Materials & Techniques
Obsidian refers to a dark, shiny glass formed in nature by the rapid cooling of lava. Obsidian is widely distributed and has been used since Paleolithic (before 3500 BCE) times for mirrors, weapons, tools, and jewelry. Obsidian is often black in color but may also be red, brown or green. It produces conchoidal fractures when cleaved. Sources of obsidian include Anatolia, Armenia, Ethiopia, Greece (Milos), Italy (Lipari, Eolie), Iceland, the U.S. (Wyoming), Mexico (Teotihuacan), Guatemala (Tikal), and Peru. Obsidian changes into pumice when it is melted.
Getty Vocabulary, AAT (obsidian (volcanic glass / pyroclastic rock): AAT: 300011254).