Abstract
This study deals with the mortars and subordinately rocks collected from the archaeological site of Cap de Forma, that is a “Bien de Interés Cultural” located on a cape along the southeastern coast of Menorca (Balearic Islands, Spain). Cap de Forma consists of different structures belonging to different periods and civilization phases: a fortified settlement of Talaiotic age, built in cyclopean technique and including three rooms and a rainwater cistern; a nearby necropolis of tombs (cuevas) excavated into the cliff; a more recent site occupancy testified by plastering of the cistern; a house-fort (pecheña casa-quartel), a lookout point of the 17th–18th century. Compositional features and mineralogy of mortars and rocks were investigated by optical microscopy and X-ray diffraction. Physical properties (density, porosity, water saturation and water saturation coefficients and mechanical strength) were also determined. This work is aimed at characterizing these archaeologic remains to understand the building technique, the choice of raw materials and possibly their provenance, taking into account the age and civilization they belong to. Results indicate that cocciopesto-rich mortars were used in the cistern watertight and other ancient structures linking from a Roman age. The cocciopesto seems to derive from local pottery even if some evidence would suggest the contrary, whereas the source of the binder is definitely the local Mg-rich limestone. The house-fort was plastered with gypsum-based mortars in the 17th–18th century. The most likely source of raw gypsum was the island of Mallorca where some quarries were opened in the same period. Mechanical and physical tests reveal a strong state of decay that requires conservation actions. This work sheds light on a poorly studied monument, better constraining the different phases of its occupation. Some interesting questions, such as the cocciopesto provenance, are still open.
Highlights
Data of the compositional characteristics of mortars and stones sampled from the archaeological complex of Cap de Forma are shown in Table 2, which summarizes the results of macroscopic and mesoscopic analyses under reflected light microscope (RLOM), the microscopic analyses in polarized light (PL-optical microscopy (OM)) and the diffractometric ones on powdered samples (XRD; Figure 5)
On the basis of the composition of the aggregate used in mixing with the binder, On the basis of the composition the aggregate used in mixing with the binder, four four main populations of mortars are of distinguished: main1.populations mortars are cocciopestoof mortars from thedistinguished: pit with a subordinate fraction of sil‐
This different composition is due to the fact that the two types of mortars belong to different historical contexts: the mortar of group H belongs to the 17th–18th century AD
Summary
On the one hand, high-value and/or rare materials were imported even from far source regions if not available on site (see for instance [16,17]), on the other hand low-value materials were mainly provided from local or nearby sources (as in the cases of [3,18,19]). The supply of geomaterials from local outcrops was not always so easy, as the territory sometimes did not offer suitable materials for the work to be carried out. In the case of aggregates for mortars, the lack of high-quality materials, close to the building sites, forced the builders to make a choice between the use of the local low-quality materials (more economic) or the supply from a wider area (more functional) [19]. The aggregates’ provision implied the quarrying from rocky outcrops, as well as from sedimentary deposits located in various environment-depositional contexts, such as river or beach deposits [19,20,21]
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