Igneous
Obsidian
Obsidian
Hardness: 5-5.5. Color: Black (sometimes with white or gray banding/inclusions). Luster: Vitreous (glassy). Structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture). Specific Gravity: 2.35-2.45.
- Hardness
- 5-5
- Color
- Black (sometimes with white or gray banding/inclusions)
- Luster
- Vitreous (glassy)
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: 5-5.5. Color: Black (sometimes with white or gray banding/inclusions). Luster: Vitreous (glassy). Structure: Amorphous (non-crystalline glass). Cleavage: None (conchoidal fracture). Specific Gravity: 2.35-2.45.
Formation & geological history
Formed by the rapid cooling of viscous lava from volcanoes, preventing crystal formation. Commonly found in areas with recent volcanic activity.
Uses & applications
Historically used for tools, arrowheads, and blades due to sharp edges. Now used in jewelry, surgical scalpels, and as a decorative stone.
Geological facts
Obsidian fractures conchoidally, producing edges thinner than steel scalpels. The white inclusions or banding in this specimen may be Cristobalite (Snowflake Obsidian).
Field identification & locations
Identify by intense glassy luster, black color, lack of crystal structure, and characteristic conchoidal fracture. Found in regions like the western US, Mexico, and volcanic islands.
