**Antonia Moropoulou 1,\*, Ekaterini T. Delegou 1, Maria Apostolopoulou 1, Aikaterini Kolaiti 1, Christos Papatrechas 2, George Economou <sup>2</sup> and Constantinos Mavrogonatos <sup>3</sup>**


Received: 9 March 2019; Accepted: 23 April 2019; Published: 28 April 2019

**Abstract:** In this work, samples of the white marbles enclosing the Tomb of Christ, as well as samples from the interior marble facades of the Holy Aedicule structure surrounding the Tomb of Christ in the Church of Resurrection in Jerusalem, are investigated using petrographic and isotopic analysis. The aim is to characterize the marble samples and investigate their provenance. The results demonstrate that all examined marble samples originate from Proconnesos (Marmara island), and can be attributed to the so-called Proconnesos-1 variety. Published maximum grain size (MGS) and isotopic (δ18O and δ13C) values of Proconessos quarries are compared with the respective values displayed by the marble samples of the Holy Aedicule, aiming to achieve—to a certain degree—intra-site discriminations. A number of ancient quarries are excluded through this double parameter criterion as sources for the examined Holy Aedicule marbles. The discussion of petrographic and isotopic results in relation to historical testimonies and previously published archaeometry results, regarding the mortars of the Holy Aedicule, reveal that Proconnesos marble was the material of choice used at different construction phases of the Holy Aedicule, from the time of Constantine the Great and throughout the centuries, both for the cladding of the Holy Tomb and the interior facings of the Tomb Chamber and the Chapel of the Angel.

**Keywords:** Holy Sepulchre; Church of Resurrection; petrography; isotopic analysis; Proconnesos; cultural heritage; monument; history; archaeometry

### **1. Introduction**

Natural rocks have been used as a raw material for constructive and decorative purposes since antiquity. Many rock-types have been selected for these purposes, (e.g., chert, granite, gneiss, schists, serpentinite, etc.), but undoubtedly, marble has been the most prominent type [1], especially concerning monumental, religious and important buildings. Marbles are metamorphic rocks, consisting almost entirely of calcite, with minor admixture of a number of accessory minerals. In the broad Mediterranean region, marble mining activities have been documented since the Neolithic period, with constantly increasing rates of exploitation, which flourished during the Greco-Roman period [1].

White and colored marbles have been long known as a favorite building and decoration material of the ancient times. The provenance identification of the raw materials used during antiquity, is a matter of great significance to both historians and archaeologists [2], as well as to other scientists in the field of monument protection. This is not only because such results could lead towards understanding commercial and socio-economic relations (e.g., trade routes) among ancient populations, but because it could also provide the proper material for conservation and restoration interventions in damaged monuments and sculptures [3]. Especially for marbles, which were preferably used as raw material for sculpturing, building and decoration purposes, attempts to determine their provenance date back to the end of the 19th century. At that time, Lepsius (1890) [4], was the first who tried to use "scientific" criteria in order to define the provenance of marble-curved items, based mostly on their macroscopic characterization, an approach which later proved to be erroneous and/or inadequate. Since then, and especially during the last three decades, archaeometric studies have expanded significantly beyond macroscopic examination, by including new analytical techniques or combinations of more than one technique, in order to obtain more accurate results [2,3,5,6].

Petrographic investigation of rock samples is among the first truly scientific methods applied for provenance determination [7–10], because it is indicative of the environment of marble formation. This method comprises a number of parameters related to the mineralogy and the fabric of the rock. The mineralogical examination aims to identify the main and the accessory mineral phases that compose the rock. Beyond calcite and less commonly dolomite, which often exceed 95% of the rock volume, a number of accessory phases have been described for many marbles around the world [11]. In addition, the fabric of the studied sample gives significant information and may be critical in the identification of various rock types, as it reflects the degree of rock deformation, mostly expressed by the maximum grain size (MGS) and the grain boundary shape (GBS). These two parameters, coupled with the mineralogical content, provided encouraging results, but soon proved to be inadequate for a secure provenance determination. This is due to: (i) the great number of accessory minerals that were commonly identified; and (ii) the sometimes significant inhomogeneity of rock samples from the same quarry (e.g., differences in the dolomite content, grain size variations, etc.) [12].

Geochemical analyses, which focus on measuring minor (e.g., Na, Mn) and trace (e.g., REE) elements' concentrations, commonly conducted by neutron activation analysis (NAA) or inductively-coupled plasma mass spectrometry (ICP-MS) resulted in a number of significant geochemical data sets. Unfortunately, the inhomogeneous content of marbles in the aforementioned chemical impurities, as well as the overlapping of many data sets from different areas, again proved to be discouraging in relation to provenance determination.

