Obsidian is a volcanic glass whose formation is due to the rapid cooling of acid lavas (rich in silica), very viscous, generally of the rhyolithic type. This generates a hard, brittle material that fractures creating extremely sharp edges. The color of obsidian is generally black, but it can also present other colors (yellow, red, greenish brown) depending on the impurities present.

The name obsidian derives from a certain Obsius or Obsidius who, according to the Roman naturalist Pliny the Elder (1st century AD), discovered the rock during his trip to Ethiopia.

Obsidian is a relatively geologically unstable material.

It is rare to find pieces of obsidian older than 20 million years because, over time, obsidian tends to transform from volcanic glass to simple rock in a process known as "devitrification": in this phase the silicon molecules little by little they reorganize into a crystalline structure, making them lose their peculiar properties.

Where is it?

Obsidian deposits are found wherever there have been volcanic manifestations: United States, Mexico, Ecuador, Greece, Armenia, Turkey, New Zealand, Iceland, Kenya, Russia, Japan, Indonesia. In Italy, the main centers of obsidian extraction are those that have experienced rhyolithic volcanic eruptions (with a high silicon content) such as Lipari (Sicily), Pantelleria (Sicily) and the Massif of Monte Arci in the province of Oristano (Sardinia). Arci is the largest obsidian deposit in the entire Mediterranean Sea.


  • Chemical composition: Silicatic
  • Structure: amorphous
  • Texture: amorphous
  • Chemical formula: SiO 2
  • Hardness (Mohs): 5-5.5
  • Density: 2.3-2.65g / cm 3


Most of the obsidian is used to make rock wool, a sort of glass in very thin fibers obtained by melting it at 1300 ° C.

But obsidian is also used as an ornamental stone or as a gem and, thanks to the extremely sharp surfaces that can be obtained, of superior quality to steel, it is used to make scalpel blades for microsurgery and cardiac surgery.

Honed Black Obsidian


Among the American Indians obsidian was called "Apache's Tear" because, according to a legend, the tears shed by Apache women for their warriors who died in battle were transformed into drops of obsidian and whoever possessed a fragment would no longer cry.

The Greek historian Herodotus (V century BC), in the second book of Histories, reports that in Egypt the embalming specialists, before proceeding to the mummification of the bodies of the dead, extracted the entrails using a sharp Ethiopian stone. Obsidian is also mentioned by the philosopher Theophrastus, a pupil of Aristotle, who, in his geological treatise on rocks of the 4th century BC, mentions a black and dense rock from the island of Lipari. The first known use of obsidian as a cutting tool dates back to about 700,000 years ago, but to find an abundance of cutting artifacts it is necessary to move to Neolithic sites.

Many ancient peoples (Egyptians, Assyrians, Babylonians, Maya, Aztecs, Incas, etc.) used obsidian to make spearheads, arrowheads, mirrors, various cutting tools and ornamental objects.
Black Obsidian Pendant

Metaphysical angle

In the metaphysical world it is believed that obsidian is a protective stone and gives protection against negativity. It would absorb negative energies from the environment and help eliminate stress and mental tension.