igneous
Obsidian
Volcanic Glass
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, glossy black to dark brown color, vitreous luster, amorphous crystal structure with conchoidal fracture.
Identified More igneous →
Explore Obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 5 to 5.5 on the Mohs scale, glossy black to dark brown color, vitreous luster, amorphous crystal structure with conchoidal fracture.
Formation & geological history
Formed as a naturally occurring volcanic glass when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in jewelry, ornamental objects, and occasionally experimental surgical scalpel blades.
Geological facts
Because it cools too quickly to form a crystal structure, obsidian is technically a mineraloid rather than a true mineral.
Field identification & locations
Identified by its intense glassy luster, smooth curved conchoidal fracture edges, and opaque dark coloration; commonly found in regions with recent volcanic activity.
