Origin, Properties, and Occurrence of Obsidian
- Obsidian is a volcanic glass formed when lava cools rapidly with minimal crystal growth.
- It is produced from felsic lava rich in elements like silicon, oxygen, aluminium, sodium, and potassium.
- Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows.
- It has a high viscosity due to its high silica content, inhibiting the formation of mineral crystals.
- Obsidian is hard, brittle, and amorphous, resulting in sharp edges when it fractures.
- Obsidian is found near volcanoes in locations that have undergone rhyolitic eruptions.
- It can be found in various countries including Argentina, Australia, Italy, Japan, Mexico, Russia, Turkey, and the United States.
- Obsidian flows can be hiked on in locations such as Newberry Volcano and Medicine Lake Volcano in the Cascade Range.
- Yellowstone National Park in the U.S. has a mountainside containing obsidian.
- Major deposit areas in the central Mediterranean include Lipari, Pantelleria, Palmarola, and Monte Arci.
Prehistoric and Historical Use of Obsidian
- Obsidian artifacts have been found dating back to the Acheulian age, around 700,000 BC.
- It was used for making bladelets, which were traded in regions like Sicily, Croatia, and the Po river valley.
- Obsidian bladelets were used in rituals such as circumcisions and cutting umbilical cords.
- Anatolian sources of obsidian were used in the Levant and Iraqi Kurdistan from around 12,500 BC.
- Obsidian artifacts are common in early Mesopotamian urban centers like Tell Brak.
- Obsidian artifacts appeared in Central Europe during the Middle Paleolithic and became common in the Upper Paleolithic.
- It played a role in the transmission of Neolithic knowledge and was used for chipped tools.
- The island of Milos was a source of obsidian for cultures around Greece.
- The Starčevo–Körös–Criș culture obtained obsidian from sources in Hungary and Slovakia.
- The Cardium-Impresso cultural complex acquired obsidian from the central Mediterranean.
Obsidian in Different Regions
- Obsidian blades manufactured in the Ubaid civilization in 5th millennium BC Turkey.
- Ancient Egyptians imported obsidian from the eastern Mediterranean and southern Red Sea regions.
- Obsidian tools were used in Japan near volcanic areas during the Jōmon period.
- Obsidian artifacts found in Gilat, Israel traced back to Anatolia, revealing trade routes.
- Neutron activation analysis helped uncover previously unknown trade networks.
- Obsidian analysis helps understand Mesoamerican commerce, production, and distribution.
- Chumash sites in California show evidence of trade with Casa Diablo Hot Springs.
- Mesoamericans used obsidian for tools, decorative objects, and weapons like macuahuitl.
- Aztec priests used obsidian mirrors for divination linked to Tezcatlipoca, god of obsidian.
- Lapita culture in the Pacific Ocean used obsidian tools and engaged in long-distance trading.
- Rapa Nui (Easter Island) used obsidian for edged tools and in the eyes of Moai statues.
- Rongorongo glyphs on Easter Island were inscribed on obsidian.
- Obsidian tools associated with prestige or high status in the Lapita culture.
- Obsidian trade played a role in economic and social aspects of Oceania civilizations.
Characteristics of Obsidian
- Obsidian is not a true mineral because it is a glass and lacks crystalline structure.
- Its composition is variable, making it sometimes classified as a mineraloid.
- Pure obsidian is usually dark in appearance, but impurities can give it colors ranging from brown to black.
- Inclusions of magnetite can create patterns like snowflake obsidian or sheen obsidian.
- Rainbow obsidian contains oriented nanorods of hedenbergite, producing rainbow striping effects.
Modern Uses and Other Related Concepts
- Obsidian can be used to make extremely sharp knives and surgical scalpels.
- Obsidian blades can have a cutting edge sharper than high-quality steel scalpels.
- Obsidian incisions in rats showed fewer inflammatory cells and less granulation tissue.
- Obsidian scalpels are used for surgical research on animals.
- Obsidian is also used for ornamental purposes and as a gemstone.
- Apache tears, helenite, and hyaloclastite are related to obsidian.
- Knapping is the technique used to shape obsidian into stone tools.
- Libyan desert glass is a type of desert glass similar to obsidian.
- Mayor Island in New Zealand is a source of Māori obsidian tools.
- Obsidian hydration dating is a geochemical dating method used with obsidian artifacts.
Obsidian Data Sources