igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness 5-5.5, black or dark green color, vitreous luster, conchoidal fracture, amorphous crystal structure.
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Physical properties
Hardness 5-5.5, black or dark green color, vitreous luster, conchoidal fracture, amorphous crystal structure.
Formation & geological history
Formed from rapidly cooling felsic lava extruded from a volcano, preventing crystal growth.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in jewelry and decorative objects.
Geological facts
Because it contains no crystal structure, it breaks with extremely sharp edges known as conchoidal fractures.
Field identification & locations
Easily identified by its glassy luster and smooth, curved fracture surfaces. Found worldwide in regions with recent volcanic activity.
