Modern archaeologists have developed a dating system to calculate the age of obsidian artifacts depending from the content of water in the object. Obsidian cores (unworked lumps) and blades were traded great distances inland from the coast. Obsidian can be identified in Greece as coming from different islands in the Aegean Sea. So archaeologists can trace the origins of a particular artifact. Each volcano and in some cases each volcanic eruption produces a distinguishable type of obsidian.

Native American people traded obsidian throughout North America. Called a macuahuitl, the weapon could cause terrible injuries, because it combined the sharp cutting edge of an obsidian blade with the ragged cut of a serrated edge. Mesoamericans also made a type of sword with obsidian blades mounted in a wooden body. It was also polished to create early mirrors. It was worked for tools and decorative objects. Pre-Columbian Mesoamericans' used obsidian often. Obsidian was valued in Stone Age cultures because, like flint, it could be chipped to produce hand axes, sharp blades or arrowheads. It may contain patterns of gas which produce effects such as a golden sheen ( sheen obsidian) or a rainbow sheen ( rainbow obsidian). In some stones, small crystals produce a snowflake pattern ( snowflake obsidian). Iron and magnesium typically give the obsidian a dark green to brown to black color. Usually dark, the color varies on the presence of different materials. Obsidian has little water, but takes it in if it sits in groundwater. It breaks down faster when water is present. So, no obsidian is older than Cretaceous age. Over time, the glass becomes fine-grained crystals. It is metastable: it changes very slowly. It consists mainly of SiO 2 ( silicon dioxide), usually 70% or more. Obsidian is mineral-like, but not crystalline.

Obsidian definition color