igneous
Obsidian
Volcanic Glass (Silica-rich glass)
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, typically jet black with a vitreous luster, amorphous crystal structure, and exhibits sharp conchoidal fracture.
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Physical properties
Hardness of 5 to 5.5 on the Mohs scale, typically jet black with a vitreous luster, amorphous crystal structure, and exhibits sharp conchoidal fracture.
Formation & geological history
Formed as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth, often associated with rhyolitic volcanic flows.
Uses & applications
Historically used for making sharp tools like arrowheads and blades; currently used in jewelry, ornamental objects, and experimental surgical scalpel blades.
Geological facts
Despite appearing black, obsidian is actually rich in silica and can sometimes be translucent or contain trapped gas bubbles that create a golden sheen.
Field identification & locations
Easily identified by its glassy appearance, jet-black color, and extremely sharp curved edges resulting from conchoidal fracture. Found worldwide near volcanic regions.
