igneous
Obsidian
Volcanic Glass
AI-generated identification · may be incorrectHardness of 5 to 5.5 on the Mohs scale, typically jet black or dark brown with a vitreous luster, featuring conchoidal fracture.
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Physical properties
Hardness of 5 to 5.5 on the Mohs scale, typically jet black or dark brown with a vitreous luster, featuring conchoidal fracture.
Formation & geological history
Formed as felsic lava cools rapidly with minimal crystal growth, typically in extrusive volcanic environments.
Uses & applications
Used historically for sharp cutting tools and arrowheads, and currently in jewelry, ornamental items, and sometimes surgical scalpel blades.
Geological facts
Despite its glass-like appearance, it is a naturally occurring mineraloid rather than a true mineral because it lacks a crystalline structure.
Field identification & locations
Easily identified by its extremely smooth, curved conchoidal fracture edges and glossy luster; found worldwide near recent volcanic activity.
