igneous
Obsidian
Volcanic Glass (predominantly SiO2)
AI-generated identification · may be incorrectHardness 5-5.5 on Mohs scale; jet-black, glassy to vitreous luster, conchoidal fracture, and amorphous structure.
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Physical properties
Hardness 5-5.5 on Mohs scale; jet-black, glassy to vitreous luster, conchoidal fracture, and amorphous structure.
Formation & geological history
Forms from the extremely rapid cooling of felsic volcanic lava, which prevents crystal growth.
Uses & applications
Used historically for sharp stone tools and surgical blades; commonly used today in jewelry, decorative carvings, and metaphysical lapidary.
Geological facts
Because it has no crystalline structure, fractured obsidian can produce cutting edges thinner and sharper than modern steel surgical scalpels.
Field identification & locations
Identified by its glossy sheen, deep black color, sharp curved edges, and smooth conchoidal fractures; found near volcanic rhyolite flows.
