igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness 5-5.5 on Mohs scale, dark black or dark brown color, vitreous luster, amorphous crystal structure, conchoidal fracture.
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Physical properties
Hardness 5-5.5 on Mohs scale, dark black or dark brown color, vitreous luster, amorphous crystal structure, conchoidal fracture.
Formation & geological history
Formed rapidly from cooling felsic lava extruded from a volcano with little crystal growth.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in jewelry and decorative objects.
Geological facts
Despite looking like a rock, obsidian is a mineraloid because it lacks a crystalline structure.
Field identification & locations
Easily identified by its glass-like appearance, smooth curved fracture surfaces, and dark color; commonly found near recent volcanic activity.
