igneous
Black Obsidian
Obsidian (Volcanic Glass)
Hardness: 5-5.5 (Mohs), Color: Black to dark gray, Luster: Vitreous/Glassy, Structure: Amorphous (non-crystalline), Fracture: Conchoidal (shell-like)
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (Mohs), Color: Black to dark gray, Luster: Vitreous/Glassy, Structure: Amorphous (non-crystalline), Fracture: Conchoidal (shell-like)
Formation & geological history
Formed when viscous silica-rich lava cools extremely rapidly, preventing the growth of mineral crystals. Typically Neogene to Quaternary in age as it devitrifies over time.
Uses & applications
Used for jewelry, ornamental carvings, high-precision surgical scalpel blades, and metaphysical collecting.
Geological facts
Because it lacks a crystalline structure, obsidian fractures into edges that can be thin enough to be molecularly sharp, significantly sharper than the best steel scalpels.
Field identification & locations
Identify by its deep black color, high gloss, and characteristic curved (conchoidal) fracture lines. Found in volcanic regions like Mexico, Iceland, and the Western USA.
