'''Obsidian''' is a black, glass-like [[Igneous rock|igneous]] [[rock]] that forms when [[lava]] cools quickly. Broken rocks have sharp edges. Ancients used it for blades in [[knives]] and [[tools]].
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'''Obsidian''' is a black, glass-like [[Igneous_rock|igneous]] [[rock]] that forms when [[lava]] cools quickly. Broken rocks have sharp edges. Ancients used it for blades in [[knives]] and [[tools]].