igneous
Tumbled snowflake obsidian
Obsidian (volcanic glass), SiO₂, with cristobalite spherulites
AI-generated identification · may be incorrectBlack, glassy to vitreous luster with distinctive gray-white snowflake patterns; hardness about 5–5.5 Mohs, amorphous structure, conchoidal fracture, and no cleavage. The pieces appear polished/tumbled.
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Physical properties
Black, glassy to vitreous luster with distinctive gray-white snowflake patterns; hardness about 5–5.5 Mohs, amorphous structure, conchoidal fracture, and no cleavage. The pieces appear polished/tumbled.
Formation & geological history
Rapid cooling of silica-rich rhyolitic lava produced natural volcanic glass; the pale snowflakes formed from radial cristobalite or feldspar crystallization during cooling. It is generally Quaternary to younger, commonly associated with volcanic fields.
Uses & applications
Used for cabochons, beads, carvings, meditation stones, and inexpensive mineral collections; historically, obsidian was knapped into blades and tools.
Geological facts
Snowflake patterns are spherulites rather than fossils or embedded stones. Obsidian can produce exceptionally sharp flakes because of its conchoidal fracture.
Field identification & locations
Identify by its jet-black glassy body, sharp conchoidal fracture, and contrasting rounded gray-white spherulites; common sources include Mexico, the western United States, and Armenia. Confirm with a glassy luster and absence of visible grain boundaries.