Measuring the isotopic ratios of C and O in marble samples, was proposed by Craig and Craig, (1972) [13], and, since then, it is considered, along with petrographic analysis (and/or other analytical techniques), the most classic approach in archaeometry studies, especially for marble artifacts. This combination of methods commonly suffices and results in reliable data sets which allow scientists to make a relatively safe identification. Other analytical methods comprise cathodoluminescence, which is related to the impurities of Fe and Mn, electronic spin resonance and electronic paramagnetic resonance (ESR/EPR), as well as strontium isotopic measurements. Although the aforementioned methods usually provide additional information, they cannot be used alone, as they remain unreliable in attributing a marble artifact to its quarry of origin [12]. Moreover, the high cost of the Sr-isotopic measurements is often a reason for researchers to avoid this method. X-ray diffraction (XRD) and electron-probe micro-analysis (EPMA) are two methods commonly used to obtain mineral-chemical data, especially for accessory phases that could be used as pathfinders towards the provenance identification of the sample [11,14].

The last decades, the Association for the Study of Marbles and Other Stones in Antiquity (ASMOSIA) and its members have provided a very useful dataset and have proposed new methodological approaches for the provenance identification problem. Based mostly on isotopic and petrographic characterizations, a number of researchers have published detailed studies, especially for the most common marble types used in antiquity and have provided accurate datasets that compare artifact samples and geological material. These studies refer mainly to the Proconnesian (Marmara island) marble [15,16], the Thasian marble [17], the Carrara [18], the Parian marbles [19], the Aphrodisias marble [20] and the Pentelic marble [21–23].

Among the many marble-producing areas during the ancient times, some have proved to be major producers, due to the quality of their material and on account of their location on important trade routes or their vicinity to important ancient cities. In the case of white marbles, the most important quarrying locations around the Mediterranean are scattered mainly in what is now modern Greece, Turkey and Italy (Figure 1). The most important and frequently used white marbles since antiquity are the white marbles from Penteli, in Greece, from the Greek islands of Thasos and Paros, the Italian Carrara marble, as well as the Proconnesos marble from modern day Turkey.

**Figure 1.** Map of the eastern Mediterranean region indicating the locations of ancient quarrying sites, modified after Antonelli and Lazzarini 2015 [12]: (1) Candoglia; (2) Carrara; (3) Campiglia; (4) Doliana; (5) Mani; (6–7) Mts Pentelic and Hymettus; (8) Tinos; (9) Paros; (10) Naxos; (11) Kos; (12) Fourni; (13) Ikaria; (14) Samos; (15) Miletus; (16) Göktepe; (17) Aphrodisia; (18) Denizli; (19) Thiounta; (20) Docimium; (21) Sardis; (22) Ephesos; (23) Skyros; (24) Thasos; (25) Proconnesos (Marmara), indicated by red rectangular.

Pentelic marble is perhaps the most famous marble used in ancient monuments, due to its excellent quality; in classical Athens it was the material of choice, used for the construction of the Parthenon in Athens and the Hephaestus Temple in the Ancient Athenian Agora [13,24,25]. Its use was continuous throughout the ages, as it also adorns important neoclassical buildings of the 19th and 20th century in Athens [26].

Parian marble was used in various monuments in the ancient Greek and Roman world and was highly appreciated [27]. Owing to its high purity and texture, it was used in decorative elements, for example the decorative reliefs of the ancient Temple of Hephaestus in Athens, as well as important sculptures [28] and anthropomorphic sarcophagi [29]. Thasian marble was also widely used, in monuments (such as the burial monument of Amphipolis in Macedonia, Greece), as well as in Greek and Roman statues and reliefs [30]. Carrara marble has been used in monumental roman structures, such as the Pantheon and Trajan's column, roman sculptures, and sculptures of the Renaissance, such as Michalangelo's David, as well as in more recent monumental, religious and important buildings throughout the world [31–33].

The northern side of Proconnesos Island has been well known as a major marble producing area since the archaic period [34]. Its production spiked during the Roman times, around the second half of the first century AD, while the local quarries were made dependent on the imperial treasury by Hadrian. In the fourth century, the quarries produced ready-to-sculpt blocks and building elements, tied to the large imperial buildings of Constantine the Great [35]. Proconnesos marble, due to its appearance and quality, was a greatly appreciated marble. In addition, the insular nature of its quarries from which marble could be directly transported by sea, greatly reduced transportation costs, thus increasing its popularity [35]. In addition, the vicinity of the quarries to Constantinople, the capital city of the Byzantine empire, made the Proconnesian marble one of the most popular raw materials during the Byzantine times [16,36]. Proconnesian marble has been used in numerous monuments, sculptures and sarcophagus throughout the ages [37–41], as well as in important modern-day buildings.

