igneous
Obsidian
Volcanic Glass
AI-generated identification · may be incorrectHardness 5 to 5.5 on the Mohs scale, typically black to dark brown with a vitreous luster and distinct conchoidal fracture.
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Physical properties
Hardness 5 to 5.5 on the Mohs scale, typically black to dark brown with a vitreous luster and distinct conchoidal fracture.
Formation & geological history
Formed as extrusive igneous rock from rapidly cooling felsic lava, preventing crystal growth.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in decorative objects and jewelry.
Geological facts
Obsidian fractures with extremely sharp edges, sometimes sharper than surgical steel scalpels.
Field identification & locations
Identified by its glassy appearance, conchoidal fracture, and lack of visible crystal structure.
