igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness 5 to 5.5 on Mohs scale, typically black or dark brown, vitreous luster, conchoidal fracture, amorphous crystal structure.
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Physical properties
Hardness 5 to 5.5 on Mohs scale, typically black or dark brown, vitreous luster, conchoidal fracture, amorphous crystal structure.
Formation & geological history
Formed from rapidly cooling felsic lava extruded from volcanic vents, lacking time for crystal growth.
Uses & applications
Used historically for cutting tools and arrowheads, and currently in decorative jewelry and surgical scalpel blades.
Geological facts
Despite its dark color, obsidian is chemically similar to light-colored felsic rocks like rhyolite and granite.
Field identification & locations
Easily identified by its glass-like appearance and extremely sharp conchoidal fracture edges; found in volcanic regions worldwide.
