M. Járó - L. Költő szerk.: Archaeometrical research in Hungary (Budapest, 1988)
Analysis - HEGEDŰS Zoltán: Conclusions of metallographic tests on the production methods of bronze articles and slags
By reason of these difficulties a number of metallographic slag tests are not sufficiently exact, for example you can see in the following [7]: "The texture of the slag consisted of three phases: of a light grey phase constituting the base material; of a dark grey phase consisting of embedded needles or dendrites, and lastly the latter, with metallic reflecting light dendrites, embedded into the light-grey base material." In the following we give some important characteristics, which frequently appear in the iron slags. Wiistite (FeOJ: This is dove-grey coloured in comparison with iron, and in comparison with the silicates it is a light-grey ball, drop or dendrite, and in general it forms roundedged inclusions. It is black in a dark field and anisotropic in polarized light. Magnetite (FeO • Fe 2 0 3 ) and spinell (FeOM 2 0 3 ) which are more dark coloured in comparison with wiistite, and have more or less angular inclusions or indistinctly shaped ore remainders. They are in a dark field black coloured and in a polarized light isotropic and hard . Partly reduced ore remainders: They have very diversified optical properties and structures, and practically every single inclusion differs from another. Very complicated structures sometimes occur, and their identification by ore-microscopy [8,9] is extremely difficult. The partly reduced ore remainder visible on Photo 4 (unetched, N = 200x) was found in slag No. 12. Its structure: hematite (A), reduced magnetite (B), initial fay alite formation (C), the hematite contains undetermined needle crystals. Fayalite 2FeO'Si0 2 : In comparison with the other silicates it is more light-grey coloured, often with columnar or needle-like crystals. In a dark field it is illunrinating, and is anisotropic in polarized light. Silicate glasses: Their composition varies between wide limits and their colour depends on the (Fe Mn) 0 content; in a dark field they are ihuminating (the darker their colour, the greater their ihumination). On the basis of their colour they are classified in three groups: - light-grey glass, - moderate dark-grey glass, - dark-grey coloured glass. The light-grey and the moderate dark-grey silicates often mtermix. The dark-grey silicate constitutes with wiistite a locally separated eutectoidal structure (Photo 5; slag No. 1, N = 600x). The eutectic structured enclave is located in the light-grey glassy silicate. Table II shows the etching of the silicates and of wüstites by etcliing agents which are not applied in metallographical tests. The silicates of the single slags are sometimes etched more strongly, or more slightly, depending on the composition. The textures of the 20 slag types are summarized in Table III. Finally, we have to discuss the subsequent surface mineralization of the slags, too. On the surface, or in the larger cavities of some slags (e. g. No. 17) a subsequent lamellar surface alternation occurs, which is characteristic of the "gossan" structure. Its identification is easy, and before chemical analysis it must be removed; however, sometimes the removal is a difficult procedure. Testing of the reducibility of slags Crucibles of good quality refractory unmgs were filled with pieces of slag: in reality with pulverized slag mixed with five times the amount of charcoal. This was then covered with heat resistant clay and thereafter these specimens were put into a laboratory furnace and heated between 1000 and 1300 °C for one hour. Then the crucibles were cooled down in the furnace.
