igneous
Black Obsidian
Volcanic Glass (SiO2 + impurities)
Mohs hardness: 5-5.5, Color: Jet black, 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
Mohs hardness: 5-5.5, Color: Jet black, Luster: Vitreous/glassy, Structure: Amorphous (non-crystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.35-2.6
Formation & geological history
Extrusive igneous rock formed when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. Found in recently active volcanic areas.
Uses & applications
Used for surgical scalpel blades, jewelry (pendants, beads), metaphysical tools, and historically for arrowheads and scrapers.
Geological facts
Obsidian can be sharper than high-quality steel scalpels due to its molecularly thin edge. It was highly prized by Mesoamerican cultures like the Aztecs for weapons and mirrors.
Field identification & locations
Identify by its smooth, glassy texture and razor-sharp conchoidal (shell-like) fracture edges. Commonly found in Oregon, Mexico, and Iceland.
