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Most of Roman archaeological sites in Morocco contain many mosaics, it offers significant pavements decorated with the majority of architectural buildings components different archaeological sites of Morocco. Petrographic and mineralogical analyses of tesserae coming from some of Roman mosaics in Volubilis, and Lixus, archaeological sites have revealed the petrographic nature of the rocks used in the decoration of different tessellata. The knowledge of petrographical characteristics of these tesserae represents an essential step to understand mechanical properties of the used materials, their weathering processes and the location of their origin. This comparative study carried on natural materials used in roman mosaics tesselata in some archaeological sites give us ideas about the provenance of building materials and the movement of materials in Morocco and in the Mediterranean region. This study will also provide solutions to guide professionals in the choice of interventions related to the restoration and conservation.

Roman mosaics in Volubilis are opus tessellatum type. They show different deterioration features represented by the lacunae formation (lack of tesserae) and break down of mosaic pavements by fracturing. The deterioration of the tessellatum and the formation of cracks are related to the swelling of soil supporting these mosaics. Furthermore, the tessellatum is also damaged by chemical dissolution of the fine grained-mortar between (lime and quartz fine grain) and under tesserae, giving an important porosity and making the tessellatum very easy to collapse. A part from limestone tesserae, which show formation of vesicles by chemical dissolution, other ones such as marble and glass tesserae appear to be resistant to the weathering action.