A feasibility study of portable spectroscopy for the analysis of mortar from the House of the Vestals
Wehby, Jennifer Leigh
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Mortar samples from the House of the Vestals, in Pompeii, Italy, were examined with traditional analytical techniques, including X-ray fluorescence, X-ray diffraction and thin section analysis. These techniques were used to establish mineralogical and chemical profiles of the samples and to verify the results of experimental field methods. Results showed the lime-based binder was composed of calcite, and the volcanic sand aggregate contained leucite, clinopyroxene, plagioclase, sanidine and olivine crystals. Field analysis of the mortar in situ consisted of nearinfrared (NIR) reflectance spectrometry with a portable FieldSpec 3 spectroradiometer. Key variances between samples fell within ~2000 – 2200nm and ~2250 – 2375nm, approximately where the major absorption bands appeared in a reference sample of pure calcite. This suggests the binder component of mortar is potentially useful for distinguishing different mortar types, and that this method of non-destructive analysis of the mortar in situ shows promise.