Written by Giannis Grammatikakis
(http://dx.doi.org/10.1016/j.jasrep.2017.09.029)
Serpentinites have been widely used as a raw material in a huge variety of shapes during the Minoan period, mainly for the construction of artifacts both for domestic use as well as religious purposes. According to Warren (1969), almost half of the entire corpus of the Minoan stone vases is consisted of objects made out of serpentinite. However, the utilization of serpentinites is extremely limited in the Minoan palatial architecture. In all the cases where the use of serpentinite is documented in the palace of Knossos, it has been used for the construction of column bases. The aim of this study is to look into the material used for the construction of the drain located under the stair leading to the adyton (sanctuary) of the “House of the High Priest”, one of the peripheral monuments of the Palace of Knossos (fig.1). Despite the fact that Sir A. Evans documented the stone drain and described the raw material as stone, no further comments were made regarding the exact type of stone used by the Minoans. Furthermore, the fact that a rather unusual material was used for the construction of a drain, instead of a more typical material such as limestone or sandstone, enhances the ill-defined and controversial character of the “House of the High Priest”.

Fig. 1. The part of the ancient drain exposed during the restoration works

The initial mineralogical characterization of the drain material, was carried out by means of X-ray powder Diffraction leading to the identification of several minerals and polymorphs. Further examination of the sample in terms of microstructural and chemical analysis of the different inclusions, was implemented by means of confocal μ-Raman spectroscopy.
Within the concept of this study, emphasis is given to the application of this nondestructive and noninvasive technique that can be applied in situ for the analysis and characterization of objects of archaeological significance made out of serpentinite minerals, where often sample acquisition is not possible.
In this study several Raman spectra were acquired from the sample of the ancient drain. In the Raman spectra shown in Fig. 2, the presence of chrysotile, calcite and steatite is documented. In Spectrum 1 the two Raman spectra the presence of chrysotile one of the serpentine family of minerals is indicated by the presence of the Raman bands at 232, 348, 391, 622 και 690 cm−1.

Fig. 2. Two Raman spectra of chrysotile obtained for two different spots from the sample of the High Priests House drain near Knossos.

In many cases the morphological values of an archaeological object consist of the most important aspects that have to be preserved. In such cases, extensive and systematic sampling, or even the acquisition of a small fragment are out of the question. It has been demonstrated here, as well as in many relevant papers, that Raman spectroscopy can provide valid information that can be used for the characterization of minerals.
The choice of Raman spectroscopy as the main non-destructive analytical tool consists a strategic decision for two main reasons: (a) There are several other architectural elements implemented in the Minoan palatial architecture allegedly made out of serpentinite that macroscopically bear different characteristics and have to be examined, and (b) the majority of the Minoan stone vases corpus is consisted of artifacts made out of serpentinite but in both cases sampling is not possible. Lastly, the correlation of the data acquired from the analysis of the serpentinite outcrops on the island of Crete, with those from the archaeological objects might augment the development of knowledge regarding the cultural networks among the agricultural areas, where the serpentinite sources are located towards the centers of the Minoan civilization.
Within the context of this study, it is of minor importance whether the ‘adyton’ of the “House of the High Priest” is a sacred site or not, since the use of serpentinites for the construction of architectural elements, is particularly out of the ordinary in the neopalatial period. In previous periods serpentinite containing rocks were used due to their aesthetic values (PM I·II, 213). Nevertheless in the case of the “House of the High Priest”, the fact that the drain was “hidden” increases the chances that this material was used because of its properties (imaginary or real) and not for its appearance.
Evans, A., 1964. The Palace of Minos at Knossos, I, II, III, IV, New York. (pp. Ι, 141–3, 213, 225–30, 327, 334–5, 363, 378–80, 393–6, 400, ΙΙ, 161, ΙΙΙ, 5, 236–44, 245-59, 492).
Warren, P., 1965. Two Stone Vases From Knossos, BSA. 60. pp. 248–315.
Giannis Grammatikakis is a conservation scientist with an MSc in environmental chemistry and a PhD in inorganic chemistry.
In 2005 he started his career working as “field” conservator, on monuments, as a member of the conservation team of Parthenon Temple on the Acropolis of Athens. Since 2006 as an employee of 23rd
E.P.C.A. (Hellenic Ministry of Culture) he has made several surveys and restoration studies for several monuments mostly from the Minoan period. From 2010 till the end of the project in 2014, he was the Head conservator for the peripheral monuments of the Palace of Knossos.
Currently he is working as a researcher in the department of chemistry, University of Crete. He is also a member of the The Heritage Management Organization and the owner of Archaeoanalysis DBA.