Interactive workshop to learn about obsidian, the rare natural glass of volcanic origin, present in Sardinia in Monte Arci. Its chemical composition, physical structure and fracture method make it a unique stone, of extraordinary interest in the varied panorama of rocks that characterize the geological formations of our island. An interest that was also shown by the ancient communities that inhabited Sardinia in the Neolithic period, who used obsidian to create diversified tools, useful for daily life, managing to organize a system of collection and exploitation of the material which involved distant lands, located beyond the sea, up to distant Catalonia. The activity involves the analysis of the raw material, knowledge of chipping techniques and individual experimentation with the use of obsidian as a cutting stone.