Innovative application of portable X-ray fluorescence (XRF) to identify Goktepe white marble artifacts

An efficient and non-destructive method to classify white marble artifacts by using a hand-held, portable XRF analyzer (pXRF) is here reported. The identification is based on the uniquely high strontium content of this marble and has been verified by testing 32 artifacts, most of which had already been provenanced, using conventional micro-destructive analyses. Besides strontium, other potential provenance indicators, such as manganese and iron, were analyzed and their concentration values obtained after empirical calibration of the instrument by using 17 quarry samples of known composition. The results show that Goktepe/non-Goktepe discrimination is almost always possible (30 artifacts) and that additional analyses are required only when the Sr value is at the lower edge of the G"oktepe field (2 artifacts). The success of the method, however, resides in the particular composition relative to trace elements of G"oktepe and is not easily extended to other marble varieties. Main reasons are related to insufficient accuracy at low concentration values, intrinsic trace variability of marble artifacts, surface effects that may produce not representative results. Interest in the method therefore is tightly linked to the exceptional importance of G"oktepe as a sculptural marble, in which case, detailed data, obtained with a fast and totally non-destructive method, may provide relevant information concerning chronology, workshops, and places of production of the artifacts.