The ruins of Pompeii, Italy, having been well preserved, allow a unique opportunity to study architectural styles, techniques, and materials on a large scale. The structures in this ancient city consist of volcanic stones set in mortar, a lime-based cement mixed with volcanic aggregate. Visual analysis is often useful for identifying different types of mortar that represent individual construction phases within a single structure. However, visual analysis alone may not be adequate for distinguishing mortar types that are similar in color or composition. In these cases, sample collection and geochemical analysis are often required to confidently identify mortar types and to confirm archaeological interpretations of the construction history of a given structure. Unfortunately, traditional analysis techniques are inherently destructive, and the collection of mortar samples, no matter how small, causes irreparable damage to the walls under study. A field-based, non-destructive protocol for the analysis of historic structures would improve archaeological interpretations without causing damage to fragile structures like those in Pompeii.
To this end, a project was undertaken the summer of 2008 using the FieldSpec3 spectroradiometer to conduct near-infrared reflectance spectroscopy of different mortar types in the House of the Vestals, an ancient elite house in Pompeii. The long wavelength range of the equipment's detectors, specifically ~2000nm-2300nm, was definitely useful for analyzing the lime component (CaCO3) of different mortars that varied in color. Results showed that the FieldSpec3 was able to clearly distinguish individual types of mortar, confirming the construction history of the House of the Vestals as determined by visual analysis. The FieldSpec3 allowed for rapid analysis of a larger sample set than would have been possible with traditional laboratory-based techniques. This technology may be utilized effectively in the future within structures built with several types of mortar that may not be so easily distinguished with visual analysis alone.