igneous
Black Obsidian
Volcanic Glass (Amorphous Silicon Dioxide, SiO2)
Hardness: 5-5.5 (Mohs scale); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.4
- Hardness
- 5-5
- Color
- Jet black
- Luster
- Vitreous/Glassy
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
Hardness: 5-5.5 (Mohs scale); Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.4
Formation & geological history
Formed from the rapid cooling of silica-rich rhyolitic lava, which prevents crystal growth. Common in geologically recent volcanic regions.
Uses & applications
Used for ornamental jewelry, surgical scalpel blades, and as decorative gemstones or metaphysical 'healing' stones.
Geological facts
Obsidian is technically a glass rather than a mineral because it lacks a crystal structure. It was widely used by ancient civilizations for stone tools and weapons due to its razor-sharp edges.
Field identification & locations
Identify by its vitreous luster and characteristic curved conchoidal fractures. Commonly found in Iceland, Mexico, and the Western United States.
