Obsidian

Obsidian is a type of volcanic glass, a rock formed as a result of magmatic activity, where the hot, acidic and viscous lava comes into contact with the cold environment and then quickly becomes stiff. The rock is very rich in SiO2 compounds and is a natural form of glass.
From the Palaeolithic and Neolithic, the obsidian was used to produce tools, mostly scrapers, spearguns or knives. The oldest archaeological find that demonstrates the use of obsidian falls into Mesopotamia about 9,000 years ago. In South America, it was used by the Indian tribes to protect them from evil forces, and to preserve processed items made from obsidian. They are attributed to this day by magical properties or therapeutic effects, but their occurrence has never been scientifically proven. With the development of metal processing, obsidian began to lose importance and began to use it as a decorative or ornamental stone in jewelery.