mineral
Polished black stone, possibly obsidian or black jasper
Indeterminate; likely volcanic glass (obsidian, SiO₂) or microcrystalline quartz (jasper, SiO₂)
AI-generated identification · may be incorrectSmall, rounded, highly polished dark specimen with a black surface and a brown-gold inclusion or patch. Obsidian has Mohs hardness ~5–5.5, glassy luster and conchoidal fracture; jasper is ~6.5–7, opaque, and usually dull to waxy.
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Physical properties
Small, rounded, highly polished dark specimen with a black surface and a brown-gold inclusion or patch. Obsidian has Mohs hardness ~5–5.5, glassy luster and conchoidal fracture; jasper is ~6.5–7, opaque, and usually dull to waxy.
Formation & geological history
Obsidian forms when silica-rich lava cools rapidly, generally during the Quaternary and younger volcanic activity; jasper forms when silica-rich fluids replace or cement sediments. The image alone cannot establish which material is present.
Uses & applications
Used as a decorative stone, cabochon, bead, carving material, or collectible; obsidian also has historical tool-making significance.
Geological facts
Obsidian is volcanic glass rather than a crystalline mineral, while jasper is cryptocrystalline quartz. The golden area could be iron staining, another mineral inclusion, or reflected light.
Field identification & locations
Check fracture: sharp conchoidal edges and glassy translucence favor obsidian; granular texture, stronger scratch resistance, and opaque waxy appearance favor jasper. Common sources include Mexico, the western United States, and volcanic regions worldwide.
