igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness 5 to 5.5 on Mohs scale, black or dark brown color, vitreous luster, amorphous crystal structure, conchoidal fracture, specific gravity around 2.4.
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 5 to 5.5 on Mohs scale, black or dark brown color, vitreous luster, amorphous crystal structure, conchoidal fracture, specific gravity around 2.4.
Formation & geological history
Formed as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in jewelry and ornamental objects.
Geological facts
Despite looking like glass, it is a naturally occurring mineraloid rather than a true mineral because it lacks a crystalline structure.
Field identification & locations
Easily identified in the field by its glass-like appearance, smooth curved conchoidal fractures, and sharp edges.
