MINERALOGY AND COMPOSITION OF HISTORICAL Cu SLAGS FROM THE RUDAWY JANOWICKIE MOUNTAINS, SOUTHWESTERN POLAND

Abstract

Two types of slags produced during historical smelting of Cu ores occur in the Rudawy Janowickie Mountains, southwestern Poland. The prevailing massive slag has a chemical composition dominated by FeO (up to 51 wt.%), SiO 2 (up to 43 wt.%) and Al 2 O 3 (up to 12 wt.%). It consists of silicate glass, olivine and hercynite. The second type, a porous slag, is poorer in FeO (up to 28 wt.%) and richer in SiO 2 (up to 70 wt.%). It comprises two types of silicate glass, olivine, ferrosilite and SiO 2-group minerals (cristobalite and quartz). The morphology of the olivine crystals, phase assemblages, phase composition and distribution of trace elements in slag phases vary from sample to sample, which is consistent with different cooling rates. Phase diagrams used in this study indicate that most of the slag samples have solidified under conditions of strong disequilibrium caused by rapid cooling. A careful investigation of cooling conditions is essential to predict a susceptibility of slags to weathering and to reconstruct historical smelting conditions. For example, samples with longer cooling times are more resistant to weathering; they should be used to reconstruct the temperature of slag formation. Our mineralogical and chemical study of the Rudawy Janowickie slags and a comparison with other historical slags in Europe indicate that: (i) the temperature of slag formation was ca. 1200°C and overlaps with temperature ranges estimated for other historical slags, (ii) the furnace charge was either self-fluxing or silica was added as a flux, which is not so common for historical Cu slags, but was observed for smelting of Pb and Ag ores in the Czech Republic, (iii) preliminary roasting of furnace charge was efficient, as in other historical Cu-smelters, and (iv) the furnace atmosphere was reducing, also as in other historical smelting processes.

Characterization and pH-dependent leaching behaviour of historical and modern copper slags

“…According to information found in a source material describing the history of the area, industrial activity has been taking place there since the XIV th century up to first decade of XX th century (Kierczak & Pietranik, 2011).…”

“…Historical slags analyzed in this study refer to the massive slags described by Kierczak and Pietranik (2011). They were collected from the disposal site located in the Rudawy Janowickie Mountains (south-western Poland) representing a historical mining and smelting site.…”

Environmental impact and potential utilization of historical Cu-Fe-Co slags

“…There are several options of metal value recovery including crushing, grinding, magnetic separation and flotation operations, and leaching and roasting processes (Altundogan et al 2004;Arslan and Arslan 2002;Durinck et al 2008;Muravyov et al 2012;Sarrafi et al 2004;Shen and Forssberg 2003;Yin et al 2014). Residual amounts of the metals in the historical slags vary depending on the efficiency of the historical smelting technologies (Ettler et al 2009a;Kierczak and Pietranik 2011), and some of historical slags display even a lower residual content of metallic elements compared to those observed in modern slags (Potysz et al 2015b). The insignificant total concentration of metals in some slags calls for their use as cement additives which is a better option than their disposal (Frias et al 2006;Potysz et al 2015b;Rodríguez-Mendoza et al 2012).…”

“…In contrast to Cu slags, the weathering features such as presence of secondary Fe oxides were observed. In addition, enhanced leaching of Pb, Ni, Cu, and As indicates the lability of the glassy matrix (Ettler et al 2001;Kierczak and Pietranik 2011;Parsons et al 2001). In comparison to the Cu slags, the greater porosity of the ferrous slags promotes the exposure of the surface to weathering and causes swifter weathering (Ettler et al 2009b).…”

Mineralogy of the ceramic slags from the Bronze Age funerary site at Lăpuş (NW Romania)

“…The shape and the com po si tion of our slag pieces do not support a re la tion to metal smelt ing (see e.g., Serneels, 1995;Serneels and Crew, 1997;Buchwald and Wivel, 1998;An der son et al, 2003;Degryse et al, 2003;Rehren et al, 2007Rehren et al, , 2012Kierczak and Pietranik, 2011;Sharp and Mittwede, 2011). If they would have been re sult of e.g., iron pro cess ing, they should have 35-75 wt.% FeO (Buchwald and Wivel, 1998) and would con tain high amounts of Fe sil i cates.…”