igneous
Obsidian (likely blue-sheen or coated obsidian)
Volcanic glass; primarily rhyolitic silica glass (SiO₂-rich, noncrystalline)
AI-generated identification · may be incorrectHardness about 5–5.5 Mohs; black with a vivid blue surface sheen, vitreous luster, conchoidal fracture, and no cleavage. The unusually bright blue band may indicate polishing, artificial coating, or blue-sheen obsidian rather than naturally uniform color.
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Physical properties
Hardness about 5–5.5 Mohs; black with a vivid blue surface sheen, vitreous luster, conchoidal fracture, and no cleavage. The unusually bright blue band may indicate polishing, artificial coating, or blue-sheen obsidian rather than naturally uniform color.
Formation & geological history
Forms when silica-rich lava cools so rapidly that crystals cannot grow, commonly during Quaternary volcanic eruptions. Major sources include Mexico, the western United States, Armenia, and Indonesia.
Uses & applications
Used for ornamental objects, cabochons, carvings, arrowheads, and historically exceptionally sharp cutting tools. This shaped piece appears primarily decorative or collectible.
Geological facts
Obsidian fractures into razor-sharp edges and is technically volcanic glass rather than a crystalline mineral. Blue sheen commonly results from microscopic inclusions or surface treatment.
Field identification & locations
Identify by its glassy appearance, sharp conchoidal fractures, lack of visible crystals, and relatively low density; it should not show the bubbly texture of slag. Natural sheen is usually internal and changes with viewing angle, while coatings may look surface-bound.
