igneous
Tumbled snowflake obsidian (probable)
Obsidian, volcanic glass (SiO₂-rich rhyolitic composition), with cristobalite or feldspar spherulites
AI-generated identification · may be incorrectBlack to dark gray, glossy vitreous luster with pale gray-white snowflake patterns; amorphous, conchoidal fracture, no cleavage, hardness about 5–5.5 Mohs, specific gravity about 2.35–2.ใช้. The rounded surface indicates tumbling or polishing.
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Physical properties
Black to dark gray, glossy vitreous luster with pale gray-white snowflake patterns; amorphous, conchoidal fracture, no cleavage, hardness about 5–5.5 Mohs, specific gravity about 2.35–2.ใช้. The rounded surface indicates tumbling or polishing.
Formation & geological history
Rapid cooling of silica-rich lava, preventing crystal growth; the light patches formed from devitrification and spherulitic mineral growth. Most specimens are Cenozoic, commonly associated with young volcanic fields.
Uses & applications
Used for ornamental objects, cabochons, beads, carvings, and lapidary pieces; historically shaped into cutting tools. Common polished specimens have modest collector value.
Geological facts
Snowflake patterns are not fossils or true crystals but radiating aggregates formed as volcanic glass begins to crystallize. The pictured material could also be a dark lapidary stone such as indigo gabbro, so visual identification is not definitive.
Field identification & locations
Look for glassy luster, sharp conchoidal edges, and white-gray rosettes; a streak, hardness, and close inspection can distinguish it from gabbro or dyed stones. Common sources include Mexico, the western United States, and Armenia.
