An Unusual Corrosion Product, Kobyashevite, From Ancient Egyptian Copper Artifacts: Technical Note

Maher, Manal Ahmed; Ali, Yussri Salem

doi:10.21608/ejchem.2020.36950.2763

An Unusual Corrosion Product, Kobyashevite, From Ancient Egyptian Copper Artifacts: Technical Note

Document Type : Original Article

Authors

¹ Researcher in Post Graduate Studies College of Nanotechnology, Cairo University; Head of Computed Tomography X-Ray unit, Cairo Egyptian Museum, Ministry of Antiquities, Egypt

² Lecturer, Conservation Department, Faculty of Archaeology, South Valley University, Qena 83523, Egypt

10.21608/ejchem.2020.36950.2763

Abstract

Kobyashevite is one of copper sulfate hydroxide hydrate minerals “devilline group”. It forms as a thin coating crust in calcite and gypsum veins and it takes flower-like morphology and its color varies between the bluish-green to turquoise-blue. In the laboratory studies, it has been synthesized in humid atmospheric air containing sub-ppm of SO2. In the corrosion studies of archeological metals, it has not been identified before. Fortunately, the case study objects have never been undergone any conservation processes before, which gives originality of the analyzed samples and more accurate results. Scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray fluorescence, and Raman spectroscopy have been carried out in order to identify the corrosion samples. The present study identified a "kobyashviete" corrosion product for the first time in the archaeological studies on some archeological copper artifacts from the Egyptian Museum in Cairo. The study has been suggested that the formation of the unusual corrosion product "kobyashviete" is due to exposure the case study to uncontrolled long–term humid storage environment which has been contaminated with a high percentage of sulfur gases.

Keywords