## 4 Conclusions  
Surface screening of the slag samples with a hand-held XRF spectrometer confirms that, compositionally, they are highly heterogeneous. Elemental compositions suggest the different provenance of the raw materials. Chemical composition as well as structural analyses permit affirming that at least bloom refining and processing of the refined iron took place on the sites. The slag cakes found could be byproducts of the refining process carried out in pit-furnaces [34]. The Fe dominancy in all the samples (even in the Vat sample which is the poorest in iron) can be attributed to the presence of a significant quantity of metallic globules (probably alloyed iron) embedded in the slags and formed during primary and/or secondary smithing. Mineralogically, archaeological iron slags are a heterogeneous mixture of silicates (olivines like fayalite, pyroxenes like hedenbergite), iron oxides (wustite, magnetite), amorphous material (mostly glass phases), and alteration products (like goethite). The FTIR spectral data indicate the presence of mineral phases expected in different (primary and/or secondary) smithing slag types. Corresponding to the PXRD data, in accordance with the FTIR results, besides the generally dominant quartz and a relatively great amount of amorphous, mostly glassy material, the main mineral phases of the Brancovenesti and Calugareni samples are the pyroxene hedenbergite, the iron oxyhydroxoxide goethite and the iron oxide magnetite--while, in the case of the Vatava sample, the same iron oxides and (not seen by XRD) the olivine fayalite. PXRD and FTIR results suggest that the studied slags can be considered primary or secondary smithing debris (metallurgical waste produced in the last steps of the smithing operations carried out by the blacksmith). Primary smithing slags are generated during the refining of the bloom, and secondary smithing slags are formed during the manufacturing and/or repair of artifacts [26]. The PXRD identified minerals are formed as the result of a complex smithing process supposing different temperature regimes. Hedenbergite, the predominant pyroxene of the slags from Brancovenesti and Calugareni, is segregated at crystallization temperatures ranging from 700 to 900 \({}^{\circ}\)C; olivines (the fayalite appearing on the diffractogram recorded on the Vatava sample--see Figure 2) crystallize at 1100-1200 \({}^{\circ}\)C; the presence of cristobalite also indicates the achievement of high temperatures during the metal processing. The quartz found in all samples derives most probably from flux addition. The most frequent iron oxide phase, associated with minor amounts of magnetite, is wustite, practically degraded during burial. The omnipresent weathering mineral goethite is formed in the course of wustite oxidation [31; 34]. The EPR spectra are able to properly prove the presence of Fe\({}^{3+}\) ions in the samples, the method allowing the determination of the Fe\({}^{3+}\)/Fe\({}^{2+}\) ratio in fair agreement with the chemical analysis data and the mildly reducing conditions of the slag solidification indicated by the amount of goethite (formed mostly by wustite oxidation during burial) typically present in the samples. **Author Contributions:** Conceptualization, E.B. and S.-P.P. ; methodology, E.B., S.-P.P., and E.V. ; investigation, data curation I.K., C.T., G.B., D.T. and Z.K.-B. ; resources, E.B. ; writing--original draft preparation, E.V., I.K., C.T., G.B., and Z.K.-B. ; writing--review and editing, E.B. and S.-P.P. All authors have read and agreed to the published version of the manuscript. **Funding:** The PXRD: FTIR and EPR measurements were financially supported by the Romanian Ministry of Research and Innovation, Core Program, Projects PN 19 35 02 01 and PN19 35 02 03. **Acknowledgments:** The archaeometric (archaeometallurgical) research carried out is part of the Project for Technical and Cultural Heritage Preservation in Transylvania, initiated and supervised by the Research Institute of the Transylvania Museum Society.