igneous
Black tumbled stone, possibly obsidian
Obsidian (natural volcanic glass; composition varies, typically silica-rich)
AI-generated identification · may be incorrectSmall, polished, opaque black stone with a glossy surface; hardness about 5–5.5 Mohs, no crystal structure or cleavage. The photo alone cannot reliably distinguish obsidian from other black stones or glass.
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Physical properties
Small, polished, opaque black stone with a glossy surface; hardness about 5–5.5 Mohs, no crystal structure or cleavage. The photo alone cannot reliably distinguish obsidian from other black stones or glass.
Formation & geological history
Obsidian forms when silica-rich lava cools rapidly, preventing crystals from growing; it is generally geologically young and occurs near volcanic flows.
Uses & applications
Commonly made into jewelry, beads, carvings, and collectibles; historically used for sharp-edged tools.
Geological facts
Obsidian breaks with a curved, shell-like (conchoidal) fracture and can form exceptionally sharp edges.
Field identification & locations
Check for natural conchoidal fracture and glassy luster, though a polished piece may be hard to identify visually. Found in volcanic regions worldwide, including Mexico, the western United States, Iceland, and Japan.
