Geological references
- U.S. Geological SurveyVolcano Watch — Obsidian, a scarce commodity in Hawaiʻi. Formation, composition, color, banding, conchoidal fracture, and devitrification.
- U.S. Geological Survey, Yellowstone Volcano ObservatoryYellowstone’s tool-making lava flows. Silica-rich rhyolite, crystal-poor glass, fracture, and toolstone.
- U.S. National Park ServiceObsidian: The MVP of Yellowstone’s “Stones”. Glass structure, fracture, archaeology, and responsible interpretation.
- U.S. National Park Service, Bandelier National MonumentObsidian. Rapid cooling, dark glassy appearance, sharp edges, and cultural use.
- U.S. Geological SurveyVolcanoes of the United States: basaltic volcanism. Basaltic magma, fluidity, lava flows, and shield volcanoes.
Image credits
- Obsidian from Panum CraterPhotograph by Carrie Wallestad, via Wikimedia Commons. CC BY-SA 4.0. Resized for web display.
- Polished snowflake obsidianPhotograph by Bordercolliez, via Wikimedia Commons. CC0 1.0 public-domain dedication. Resized for web display.
- Ancient obsidian arrowhead, Big Valley, CaliforniaPhotograph by Darron Birgenheier, via Wikimedia Commons. CC BY-SA 2.0. Resized for web display. The site does not independently verify the object’s stated provenance.
- Obsidian talus at Obsidian DomePhotograph by Mark A. Wilson, via Wikimedia Commons. Released into the public domain.
- Basalt from Mount Zion Church BasaltPhotograph by Boomersooner6553, via Wikimedia Commons. CC0 1.0 public-domain dedication. Resized for web display.
- Glass Mountain, Medicine Lake VolcanoUSGS photograph by Julie Donnelly-Nolan, via Wikimedia Commons. U.S. federal government work, public domain.
- Obsidian arrowhead faviconU.S. Department of Energy image, via Wikimedia Commons. Public domain in the United States.
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