Where is Obsidian in Rhyolite found?
Volcanic glass (Obsidian) within a fine-grained felsic volcanic rock (Rhyolite)
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Open the appObsidian in Rhyolite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Obsidian in Rhyolite
Newberry Volcano, Oregon, USA
Known for extensive rhyolitic lava flows and obsidian deposits, including areas where obsidian is intermixed with rhyolite.
Glass Mountain, California, USA
Part of the Long Valley Caldera, this area features rhyolitic domes and flows with significant obsidian occurrences.
Yellowstone National Park, Wyoming, USA
The Yellowstone Caldera region contains numerous rhyolitic formations and obsidian flows.
Lipari Islands, Italy
Volcanic islands with rhyolitic activity and historical obsidian sources.
Mexico (e.g., Sierra de las Navajas)
Historically significant obsidian sources often associated with rhyolitic volcanism.
Collecting tips
- Look for Volcanic Regions. Focus your search on areas with recent or geologically young felsic volcanic activity, particularly those known for rhyolite domes, flows, or caldera structures.
- Examine Outcrop Margins. Obsidian often forms at the quenched margins of rhyolitic lava flows or domes. Look for transitions from crystalline rhyolite to glassy textures.
- Identify Flow Banding. Rhyolite frequently exhibits flow banding, which can sometimes delineate areas where obsidian lenses or layers are present due to differential flow and cooling.
- Check for Conchoidal Fracture. The glassy, sharp-edged conchoidal fracture of obsidian is a key indicator when distinguishing it from the more granular or dull fracture of rhyolite.
- Safety Precautions. Obsidian can produce extremely sharp edges. Handle specimens with care to avoid cuts. Always wear appropriate safety gear, including gloves and eye protection, when collecting in volcanic areas. Be aware of unstable terrain and potential hazards in volcanic environments.
Quick Check
- Color:
- Obsidian: Dark (black, brown, green); Rhyolite: Light (pink, gray, white)
- Luster:
- Obsidian: Vitreous; Rhyolite: Dull to earthy
- Streak:
- White (for both, though obsidian is typically too hard to streak on unglazed porcelain)
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