Mineralogy of copper slags of Ekaterinburg Metallurgical Plant

Research subject . Copper slags of Ekaterinburg Metallurgical Plant, founded in 1723 and discontinued in 1808. Materials and methods . Copper slags were collected from an archaeological excavation site in the Historical Square of Ekaterinburg. The material composition of the slags was studied in the Laboratory of Physical and Chemical Research Methods of the Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences (Ekaterinburg). The chemical composition of minerals and their photographs were taken using a TESCAN MIRA LMS, S6123 scanning electron microscope with an INCA Energy 450 X-Max 80 energy-dispersive attachment from Oxford Instruments. X-ray phase analysis of the slag was performed on an XRD-7000 X-ray diffractometer from Shimadzu. Results. The studies showed that copper slags are represented by different types – pyroxene, fayalite-wustite, and pyroxene-fayalite. The first type is composed of a homogeneous aggregate of augite with the presence of glass, magnesiochromite, copper, and covellite. The second type is represented by fayalite and wustite with the presence of glass, copper, and idaite, as well as cuprite, barite, and atacamite. The third type of slag is composed of hedenbergite and fayalite with the presence of glass, sulfides, as well as silver, gypsum, and secondary copper minerals (cuprite, atacamite, sampleyite, malachite, etc.). Conclusions. Such a variety of slags in a small excavation area confirms the available information about the various sources of copper ores for the Ekaterinburg plant. At the same time, it can be argued that both oxidized and sulfide copper ores were delivered to the plant. The latter came from the Shilovsky copper mine and were smelted at the Ekaterinburg plant in the first years of its operation. From these ores, slags of the third type were obtained, i.e., of fayalite-hedenbergite composition. Oxidized ores most likely originated from the Gumeshevsky mine (fayalite-wustite slag) and some unknown small mine from the area of the future large Pyshminsko-Klyuchevskoye deposit (pyroxene slag). An interesting technological trend at the Ekaterinburg plant was revealed: here, pyrites were first smelted and only then transition to oxide copper ores was made.