Obsidian is created naturally from rapid cooling volcanic lava. And is sometimes called volcanic glass because it is created by rapidly cooling molten lava. The lava contains a high content of silica sand, about 80 percent, and glass is produced naturally. Obsidian can be found in many different colors with many different occlusions that give each piece a unique signature. The most common color is black. However, the color is influenced by what elements the molten lava came into contact with while cooling.
Ancient people discovered that flakes of obsidian are very sharp and can be shaped. The first arrow heads, spear points and scraping tools were created from obsidian. Even today some very sharp a specialized medical scalpels use obsidian.