Slag dumps are common in Upper Silesia landscape. Studied wastes from Katowice–Piekary Śląskie sites are a result of continuous ore smelting, waste storage and weathering for about 150 years. As a result we observe large variety of secondary phases, mostly in specific localization within slag dump, related to fresh exposure of material, but sheltered from direct external factors that may cause extensive rinsing and thus leaching of secondary phases. In this study we follow Brils et al.(2008) definition of secondary phases ie formed after primary ones crystallized from melt initially in the slag, on textural basis. As a result, among the secondary assemblage we can find also relatively high-temperature phases effected in deuteric and hydrothermal alteration. According to the XRD data (PANalytical X’PERT PRO; Co Kα1 radiation, 45kV voltage, 30mA intensity) and SEM-EDS (FET Philips XL30) investigations the secondary phases are represented by: carbonates (calcite–aragonite), hydrated carbonates (pyroaurite, lansfordite–hydromagnesite), sulfates and hydrated sulfates (anhydrite–gypsum), hydrated sulfate-carbonates (rapidcreekite) and oxides (hematite and zincite) and some other secondary phases. Gypsum in the studied slags forms anhedral or needle-shaped aggregates up to 5mm; barite with cerium and strontium enrichment is present as anhedral laths up to 50 μm; beudantite-like (PbFe3 [AsO4][SO4][OH] 6) sulfate-arsenate is present as anhedral grains up to 100 μm, with K and Ca substituting Pb; Ca-Al rich sulfate close to ye’elimite (Ca4Al6 [SO4] O12) or ettringite (Ca6Al2 [SO4] 3 [OH] 12· 26H2O) forms lath aggregates up to 70 μm; rapidcreekite is present as needle aggregates up to 3mm, or separate subhedral crystals up to 200 μm. Cerussite is locally fill the interstices in sulfides; phosphates with compositions close to harrisonite (Ca [Fe2+, Mg] 6 [PO4] 2 [SiO4] 2) or perhamite (Ca3Al7. 7Si3P4O23. 5 [OH] 14.1· 8H2O) showing enrichments in As and Zn form laths and columns up to 250 μm. Arsenate with nealite-like composition (Pb4Fe3+[As3+O3] 2Cl4· 2H2O) and Zn concentrations present as needle-aggregates up to 20 μm; anhedral AsFe component occurs with exsolved Fe droplets. Zincite forms pipe-like aggregates of lath crystals on slag surface. Since the secondary phases could be easily dissolved, they could be treated as the couse of potential environmental contamination.

Acknowledgements: Rafał Warchulski is the beneficiary of the “DoktoRIS–Scholarship program for innovative Silesia” co-financed by European Union under the European Social Fund and grant for young researchers under title “Weathering-induced element mobilization from Zn-Pb slags from Piekary Śląskie and its impact for soil chemistry”.