igneous
Obsidian
Volcanic Glass (Silica-rich glass)
AI-generated identification · may be incorrectHardness 5-5.5 on the Mohs scale, typically jet black in color, vitreous luster, amorphous crystal structure with conchoidal fracture, and specific gravity around 2.35-2.45.
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Physical properties
Hardness 5-5.5 on the Mohs scale, typically jet black in color, vitreous luster, amorphous crystal structure with conchoidal fracture, and specific gravity around 2.35-2.45.
Formation & geological history
Forms as an extrusive igneous rock when felsic lava cools rapidly with minimal crystal growth, commonly associated with volcanic activity.
Uses & applications
Used historically for sharp cutting tools, arrowheads, and blades, as well as in modern jewelry, ornamental objects, and surgical scalpel blades.
Geological facts
Due to its rapid cooling, obsidian contains no true crystals and is technically a mineraloid rather than a mineral.
Field identification & locations
Easily identified in the field by its glassy sheen, dark color, and sharp conchoidal fracture edges; commonly found near recent volcanic flows worldwide.
