igneous
Obsidian
Obsidian (volcanic glass)
Hardness of 5-5.5 on the Mohs scale, deep black color, vitreous (glassy) luster, amorphous (non-crystalline) structure, 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 5-5.5 on the Mohs scale, deep black color, vitreous (glassy) luster, amorphous (non-crystalline) structure, conchoidal fracture.
Formation & geological history
Formed from extrusive igneous rock, specifically when felsic lava cools rapidly with minimal crystal growth.
Uses & applications
Historically used for cutting tools and weapons. Now used in jewelry, decorative items, and sometimes precise surgical scalpels.
Geological facts
Obsidian blades can reach nanometer thinness, making them sharper than steel scalpels.
Field identification & locations
Identify by its glassy texture, black color, and specific conchoidal (shell-like) fracture patterns. Commonly found in areas with past or present volcanic activity.
