igneous
Black Obsidian
Volcanic glass
Hardness: 5-5.5 on the Mohs scale, Color: Pitch black, Luster: Vitreous (glassy), Crystal structure: Amorphous (non-crystalline), Cleavage: Conchoidal fracture, Specific gravity: 2.35-2.60
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 on the Mohs scale, Color: Pitch black, Luster: Vitreous (glassy), Crystal structure: Amorphous (non-crystalline), Cleavage: Conchoidal fracture, Specific gravity: 2.35-2.60
Formation & geological history
Formed as an extrusive igneous rock when felsic lava extruded from a volcanic vent cools rapidly with minimal crystal growth.
Uses & applications
Used for making jewelry, ornamental carvings, and historically for sharp cutting tools and arrowheads.
Geological facts
Because it cools so rapidly without forming a crystal structure, obsidian is technically a mineraloid rather than a true mineral.
Field identification & locations
Easily identified by its deep black color, glossy vitreous luster, and sharp conchoidal fracture edges. Found worldwide in areas with past volcanic activity.
