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Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled.These bubbles can produce interesting effects such as a golden sheen (sheen obsidian).This is the case in Yaxchilán, a Maya city where even warfare implications have been studied linked with obsidian use and its debris.Pre-Columbian Mesoamericans' use of obsidian was extensive and sophisticated; including carved and worked obsidian for tools and decorative objects.Obsidian flows which may be hiked on are found within the calderas of Newberry Volcano and Medicine Lake Volcano in the Cascade Range of western North America, and at Inyo Craters east of the Sierra Nevada in California. states of Virginia, as well as Pennsylvania and North Carolina.Yellowstone National Park has a mountainside containing obsidian located between Mammoth Hot Springs and the Norris Geyser Basin, and deposits can be found in many other western U. states including Arizona, Colorado, New Mexico, Texas, Utah, Washington, and Idaho. There are only four major deposit areas in the central Mediterranean: Lipari, Pantelleria, Palmarola and Monte Arci.
It presents a different appearance depending on how it is cut: in one direction it is jet black, while in another it is glistening gray.
Eight obsidian artifacts dating to the Chalcolithic Age found at this site were traced to obsidian sources in Anatolia.
Neutron activation analysis (NAA) on the obsidian found at this site helped to reveal trade routes and exchange networks previously unknown.
It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) induces a high viscosity and polymerization degree of the lava.
An iridescent, rainbow-like sheen (rainbow obsidian) is caused by inclusions of magnetite nanoparticles.