igneous
Obsidian
Volcanic Glass (Silica-rich glass)
AI-generated identification · may be incorrectMohs hardness 5 to 5.5, jet black color, vitreous luster, amorphous crystal structure, conchoidal fracture, specific gravity around 2.4.
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Physical properties
Mohs hardness 5 to 5.5, jet black color, vitreous luster, amorphous crystal structure, conchoidal fracture, specific gravity around 2.4.
Formation & geological history
Formed from rapidly cooled felsic lava extruded from volcanic vents, lacking time to form crystal structures.
Uses & applications
Used historically for arrowheads and cutting tools, and currently in ornamental jewelry and occasionally surgical scalpel blades.
Geological facts
Despite its glass-like appearance and lack of minerals, obsidian is considered a natural rock rather than a true mineral.
Field identification & locations
Easily identified by its glassy sheen, dark color, and razor-sharp conchoidal fracture edges; found worldwide in areas of recent volcanic activity.
