Obsidian is one of the main indicators of prehistoric archeology, a volcanic glass highly sought after in the Mediterranean basin thanks to its many qualities. According to the testimony of Pliny the Elder (XNUMXst century BC), this natural glass owes its name to the Roman merchant and explorer Obsius or Obsidius, who discovered it in Ethiopia.
Geology notes
Obsidian belongs to the category of extrusive igneous rocks: product of the rapid cooling of the lava flow, rich in silica. The rapidity of cooling precludes the ordered formation of a crystalline lattice. The atoms assume a chaotic, amorphous arrangement, as in a superviscous liquid.
Obsidian is therefore presented as a natural glass, completely similar to that produced by man.
The qualities of obsidian
This volcanic glass was highly sought after by ancient peoples, who appreciated two qualities: its brightness (on a predominantly black colour, but also green, blue and red, depending on the types of oxides present), which made it a perfect material for jewelry making; and a tendency to break with a smooth, curved structure, resulting in extremely sharp edges, useful for making blades and weapon points.
An indicator of the trade routes of the ancient world
The extraction of obsidian spread to numerous regions, subject to volcanic eruptions rhyolitic, i.e. with a high silicon content. And the Mediterranean it became one of the nerve centers for its trade, thanks to the presence of deposits in places such as Lipari and Pantelleria in Sicily and the massif of Monte Acri in Sardinia.
Starting from 6000 BC, obsidian was extracted in blocks from lava flows and treated to make arrowheads and spears, knives and scrapers for working leather.
From a bargaining chip so coveted as to earn the nickname of “prehistoric black gold”, obsidian was replaced, around 5000 BC, by metals. However, this figure does not diminish the charm of a material with a millenary tradition, capable of affecting theevolution of the main ancient civilizations, from the Mesopotamian ones to the Egyptian one, up to the American pre-Hispanic ones. The study of obsidian fragments, attributable to specific volcanoes or deposits, has also favored the reconstruction of ancient trade routes, showing us a truly surprising trading network for the time. Consider, in fact, that a Chilean obsidian from the Chaitén volcano it was found more than 400 km away from its original deposit.
Applications in modernity
Currently obsidian is used to make the Rock wool, an amorphous silicate used as an insulating material in the construction, industrial and naval sectors.
Furthermore, the charm of the black gold of Prehistory is still alive in the making of jewelry, vases, statues and other decorative items.
And, in the scientific field, obsidian is ideal for applications where a particularly fine cutting action is required. This volcanic glass was used as a scalpel blade, thanks to its sharper cutting edge and more regular surface than the corresponding metal instrumentation. Furthermore, according to some studies, the incisions made with obsidian favor a faster healing of the tissues and prevent allergic forms, due to the metallic traces present in the steel blades.
However, a major limitation to their use is given by their fragility: obsidian blades do not adequately tolerate lateral pressure and are therefore more prone to dangerous breakage. Lastly, the costs are added to this problem, which are decidedly higher than metal blades. For these reasons, the use of obsidian instruments is limited today to the field of surgery on research animals.
Sources: geopop.it, ilmeteo.net, wikipedia, vitantica.net
