A study by thermal treatment and X-ray powder diffraction on burnt fragmented bones from tombs II, IV and IX belonging to the hypogeic necropolis of “Sa Figu” near Ittiri, Sassari (Sardinia, Italy)

In the course of an anthropological investigation of three tombs of the hypogeic necropolis of “Sa Figu” (near the village of Ittiri in North Sardinia, Italy), numerous burnt bone fragments were collected. In particular, from the whole necropolis we selected a tenth of long bones from tomb IV, a small fragment of femur from tomb II and four fragments belonging to tomb IX. The aim of this work is to determine a temperature range to which the bone fragments were heated, in order to assess a funerary cremation which was presumably used at that time to quickly and hygienically eliminate the flashy parts of deceased people rather than a purification rite with fires inside the sepulchres. We attempted to evaluate the range of temperature to which the bones were likely subjected, making a joint use of thermal treatment and powder X-ray diffraction investigations. From our X-ray line broadening results carried out with a modern approach (Rietveld method), it emerged that a group of five fragmented burnt bones (one specimen belonging to tomb IV, the other four from tomb IX) were subjected to a heat treatment in a temperature range from 600 and 750 °C. Conversely another group of bones (belonging to tombs II and IV) turned out to be subjected to temperatures not higher than 250 °C.