Kompozičně neobvyklé struskové hmoty z polykulturní archeologické lokality Boršice v podhůří Chřibů

We present results of laboratory investigation slag-like artifacts, found on an archaeological site near Boršice, known by occurrence artifacts from the Early Neolithic (5 700–5 000 BC), Bronze and Medieval Ages. The grey-coloured foamy reach up to 5 cm in size often display original lava-like surface. These slags are formed especially strongly potassic (15–23 wt. % K2O) silicic (54–72 SiO2) glass with elevated contents Ca (4–15 CaO), P (1–5 P2O5) Mg MgO) only traces Al, Mn Fe (below 0.14 oxides each these elements). Glass phase is partly altered due weathering, which caused hydration almost complete loss K. Sparse minute crystals wollastonite (CaSiO3) unidentified Ca-K-Si-P-O (with highly variable compositions poor stoichiometry) occur places phase. suggest that origin studied probably connected either modern or ancient production glass. However, it certainly not foam glass, industrially produced worldwide used waste Based average chemical composition we could originate smelting a mixture quartz sand, potash, bone ash, calcitic limestone (or marble) dolomite weight proportions equal 58.9, 24.6, 4.9, 3.3 8.3, respectively.