アルメニア共和国ルチャシェン遺跡から出土した考古金属資料の腐食状態に閧する科学的調査

摘要

The National Research Institute for Cultural Properties, Tokyo and the History Museum of Armenia have been jointly conducting capacity development workshops on conservation of archeological metal objects which are part of the collection of the History-Museum of Armenia. This paper reports the results of scientific research in the conservation work of archeological metal objects in Armenia and those of additional research in Japan following the previous report. Objects studied are copper alloy ware excavated at Lchashen site in Armenia. These were produced during the Late Bronze Age (BC.15-BC.14) and show black overall. The surface products are observed to be hard and fragile. These features indicate the possibilities that the buried environment was not ordinary or that the materials used were particular. So scientific research was conducted for the purpose of inferring the corrosion process of these objects and clarifying their metal compositions. Optical microscope and scanning electron microscope (SEM) were used for observation. For elemental analysis, handheld x-ray fluorescence analyzer (XRF) and energy dispersive X-ray spectrometer (EDS) attached to SEM were used. In addition, the crystal structure was identified by X-ray diffractometer (XRD). As a result, it was found that the surface products of the objects include sulfur in great amount and that these are copper sulfide (I) (Cu2S) or a similar compound. Moreover, it was revealed that tin is unevenly distributed on the stripped side of the surface products. This means that copper did selective corrosion to sulfur. It can be considered that this was caused by a reaction to hydrogen sulfide generated by sulfate-reducing bacterium under an anaerobic environment. It was also found that the material of the objects is bronze generally used in this period.%アルメニア共和国ルチャシュン遺跡から発掘された資料の表面は，全体に黒色を呈し，その表面生成物は硬く脆い状態であることが観察された。これらの特徴は，使用された材料が特異的である可能性と，埋蔵環境が特異的であった可能性が考えられる。そこで，ルチヤシヱン遺跡出土の資料の腐食状態を明らかにすることにより，埋蔵環境の推定および使用された合金種の同定を行うことを目的として科学的調査を行った。