igneous
Obsidian
Volcanic Glass (Amorphous SiO2)
AI-generated identification · may be incorrectHardness 5-5.5 on Mohs scale, glossy black color, vitreous luster, conchoidal fracture with no crystal structure.
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Physical properties
Hardness 5-5.5 on Mohs scale, glossy black color, vitreous luster, conchoidal fracture with no crystal structure.
Formation & geological history
Formed from rapidly cooling felsic lava extruded from volcanic vents, preventing crystal growth. Found globally in regions with recent volcanic activity.
Uses & applications
Historically used for sharp cutting tools and arrowheads; currently utilized in jewelry, ornamental objects, and experimental surgical scalpel blades.
Geological facts
Obsidian cools so quickly that mineral crystals cannot form, resulting in a naturally occurring glass. When fractured, it yields extremely sharp edges.
Field identification & locations
Easily identified by its glass-like appearance, dark coloration, and distinct conchoidal fracture pattern. Common in western North America and volcanic regions worldwide.
