu, Sn and Fe occurr, mining centres have appeared, such as at the Ore Mountains (Erzgebirge), Harz Mountains, and Sudetes.One of Europe's largest Zn-Pb, MVT (Mississippi Valley) type ore deposits can be found in the Silesian-Cracow area (southern Poland) [1]. Shallow deposits are represented...

Ex novo development of lead glassmaking in early Umayyad Spain

“…Data on lead slag from various medieval European sites show a high compositional variability that depends on the primary ore, the addition of secondary reactants (total charge), and the stage of the smelting process at which the slag was extracted ( 42 – 44 ). The major and minor element compositions of the lead glass from Šaqunda are well within the compositional range of published data for lead slags ( 42 – 44 ). The presence of high barium and low silver levels in the Šaqunda samples corroborates the use of lead slag ( Fig.…”

Ołów w środowisku

“…Since the 12th century, many lead and silver smelting centres developed in the Silesia and Lesser Poland area in the vicinity of the silverrich galena deposits. Archaeological works enabled discoveries of blast furnaces, scrubbers, ores, slabs of crude lead, silver coins and many artefacts from lead, litharge or silver (Cabała et al, 2020;. Geological and mineralogical studies in the historical metallurgical settlements and ore beneficiation sites indicate that the local environment was contaminated with primary and synthetic lead minerals (Cabała et al, 2013;Cabała et al, 2020).…”

Reconstruction of 16th–17th Century Lead Smelting Processes on the Basis of Slag Properties: A Case Study from Sławków, Poland

“…In the centers of the historical metallurgical industry, we can observe remnants of metallurgical activities in the form of slags. They are a research topic in Poland [8,9] and in other European countries [10][11][12][13][14].…”

“…Geochemical, petrological and experimental methods can be used to approximate it. Numerous slag studies determined the smelting temperature based on phase diagrams [10,18,23,25,27], geothermometers [21,29,30], or laboratory experiments [8,18,31]. Other method require the construction of furnaces, similar to those used in historical times [11,12].…”

“…Low melt viscosity facilitated the process of separating of the metallic phase from the slag, which makes the metallurgical process more effective [31]. Geochemical and petrological studies can also approximate the furnace atmosphere [31] and addition in the smelting process [8,24,[32][33][34]. The charcoal fragments occasionally occurring in historical slags can be used to determine the type of wood used [12,28], and also by dendrochronological [35] and radiocarbon [12,28,35] methods to determine their age.…”