igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, typically black to dark brown in color, vitreous luster, amorphous crystal structure with distinct conchoidal fracture.
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Physical properties
Hardness of 5 to 5.5 on the Mohs scale, typically black to dark brown in color, vitreous luster, amorphous crystal structure with distinct conchoidal fracture.
Formation & geological history
Formed as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth.
Uses & applications
Used historically for sharp tools and weapons like arrowheads, and currently in decorative jewelry and surgical scalpel blades.
Geological facts
Despite appearing black, obsidian is composed mostly of silica and is actually transparent in thin flakes.
Field identification & locations
Easily identified by its glassy texture and razor-sharp conchoidal fracture edges; found worldwide in areas with recent volcanic activity.
