igneous
Black obsidian (likely)
Volcanic glass; predominantly silica-rich, non-crystalline silicate glass
AI-generated identification · may be incorrectBlack, glossy vitreous luster with sharp, curved conchoidal fractures; hardness about 5–5.5 Mohs. The image is too small to confirm internal texture or composition.
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Physical properties
Black, glossy vitreous luster with sharp, curved conchoidal fractures; hardness about 5–5.5 Mohs. The image is too small to confirm internal texture or composition.
Formation & geological history
Forms when silica-rich lava cools so rapidly that crystals cannot grow, typically around volcanic flows; its age cannot be determined from the photograph.
Uses & applications
Used for ornamental objects, jewelry, and collectible specimens; historically shaped into blades and tools.
Geological facts
Obsidian is natural volcanic glass, unlike manufactured glass, and can break into exceptionally sharp edges.
Field identification & locations
Look for a glassy sheen and curved, shell-like fracture surfaces; common in volcanic regions such as the western United States, Mexico, Iceland, and Japan. Similar dark glassy materials can be difficult to distinguish visually.
