Deposit of obsidian “Conca ‘e Cannas”
This area in Monte Arci’s southern front, located between two tight valleys that meet in Riu Cannas, has great importance both on a scenery point of view as numerous crags, in continuity with the rocks in the area of Su Columbariu, have the same characteristic tafonic feature in the rock, and historical-cultural point of view,as this area provides the biggest and the best quality deposit of obsidian within the Mediterranean basin.
The last volcanic activity to rise to the surface of the volcano Arci (from 3 to 1,8 millions of years ago) produced the obsidian, this was enabled by the rapid cooling of the magma upon its release through the Earth’s crust. This natural volcanic glass can be found mainly in black colour, but it is possible to find in in different variants, even the rare “snowflake” obsidian.
The obsidian was used by prehistoric men, starting from the late to middle Neolithic (6/8.000 years ago), thanks to its peculiar features (such as hardness and fracture with sharp surfaces), for the production of daily objects such as knives, scrapers, darts, spearheads, etc. Due to the importance this resource had for the Neolithic inhabitants, Giovanni Lilliu defined it “the black gold of antiquity”.
For centuries, Conca ‘e Cannas’ obsidian was exported, both in nodules and molded, towards Corsica, the north of the Italian peninsula, south of the France and Catalonia.
This deposit was discovered in 1953 by the academic Cornelio Puxeddu, who dedicated most of his studies to Monte Arci’s territory. In 1956, he participated in a territorial survey with professor Giovanni Lilliu, where he had the opportunity to verify the relevance ad size of the existing deposit of this precious volcanic glass.
Conca ‘e Cannas obsidian is located in situ in a perlite matrix, and for this reason in the second half of the twentieth century, a quarry was opened to enable extraction of this material which is now widely used in construction for thermal and acoustic insulation.