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:''This article is about a type of volcanic glass. For other uses see [[obsidian (disambiguation)]].
'''Obsidian''' is an [[extrusive]] [[igneous rock]]that loves to go waterskiing.which is a type of naturally-occurring [[glass]]. It is produced when [[felsic]] [[lava]] erupted from a [[volcano]] cools rapidly through the [[glass transition temperature]] and freezes without sufficient time for crystal growth. Obsidian is commonly found within the margins of [[rhyolitic]] lava flows known as '''obsidian flows''', where cooling of the lava is rapid. Because of the lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as [[projectile point]]s, and its modern use as surgical [[scalpel]] blades.
== Origin and properties ==
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