Reflectance Spectroscopy as a Tool for Identification of Historic Stone

Abstract. Within the research of historical stone monuments and artefacts we often encounter the question of determining the original material provenance. The answer to this question is often very complicated due to the frequent impossibility of taking samples for petrographic analysis, which in many cases cannot fully identify the place of origin. It is therefore necessary to pay attention to non-destructive survey methods applicable in the field. For the purpose of non-destructive stone provenance determination, the method of reflectance spectroscopy in the near and mid-infrared spectrum (1000–2500 nm) can be used. It is a very simple and effective method that can be implemented in-situ. This method is based on Earth remote sensing methods and is commonly used for the identification of minerals and soils, but it can also be used for the identification of rocks with a certain experimental set-up and a suitably chosen algorithm for the evaluation of the measured data. For each material, a unique spectral reflectance curve can be defined, which expresses the dependence between reflectance percentage and wavelength. The curve can then be compared with known spectra in a pre-prepared database to find the one that is most similar to the one under study and thus identify the material. The applicability of the method was verified, among other things, in the context of a survey of the historic stone masonry of the southern staircase of St. Vitus Cathedral in Prague, Czech Republic. Obtained results confirm the high potential of this method.