A relatively recent study regarding the provenance of the marbles comprising the Sanctuary of the Great Gods in Samothrace presented a complex pattern of provenance including Thasian, Pentelic, Parian and Proconnesian marble, sometimes in combination [42]. This is true for many monuments, as reuse of older members from other monumental buildings is usual throughout all historical periods, an issue which complicates provenance studies.

The great importance of the above mentioned marble monuments, as well as the complexity of their construction and multiple construction/restoration phases, implies that accurate provenance identification is a very critical field of research; not only for restoration purposes, but also because it can broaden conceptions and interpretations in relation to historical and archaeological aspects regarding the selection, transportation and use—or even re-use—of this valuable material. In this framework, the provenance of marbles used in monumental buildings, such as the Holy Aedicule, is especially interesting and is herein addressed.

The Holy Aedicule is an indoor structure located in the center of the Rotunda area in the Church of Resurrection in Jerusalem (Figure 2a). It is the structure surrounding and containing what is believed to be the Tomb of Christ and is thus a religious site of great importance for the Christian World. The Holy Aedicule today consists of two chambers; the Chapel of the Angel to the east and the Holy Tomb Chamber to the west (Figure 2b). The exterior of the structure is covered with stone facings, consisting of locally quarried compact stones (mizzy and slayeb stones) (Figure 3) [43–45]. The interior of both chambers is adorned with marble facings, mostly of white coloration (Figure 4a, b). The Tomb of Christ, located at the northern side of the Tomb Chamber, is also enclosed within marble facing (Figure 4b).

**Figure 2.** (**a**) Ground plan of the Church of Resurrection in Jerusalem, indicating the location of the Holy Aedicule within the Rotunda area, modified after Lavvas 2009 [46]; (**b**) Section of the Holy Aedicule North view, indicating the basic parts of the structure, modified after Balodimos et al 2003 [47], Lavvas 2009 [46].

**Figure 3.** (**a**) View of the South façade of the Holy Aedicule as it is today; (**b**) The main entrance of the Holy Aedicule from the East, where the pilgrims enter.

**Figure 4.** (**a**) Interior west façade of the Chapel of the Angel, showing the low entrance to the Tomb Chamber, with the marble pedestal containing part of the stone of the Angel; (**b**) Tomb Chamber adorned with marble facings; the Holy Tomb is indicated on the right-hand side of the image.

In addition to its religious significance, it is also a site of high archaeological and architectural interest, as its evolution during the last 17 centuries reflects and embeds the tumultuous history of the city of Jerusalem. Since the fourth century AD, when the cave-hewn Tomb was uncovered by Saint Helena and Constantine the Great and enclosed within a structure (Aedicule), it has evolved into the complex structure that stands today, visited by millions of pilgrims annually [48]. The major historical events, constructions, destructions and subsequent reconstructions which mark the evolution of the Holy Aedicule structure are presented in Table 1.


**Table 1.** Major historical phases of the Holy Aedicule—Construction, Destructions and Restorations.


**Table 1.** *Cont*.

The rehabilitation project implemented under the scientific supervision of the National Technical University of Athens (NTUA), provided the framework to examine the building and decorative materials of the Holy Aedicule. It should be highlighted that on the 26th of October, 2016, the NTUA team was granted permission by the three Christian Communities—Guardians of the Holy Tomb, to open the Tomb of Christ during the grouting of the structure, in order to protect the burial surface. The top marble slab was thus shifted and the interior of the burial monument came to light; a lower marble plate, fragmented in a direction from west to east and in position to the north of the Tomb, was revealed; on the southern part of the Tomb, the burial rock, the original burial surface of the Tomb, was revealed [62,68].

The current study will try to identify the provenance of marble samples collected from the most holy site of Christianity, the Tomb of Christ, as well as from various locations of the Holy Aedicule enclosing it, by using mineralogical, petrographic and C-O isotopic analyses. The combination of these methods enables the marbles to be identified with an acceptable degree of reliability [3]. The obtained results are compared to relevant literature data in order to establish their provenance and an attempt for an intra-site topographical discrimination is made. These results are discussed in relation to historical sources and testimonies, as well as to previously published archaeometric results regarding the historical mortars of the Holy Aedicule [69]. Thus, new data regarding the evolution of the Aedicule, as well as information regarding the selection of marbles throughout the monument's history, emerges.
