Mining Exploration, Raw Materials and Production Technologies of Mortars in the Different Civilization Periods in Menorca Island (Spain)

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.