Obsidian is a volcanic glass whose formation is due to the very rapid cooling of lava, always rich in silicate ions (from 40% to over 65%), which are unable to achieve the ordered formation of a crystalline lattice, but assume a chaotic arrangement (amorphous structure) as in a superviscous liquid. Obsidian is a natural glass, completely similar to that of human production.
A highly sought-after raw material in ancient times for the manufacture of cutting tools (mainly knives), it was one of the goods that animated Mediterranean trade and supported the economic life of the places of extraction, such as Sardinia, Lipari or Pantelleria, in the prehistoric period. Today it is still worked into small decorative objects, jewelry, scalpel blades.
Pliny called it lapis obsianus or obsidianus in honor of a certain Obsius or Obsidius, who first mentioned the stone in some areas of Ethiopia. Some findings suggest that the stone was known in ancient times: the Nuragic civilization used it mainly to build spears and arrows and tools of various types, the ancient Egyptians used obsidian to make scarabs and seals while in Central America it was used by pre-Columbian civilizations.