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Wikipedia: Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools without 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.
![[Obsidian debris (talus), Obsidian Dome, California.]](http://images.ookaboo.com/photo/s/ObsidianDomeCA_s.jpg "Obsidian debris (talus), Obsidian Dome, California.")
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![[Pig carved in snowflake obsidian, 10 centimeters long]](http://images.ookaboo.com/photo/s/Pig_snowobsidian_s.jpg "Pig carved in snowflake obsidian, 10 centimeters long")
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 from Wilson44691 |
UNKNOWN LICENSE from Arpingstone
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![[Pile of obsidian on Newberry Obsidian flow, central Oregon]](http://images.ookaboo.com/photo/s/NewberryObsidianPile_s.jpg "Pile of obsidian on Newberry Obsidian flow, central Oregon")
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![[Rainbow obsidian]](http://images.ookaboo.com/photo/s/Rainbow_obsidian_s.jpg "Rainbow obsidian")
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 from Exsuscito |
from Mila Zinkova |
![[Glass Mountain, a large obsidian flow at Medicine Lake Volcano]](http://images.ookaboo.com/photo/s/Glass_Mountain_on_Medicine_Lake_Volcano_750px_s.jpg "Glass Mountain, a large obsidian flow at Medicine Lake Volcano")
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 from :en:user:maveric149 |
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