igneous
Snowflake obsidian
Volcanic glass with cristobalite/spherulitic inclusions; composition typically rhyolitic (silica-rich).
AI-generated identification · may be incorrectBlack, glossy, glassy luster with pale gray “snowflake” patches; amorphous, with no cleavage and conchoidal fracture. Hardness about 5–5.5 Mohs; specific gravity around 2.3–2.6.
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Physical properties
Black, glossy, glassy luster with pale gray “snowflake” patches; amorphous, with no cleavage and conchoidal fracture. Hardness about 5–5.5 Mohs; specific gravity around 2.3–2.6.
Formation & geological history
Forms when silica-rich lava cools rapidly, preventing crystals from developing; the pale patches are crystallized inclusions formed during cooling. Snowflake obsidian is associated with relatively young volcanic deposits, commonly Quaternary.
Uses & applications
Used for carvings, beads, cabochons, and decorative objects; historically, obsidian was shaped into sharp cutting tools.
Geological facts
Obsidian is natural volcanic glass, not a crystalline mineral. Its sharp fracture edges were useful for blades and points.
Field identification & locations
Identify by its shiny black glassy surface, sharp curved fracture, and contrasting gray-white spots; common sources include Mexico and the western United States. The pictured polished specimen appears consistent with snowflake obsidian.
