igneous
Black Obsidian
Volcanic Glass (Amorphous SiO2 with trace impurities)
AI-generated identification · may be incorrectHardness: 5 to 5.5 on the Mohs scale, Color: Pitch black or dark brown, Luster: Vitreous (glassy), Crystal Structure: Amorphous (non-crystalline), Cleavage: Conchoidal, Specific Gravity: 2.35 to 2.60
- Hardness
- 5 to 5
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Physical properties
Hardness: 5 to 5.5 on the Mohs scale, Color: Pitch black or dark brown, Luster: Vitreous (glassy), Crystal Structure: Amorphous (non-crystalline), Cleavage: Conchoidal, Specific Gravity: 2.35 to 2.60
Formation & geological history
Formed as an extrusive igneous rock when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
Uses & applications
Used for making jewelry, ornamental carvings, metaphysical practices, and historically for sharp cutting tools and arrowheads due to its conchoidal fracture.
Geological facts
Because it cools so quickly without forming a crystal lattice, obsidian is technically a mineraloid rather than a true mineral.
Field identification & locations
Easily identified by its deep black color, glass-like shine, and extremely sharp conchoidal fracture edges. Found in regions with recent volcanic activity such as the western United States, Mexico, and Italy.
