igneous
Obsidian
Volcanic Glass (Amorphous SiO2)
AI-generated identification · may be incorrectHardness 5-5.5 on Mohs scale, deep dark green to black color, vitreous luster, amorphous crystal structure with conchoidal fracture.
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Physical properties
Hardness 5-5.5 on Mohs scale, deep dark green to black color, vitreous luster, amorphous crystal structure with conchoidal fracture.
Formation & geological history
Formed as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth.
Uses & applications
Used for decorative objects, jewelry, and historically for sharp cutting tools like arrowheads.
Geological facts
Despite being considered a rock, obsidian is actually a mineraloid because it lacks a crystalline structure.
Field identification & locations
Identify by its glassy appearance, sharp curved fracture edges, and smooth texture.
