igneous
Black Obsidian
Volcanic Glass (Amorphous SiO2)
AI-generated identification · may be incorrectMohs hardness 5 to 5.5, deep black color, vitreous luster, amorphous crystal structure with conchoidal fracture.
Identified More igneous →
Explore Black Obsidian in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness 5 to 5.5, deep black color, vitreous luster, amorphous crystal structure with conchoidal fracture.
Formation & geological history
Formed from rapidly cooling felsic lava extruded from volcanoes, preventing crystal growth.
Uses & applications
Used for jewelry, decorative objects, metaphysical healing, and historically for sharp cutting tools like arrowheads.
Geological facts
Obsidian lacks a true crystal lattice because it cools too quickly to form minerals, making it a natural mineraloid glass.
Field identification & locations
Easily identified by its jet-black appearance, glass-like shine, and sharp conchoidal fracture edges; found worldwide near recent volcanic activity.
