igneous
Black Obsidian
Amorphous volcanic glass (primarily SiO2)
AI-generated identification · may be incorrectHardness: 5-5.5; Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.4
- Hardness
- 5-5
- Color
- Jet black
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-5.5; Color: Jet black; Luster: Vitreous/Glassy; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.4
Formation & geological history
Formed when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. Common in areas of recent volcanic activity.
Uses & applications
Used in jewelry, decorative carvings, and scalpel blades for high-precision surgery due to its ability to hold an edge sharper than steel.
Geological facts
Obsidian was highly prized by ancient cultures for making projectile points and tools. It produces the sharpest edge possible of any known material.
Field identification & locations
Identify by its smooth, glassy surface and characteristic curved (conchoidal) fractures. Found in volcanic regions like the American West, Mexico, and Iceland.
