ERANDA GJEÇI, OLTA ÇAKAJ
KEYWORDS : coins, Albania, LIBS, XRF, elemental composition, Jaccard Similarity coefficients.
ABSTRACT :
Archaeological investigation is challenging, especially in coins’ cases, because of the sampling difficulties, at the same time, very important to understand the political and economic developments of a certain region and period. In this paper we studied seven coins excavated in a monument in the center of Durrës (ancient city of Epidamnos, Dyrrah), Albania. The study of these coins is done in collaboration with the archaeologists of the Archaeological Museum Durrës, although they were already damaged. The aim of this study is to investigate the alloy composition used in the cases of these coins, all excavated among other metallic objects in Durrës. Laserinduced breakdown spectroscopy (LIBS) and X ray fluorescence (XRF) were used to qualitatively determine the composition of the coins. All the objects of this study had a variety of compositions from pure Cu to Cu-Sn-Pb-Fe alloys. The elemental composition of the coins was compared with what was previously determined with µ – X ray fluorescence (µ-XRF). Qualitative results of the two methods were on average significantly similar, as affirmed by values of Jaccard Similarity coefficients calculated. These average values were 0.52 for µ-XRF – XRF of the UI, 0.65 for LIBS – XRF of the UI and 0.67 for LIBS – µ-XRF. LIBS qualitative composition of studied coins was also compared by means of respective Jaccard Similarity coefficients for each pair of coins. Results show significant similarity among coins. Coins with file no 8414, 8378, 8321, 8408 and 8342 show the highest average similarity with others, while the ones with file no 8382 and 8425 present the lowest.