igneous
Obsidian
Volcanic glass
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, deep black or dark green color, vitreous luster, amorphous crystal structure with distinct conchoidal fracture.
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Physical properties
Hardness of 5 to 5.5 on the Mohs scale, deep black or dark green color, vitreous luster, amorphous crystal structure with distinct conchoidal fracture.
Formation & geological history
Formed as felsic lava cools rapidly with minimal crystal growth, typically associated with viscous rhyolitic lava flows.
Uses & applications
Historically used for sharp cutting tools and arrowheads, and currently valued in lapidary work, jewelry, and specimen collecting.
Geological facts
Despite its glass-like appearance, it is a naturally occurring volcanic rock rather than a true mineral because it lacks a crystalline structure.
Field identification & locations
Easily identified in the field by its glossy surface, dark coloration, and extremely sharp conchoidal fracture edges; found globally near active volcanic areas.
