igneous
Obsidian
Volcanic Glass
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, typically black to dark brown with a vitreous luster and conchoidal fracture.
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Physical properties
Hardness of 5 to 5.5 on the Mohs scale, typically black to dark brown with a vitreous luster and conchoidal fracture.
Formation & geological history
Formed as extrusive igneous rock from rapidly cooling felsic lava without crystal growth.
Uses & applications
Used historically for sharp arrowheads and blades, and modernly in surgical scalpels and jewelry.
Geological facts
Despite being labeled obsidian in the image, the specimen shown is weathered and has a dull, earthy crust unlike typical fresh glassy obsidian.
Field identification & locations
Identify by its characteristic conchoidal fracture and glassy texture when fresh, found globally near recent volcanic activity.
