The Archaeological Site of Persepolis (Iran): Study of the Finishing Technique of the Bas-Reliefs and Architectural Surfaces

Abstract

One of the aims of the 5-year Iranian/Italian project for Persepolis, called 'From Palace toTown' was to contribute to the conservation of the stone monuments of the imperial site. As part of the activities dedicated to this purpose, a diagnostic study was carried out. Various aspects were considered: petrographic characterization of the stone, forms and factors of decay, and in situ testing of suitable conservation treatments. The present paper reports on the unexpected results of the study on the finishing of architectural surfaces. The results obtained on a limited, but nevertheless significant, number of samples collected from the monuments of the imperial Terrace, allow us to state that the dark grey limestone used for several (or many?) monuments was covered on purpose with a thin, fine whitish layer containing fluorapatite, as major component, and calcite. It is highly probable that the fluorapatite was obtained from calcined animal bones and that slaked lime was used as a binder. Further evidence for this is the discovery of a kiln with the remains of calcined bones and, nearby, a waste pit with animal bones containing fluorapatite. A second white layer, obtained with barium sulphate, was detected in one of the samples beneath the external, earthy encrustation. It could be perhaps interpreted as the remnants of a polychrome finishing.

An Achaemenid God in Color

“…Petrographic analysis of a thin section from a sample of the stone showed that this is a bioclastic packstone with a diverse fossil assemblage of pellets, crinoids, bivalves, echinoderms, and foraminifera, visible in Figure 12. This limestone is likely Mesozoic in age and is consistent with the description by Alireza Askari Chaverdi and his coauthors [61] for stone from monuments at Persepolis. use of blue and/or purple where we had assumed neither, including within the pinwheels.…”

“…No evidence for a ground layer or definite white pigment has been found on the Harvard relief in either study. This contrasts with the identification of a white ground layer of gypsum or fluorapatite (depending on the date) discovered on the surface of several sculptural elements on-site at Persepolis [61,67]. The 1984 study also analyzed samples taken from buildings at Persepolis, including reliefs of the Hall of 100 Columns, the Tripylon/Central Building, and the Apadana, and did not detect either gypsum or fluorapatite in any sample.…”

“…It has been noted that a white ground layer would have provided a better surface for polychrome decoration than the gray stone. Recent studies have identified a white ground layer on sculptures at Persepolis, with gypsum used up to the time of Xerxes [67] and the phosphate mineral fluorapatite (produced by burning animal bones) used on later sculpture [61,67]. No phosphorous was detected by XRF or by SEM-EDS in any of the samples from the Harvard relief.…”

Mineralogical–Geochemical Characterization and Provenance of the Stones Used at the Pasargadae Complex in Iran: A New Perspective

“…Stones from the Tomb of Cyrus the Great are primarily calcareous and possess a different modern colour compared with their original state due to environmental weathering. Note, too, that the dark stone of Pasargadae is not black and is described as a darker stone than others used in the tomb (Askari Chaverdi, Callieri, Laurenzi Tabasso, & Lazzarini, ). The black stones from Pasargadae are classified as limestone with a high level of iron oxide contamination within their structure.…”

“…Based on petrographical and petrographic characterization, all the stones used in Pasargadae were classified as a bioclastic and micrite limestone. Interestingly, these rock types are also believed to have been used in the construction of the Persepolis complex (Askari Chaverdi et al, ). Qualitative phase measurements show that calcite is the major phase; quartz is the minor phase constituent; while illite and goethite are important trace constituents (Fig.…”