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 by the rapid cooling of silica-rich lava which inhibits crystal growth. Can be found in volcanic regions of various ages ranging from the Cenozoic to the present.
Uses & applications
Used for making surgical scalpel blades, jewelry, ornamental carvings, and historically for arrowheads and scrapers.
Geological facts
Obsidian is not a true mineral because it is a glass and lacks a crystalline structure. It was widely traded by ancient civilizations for its sharpness which exceeds that of steel.
Field identification & locations
Identify in the field by its smooth glassy texture and extremely sharp conchoidal (shell-like) fracture edges. Found in volcanic areas like the Western US, Mexico, and Iceland.
