igneous
Black Obsidian
Obsidian (Volcanic Glass)
Hardness: 5-5.5 (Mohs scale), Color: Jet black to dark grey, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.35-2.6
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs scale), Color: Jet black to dark grey, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.35-2.6
Formation & geological history
Formed when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. Found in areas of geologically recent volcanic activity, dating from the Cenozoic era.
Uses & applications
Commonly used for making scalpels, jewelry, ornamental carvings, and spiritual collecting. Historically used for arrowheads and cutting tools.
Geological facts
Obsidian is technically a glass, not a mineral, because it lacks a crystal structure. It breaks with extremely sharp edges; obsidian blades can be significantly thinner and sharper than high-quality steel scalpels.
Field identification & locations
Identify by its smooth, glassy texture and distinctive conchoidal (shell-like) fracture patterns. Found in volcanic regions like the American Northwest, Mexico, and Iceland.
