Thermal and mineralogical investigations of iron archaeological materials

In Covasna area from Romania, some heterogeneous metallurgical waste (slag) has been identified by archaeological excavations. This paper presents the analytical investigations of such an iron material, performed by inductively coupled plasma atomic emission spectrometry, energy dispersive X-ray fluorescence, X-ray diffraction and thermal analyses. From mineralogical point of view, the samples collected from the artefact are dominated by fayalite and almandine. Also, the slag has an iron-dominated composition, with magnetite, tridymite and quartz, too. Meanwhile, the ratios SiO 2 /Al 2 O 3 and K 2 O/MgO are rather low (1.2–2), these being further proof for assigning the sample to a slag one. Because CaO, MgO, and K 2 O have low concentrations, it may be concluded that another material has been used to melt the mineral than the usually used wood and coal, most probably charcoal. The presence of vanadium is a proof of iron production from magnetite ore or hematite. Glass factor (G factor) of the monolithic samples has low values, corresponding to almandine–fayalite–tridymite–glass composite. The performed thermal analyses materialized into valuable information regarding the composition of the analysed materials.